1. Define tissue.

Answer

The tissue is defined as a group of cells which are similar in structure and work together to perform a particular function is known as tissue.

2. In multi-cellular organisms, what is the use of tissues?

Answer

The use of tissue in multi-cellular organisms is to provide structural and mechanical strength as well as to allow division of labour.

3. Mention the types of simple tissues.

Answer

The types of simple tissues are as follows:

➢ Parenchyma

➢ Collenchyma

➢ Sclerenchyma

➢ Aerenchyma

4. Where do we find apical meristem?

Answer

The place where we can find apical meristem is the tip of shoot or root of a plant.

5. _____ tissues make the coconut husk.

Answer

Sclerenchymatous tissue

6. What is phloem made up of?

Answer

It is made up of 4 elements

➢ Sieve tube

➢ Companion cells

➢ Phloem fibres

➢ Phloem parenchyma

7. Which tissue is responsible for the movement of our body?

Answer

A Combination of two tissues is responsible for the movement of our body.

Namely,

➢ Muscular tissue

➢ Nervous tissue

8. What is the structure of a neuron?

Answer

A neuron has a cell body with a nucleus and cytoplasm. From that, long and thin hair like structure arise. Every neuron has one long part known as the axon, and many short and small branched structures known as dendrite. A single nerve cell is known as neuron and some of them may be even a metre long.

9. What is a cardiac muscle? Mention its features as well.

Answer

It is an extremely specialized tissue evolved to pump blood throughout the body.

Features:

➢ They are cylindrical in shape.

➢ They are branched and uninucleated.

➢ Striated muscle fibers.

➢ We cannot control them so they are involuntary.

10. What are areolar tissue’s junctions?

Answer

Areolar tissues are found in animals. They are connective tissues. We can find then between skin and muscles. Also, we can find them around blood vessels and nerves. They are found in bone marrow. The space inside the organs is filled with these tissues. They support internal organs and help to repair tissues.

Short Answer Questions

1. Explain the term tissue.

Answer

A Tissue is defined as a group of cells which perform the same operation and are similar in size and shape (structure).

2. How many elements are needed to make up xylem tissue?

Answer

It requires 4 elements. Namely:

➢ Vessels

➢ Tracheids

➢ Xylem fibres

➢ Xylem parenchyma

3. In plants, what is the difference between simple tissues and complex tissues?

Answer

In the case of simple tissues, they are made up of a single type of cell which performs one common function. Whereas in the case of complex tissues, they are made up of more than one type of cell. They all coordinate to perform one single function.

4. How are parenchyma, collenchyma and sclerenchyma different from each other with respect to cell wall?

Answer

➢ Parenchyma: Thin cell walls which are made up of cellulose.

➢ Collenchyma: Thick cell walls at the corners because of pectin deposition.

➢ Sclerenchyma: Thick cell walls because of lignin deposition.

5. Mention the functions of stomata.

Answer

Cell’s outer layer is known as epidermis and is has pores.These pores are known as stomata. It helps in exchange of gases and transpiration.

6. Give the difference between the types of muscle fibres diagrammatically.

Answer

➢ Cardiac muscles

1. They are present in the heart.

2. They are involuntary.

3. They have 1 nucleus.

4. They are branched.

➢ Smooth muscles

1. They are present in lungs and alimentary canal.

2. They are involuntary.

3. They have 1 nucleus.

4. They are spindle shaped.

➢ Striated muscles

1. Connected with bones

2. They are voluntary.

3. They are long and cylindrical.

4. They have many nuclei.

5. They are un-branched.

7. Mention the cardiac muscle’s specific function.

Answer

➢ They are cylindrical and branched.

➢ They are uninucleated.

➢ Involuntary muscles.

➢ They contract and relax throughout life in rhythm.

8. What is the difference between Striated, un-striated and cardiac muscles on the basis of their structure and location?

9. Draw a diagram of neuron and also label.

10. Answer the following

➢ Name the tissue which forms the inner lining in our mouth.

➢ Name the connecting tissue between muscle and bone.

➢ Name the tissue in plants which transports foods.

➢ Name the tissue which stores fat in human body.

➢ Brain tissue.

➢ Connective tissue whose matrix is fluid Answer

➢ Squamous epithelium

➢ Tendons

➢ Phloem

➢ Areolar tissue

➢ Nervous tissue

➢ Blood

11. Name the type of tissue present in the following

➢ Skin

➢ Bark of tree

➢ Bone

➢ Lining of kidney tubule

➢ Vascular bundle

Answer

➢ Skin: Striated squamous epithelium

➢ Bark of tree: Protective tissue and cork

➢ Bone: Connective tissue

➢ Lining of kidney tubule: Cuboidal epithelium tissue

➢ Vascular bundle: Conducting tissue

12. Where is parenchyma tissue present?

Answer

It is present in the pith of stems and roots. It is called chlorenchyma when it contains chlorophyll. It is present in green leaves. In the case of aquatic plants, parenchyma is present which contains huge air cavities. That helps them in floating. Such parenchyma tissues are known as aerenchyma.

13. In plants, what is the function of epidermis?

Answer

It forms a continuous layer which is without inter-cellular spaces. It provides protection.

14. How can the cork act as a protective tissue in plants?

Answer

Cork cells are dead. They are arranged very closely so that there is no inter-cellular space. There is deposition of suberin on the walls which make them impervious to water and gases.

15. Complete the table.

Multiple Choice Questions

a) Cork cells are dead. They have a chemical in their walls which makes them impervious to water and gases. Which is that chemical?

i. Suberin

ii. Wax

iii. Cutin

iv. Lignin

b) Due to ___ tissue, there is flexibility in plants.

i. Parenchyma

ii. Chlorenchyma

iii. Collenchyma

iv. Sclerenchyma

c) Which tissue is present in ducts of salivary glands and in the lining of kidney tubules?

i. Squamous epithelium tissue

ii. Columnar epithelium tissue

iii. Glandular epithelium tissue

iv. Cuboidal epithelium tissue

d) The tissue connecting muscles to bones is ____.

i. Areolar

ii. Tendon

iii. Ligament

iv. Cartilage

e) Which tissue helps with the movement of our body?

i. Skeletal tissue

ii. Muscular tissue

iii. Nervuos tissue

iv. All

f) Monocyte, neutrophil, basophil and eosinophil are types of __________.

i. White blood cells

ii. Compact bone

iii. Red blood cells

iv. Areolar tissues

g) To which of category of muscular tissues, do spindle shaped, un-branched and uni-nucleated cells belong to?

i. Smooth cells

ii. Cardiac cells

iii. Striated cells

iv. (i) and (iii) both

h) In ____ , companion cells as well as sieve cells are present.

i. Cambium

ii. Xylem

iii. Cork

iv. Phloem

i) Due to ____, the size of stem increases in width.

i. Lateral meristem

ii. Intercalary meristem

iii. Apical meristem

iv. Primary meristem

j) Lymph and blood are ____ types of tissues.

i. Permanent

ii. Epithelial

iii. Muscular

iv. Connective

k) Bone and cartilage are examples of ___ type of tissue.

i. Epithelial

ii. Connective

iii. Muscular

iv. Meristematic

l) To which category of tissues do xylem and phloem belong to?

i. Complex

ii. Simple

iii. Epidermal

iv. Protective

m) Cells of _____ tissues are capable of dividing and re-dividing.

i. Meristematic

ii. Connective

iii. Complex

iv. Protective

n) _____ tissue helps in the absorption and secretion. It is present in the inner lining of the alimentary canal.

i. Columnar epithelium

ii. Cuboidal epithelium

iii. Ciliated epithelium

iv. Squamous epithelium

Answers

a) i

b) iii

c) iv

d) ii

e) iv

f) i

g) i

h) iv

i) i

j) iv

k) ii

l) i

m) i

n) i

Very Short Questions

1. Which tissue is responsible for the movement of our body?

Answer

Nervous tissue as well as muscle tissue

2. What is the structure of a neuron?

Answer

The unit cell or the building block of a nervous tissue is a neuron. It has a thread-like structure with axon and cell body.

3. Mention the types of simple and complex tissues.

Answer

Simple:

➢ Sclerenchyma

➢ Parenchyma

➢ Collenchyma

Complex:

➢ Phloem

➢ Xylem

4. Apical meristem is found in _____.

Answer

It is found in the growing tips of root and stem. The length of root and stem is increased due to the presence of Apical meristem.

5. Which tissue is present in the husk of a coconut?

Answer

Sclerenchyma

6. Name the elements of phloem.

Answer

➢ Sieve tubes

➢ Phloem parenchyma

➢ Companion cells

➢ Phloem fibres

7. What do you mean by aerenchyma?

Answer

Cells with large air- filled cavities of parenchyma are known as aerenchyma. It helps aquatic animals to float.

8. What are the major functions of tissues in multi-cellular organisms?

Answer

It helps organisms in growth. It also helps in performance and organization of various organs.

9. What are the two types of tissues?

Answer

➢ Animal tissues

➢ Plant tissues

10. Mention the two types of plant tissues.

Answer

➢ Permanent tissue

➢ Meristematic tissue

11. Define differentiation.

Answer

Differentiation is defined as the process in which cells take up permanent size, shape and function.

12. Give the types of meristematic tissues.

Answer

➢ Intercalary tissue – nodes

➢ Apical tissue – tips of shoot and root

➢ Lateral tissue – stem sides

13. Where do you think apical tissues are found?

Answer

Tips of stems and roots

14. Apical tissues are present at the lateral surface of the stem. Is the above statement true? If not, why?

Answer

False

Lateral tissues are present at the lateral surface.

15. Name the tissues which are present in the plants at the nodes.

Answer

Intercalary tissue

16. Mention the different types of blood cells Answer

➢ WBCs

➢ RBCs

➢ Platelets

17. Define tracheids.

Answer

Tracheids have tapering ends and are basically elongated cells.

18. Define guard cells

Answer

Guard cells are kidney – shaped epidermal cells and a pair of these cells bound each stomata.

19. True or false The simplest tissue is epithelial tissue.

Answer

True

20. Mention the functions of Cuboidal epithelium

Answer

➢ Absorption

➢ Excretion

➢ Secretion

➢ Mechanical support

Short Answer Question

1. Differenciate between bone and cartilage Answer Bone Cartilage

2. Mention the functions of bone.

Answer

➢ Provides skeletal support

➢ Provides shape to body

➢ Protects the essential organs

➢ Anchors muscles

3. Mention the functions of cartilage.

Answer

➢ Support to the body

➢ Flexibility

➢ At joints, smoothens surface

4. Complete the sentences.

1. _____ conducts minerals and water.

2. _____ conducts food in higher plants.

3. Blood is a ____ type of tissue.

4. Bone has ____ cells.

5. Cartilage has ____ cells.

6. The connective tissue where fibres are not present is ________

Answers

1. Xylem

2. Phloem

3. Connective

4. Osteocyte

5. Chondrocyte

6. Blood

5. Mention the functions of the areolar tissue.

Answer

➢ Helps to repair tissues after any injury.

➢ Fixes skin of underlying muscles.

➢ Helps in combating outside toxins.

6. Differentiate between phloem and xylem.

Answer

7. Define fibres.

Answer

Fibres are those which are made up of narrow, very long and thick cells.

8. Name the following tissues.

a) Which tissue covers the external surface in animals?

b) Which tissue stores fat in animals?

c) Which tissue joins bone to bone?

d) Which tissue divides and re – divides and responsible for growth in plants?

Answer

a) Epithelial tissue

b) Adipose tissue

c) Ligament

d) Meristematic tissue

9. Define stomata.

Answer

They are small holes or pores on the surface of leaves which helps in exchange of gases and also in transpiration.

10. Epidermal tissue does not have intercellular space. Why?

Answer

This tissue forms a protective layer for plants and helps to protect the internal parts of plants. It protects th plant from loss of water, attack by parasitic fungi and mechanical injury.

11. Name and mention the function of each xylem cell

Answer

Xylem consists of the following:

➢ Xylem parenchyma

➢ Xylem fibres

➢ Vessels

➢ Tracheids Functions of xylem are as follows:

➢ Xylem parenchyma – It stores food. It also helps in sideways flow of water.

➢ Xylem fibres – They are supportive

➢ Tracheids and vessels – They help in transportation of minerals and water.

12. What are the functions of stratified squamous epithelium? Also, mention its location.

Answer

They are found in the skin. They are present in layers to prevent wear and tear.

13. Differentiate between tendon and ligament.

Answer

Tendon Ligament Strong and flexible Elastic and flexible Connects bone to muscles Connects bone to bone

14. Differentiate between striated muscles and un – striated muscles.

Answer

Striated muscles Un – striated muscles Voluntary muscles Involuntary muscles Shows alternate light and dark Such bands are not present bands Skeletal muscles Smooth muscles They are cylindrical They are tapering They are multinucleated They are uninucleated

15. Differentiate between blood and bone.

Answer

16. What are the different types of tissues which are present in animals?

Answer

➢ Nervous tissue: It consists of nerve cells and they are present in nervous system.

➢ Muscular tissue: It is made up of muscles and they help in movement of our body.

➢ Epithelial tissue: They are found in the inner and outer lining of our body.

➢ Connective tissue: They connect various organs of our body.

17. Blood is called the connective tissue. Give reason.

Answer

Blood is made up of cells and plasma. Plasma is a fluid. Red blood cells, white blood cells and platelets cells are also present in blood. All these cells are connected because of plasma. Blood also transports water and food to various parts of our body and connects them.

18. Name the types of muscle tissues and also mention the functions of these tissues.

Answer

There are three types of muscle tissues.

➢ Smooth muscle

➢ Striated muscle

➢ Cardiac muscle

Functions

➢ Smooth muscle Involuntary muscle, controls the flow of food in the alimentary canal,   relaxation and contraction of blood vessels. They are present in the uterus, iris, etc.

➢ Striated muscle They have alternate dark and light bands. They are found in skeletal tissues. They are involuntary muscles. They help in the movement of bones and body.

➢ Cardiac muscle They are found in the heart. They help in the rhythmic contraction and relaxation of our heart throughout our life.

19. Differentiate between collenchyma, parenchyma and sclerenchyma.

Answer

20. Differentiate between striated muscle, cardiac muscle and smooth muscle.

Answer

Striated muscle	Cardiac muscle	Smooth muscle
Cells are cylindrical, long and un – branched.	Cells are cylindrical and branched.	Cells are long with pointed ends. They are un – branched.
Cell is multinucleated.	Cells are uninucleated.	Cells are uninucleated.
Cells have alternate dark and light bands.	Cells have alternate light and dark bands.	Cells do not have alternate light and dark bands.
Voluntarily controlled.	Involuntarily controlled.	Involuntarily controlled.
Attached to bones.	Present in the wall of our heart.	Found in stomach and blood vessels.
Contracts quickly. It cannot remain contracted for a longer time, so gets tired.	Contracts quickly rhythmically so do not get tired.	Contracts slowly. It can remain contracted for a a longer time, so do not get tired.

21. What are the different types of meristematic tissue? Also, mention their functions. Draw a diagram of the tissue to show its location.

Answer

There are three types of meristematic tissues namely:

➢ Apical meristem: Growth in length

➢ Lateral meristem: Growth in breadth or thickness

➢ Intercalary meristem: Growth in inter – nodes

22. Explain the structure of a nervous tissue with details about its location and function.

Answer

Structure:

It consists of nerve cells joined end to end. A nerve cell has a cell body with cytoplasm and nucleus. From that, long and thin hair like structure arise. Every neuron has one long part known as the axon, and many short and small branched structures known as dendrite. A single nerve cell is known as a neuron and sometimes may even be a metre long.

Location:

Nervous tissue is found in spinal cord, brain and nerves.

Function:

Nervous tissue is the basic element of our nervous system. These are specialized cells that does the function of exchanging information. Nervous tissue transmits and receives stimuli from one organ to another organ in the body. These cells allow moving muscles and react to stimuli.

23. Draw the flow chart of a plant tissue and an animal tissue.

Answer

➢ Plant tissue

➢ Animal tissue

24. Differentiate between a plant cell and an animal cell.

Answer

Long Answer Questions

1. Explain plant tissue in detail.

Answer

Plant tissue is mainly divided into two categories.

➢ Meristematic tissue

➢ Permanent tissue

Meristematic tissue:

The cells divide very fast. It helps in the growth of the plants. The shape of the cell is oval, round and polygonal. There is no inter – cellular space.

There are three types of meristematic tissue:

➢ Apical meristem: Growth in length

➢ Lateral meristem: Growth in breadth or thickness

➢ Intercalary meristem: Growth in inter – nodes

Permanent tissue: When meristematic tissue stops dividing and gets mature, then it forms permanent tissue.

There are two types of permanent tissue:

➢ Simple tissue

➢ Complex tissue Simple Tissue They are same in structure and perform the same function.

There are three types of simple tissue:

➢ Parenchyma: It is present in soft parts.

➢ Collenchyma: It provides mechanical strength to plants and is found in stalks.

➢ Sclerenchyma: It provides support as well as flexibility to plants.

Complex tissue

They are different in structure but together , perform the same function.

There are two types of complex tissue:

➢ Xylem: It transports water from root to shoot in plants. Its elements are tracheids, xylem sclerenchyma, xylem parenchyma, vessel elements.

➢ Phloem: Transports food to all parts of the plant. Its elements are sieve tubes, phloem parenchyma, companion cells and intermediary cells.

2. Explain connective tissue along with its types.

Answer

Connective tissue consists of various types of cells. They all perform the same function. There are three types of connective tissue.

➢ Proper connective tissue

➢ Fluid tissue

➢ Skeletal tissue Proper connective tissue is comprised of four types:

➢ Areolar and ligament connective tissue: It is present between muscles and skin and in the bone marrow. It is also present around nerves and blood vessels. They fill the space inside the organs. It helps to repair tissues. They also provide strength to internal organs.

➢ Adipose tissue: It stores fat. It is found below the skin and also between internal organs. These tissues are packed with fat globules. Due to this fat storage, it behaves as an insulator.

➢ Tendon: It is fibrous, strong and flexible. It joins muscles with bone.

➢ Ligament: It is elastic and strong. It joins bone with bone.

Fluid tissue consists of:

➢ Blood: It is a liquid tissue called plasma. It helps to transport substances like gases, hormones, digested food and waste material. It has RBC, WBC, plasma and blood platelets.

➢ Lymph: It transports digested fat and white blood cells in plasma.

Skeletal tissue is made up of:

➢ Bone: It is a hard tissue. It helps in the movement and support of our body. It is a non – flexible tissue.

➢ Cartilage: It smoothens the bone surface at joints. It is found in our ear, nose, trachea and larynx.

3. Explain epidermis in plants.

Answer

It forms the outermost layer of the plant. It is comprised of a single cell layer. This tissue forms a protective layer for plants and that helps to protect the internal parts of plants. It helps in protection against loss of water, attack by parasitic fungi and mechanical injury.

Epidermis has small pores known as stomata. They are small holes or pores on the surface of leaves which help in exchange of gases and also in transpiration.

Epidermis has long parts like hair that provide greater surface area for water absorption in roots. In plants found in deserts,epidermis consists of a thick waxy coating called cutin which makes the outer layer water resistant.

4. Decribe complex tissue in plants.

Answer

Generally, complex tissues consist of more than one type of cell.They are different in structure but together perform the same function.

There are two types of complex tissues:

They both are conductive tissues and form the vascular bundle.

➢ Xylem: It transports water from root to shoot in plants. The movement is only in one direction that is, from roots to shoot. It provides mechanical support to the plant. It has mostly dead elements. Its elements are tracheids, xylem sclerenchyma, xylem parenchyma, vessel elements.

➢ Phloem: Conduct food to all parts of the plant. The movement of phloem is bidirectional that is, movement in both the directions is possible. Its elements are mostly living. Its elements are sieve tubes, phloem parenchyma, companion cells and intermediary cells.

Activity

1. Take two jars of glass filled with water.Take 2 onion bulbs. Place one on each jar.

Observe the roots in both the bulbs for a few days.
On day 1, 2 and 3 measure the lengths of the roots.
Cut root tips by approx 1 cm on day 4 in jar 2. After that, observe the growth of roots and measure their length every day in both the jars.
From the observation, answer the questions.
a) Which onion has the longest root? Give the reason?
b) The roots continue growing even after cutting the tips of plant. True or false? Explain with reason.

Answer

a) Jar 1 has the longest root because roots continue to grow as the root tips are very intact.

b) False, in jar 2 when onion tips were cut it stopped growing. The reason behind that is the root tip contains meristematic tissues which are responsible for the growth of plant but those tissues were removed with the tip so it stopped growing.

2. Take a plant. Cut the stem into very thin sections or slices. Stain slices with safranin and put one nicely cut slice on a slide and put a drop of glycerine on the slice.
Cover it with cover – slip. Observe under microscope. Observe different types of cells and also see their arrangement.

Answer the questions from your observation.

a) Are the structures of all cells similar?

b) How many types of cells can be observed?

c) Why are there so many types of cells? Give reason.

Answer

a) No, all cells are different. They have different sizes and shapes.

b) There are at least 10 different types of cells present in the slide.

c) There are many types of cells in plants with different size and shape. They all have specific roles to play in the overall growth of the plant.

3. Pluck a leaf of Rheo.Break it with pressure after stretching. Stretch it gently while breaking so that some skin or peel comes out from the cut surface. Remove this skin. Put it in a Petri dish which is filled with water. Add safranin. Transfer it on a slide after waiting for few minutes. Place a cover – slip it on gently.

Answer

We can see epidermal cells with stomata pores under slide as shown in the figure.

When we see stomata pores under a microscope, we can see stomata pores and guard cells as shown in the figure given below.

Value based Questions

1. Students completed a project in which they had to find botanical names of the trees in the campus. They carved the name of the plants on a metal plate and fixed it on the trunk of the respective trees. Shreyash was worried that while fixing the plate, many cells are bound to get damaged. Then his teacher explained him that the outer layer of the trunk is not living, in fact nothing will happen to the trees.

a) On the outer layer, which type of cells are present on the bark of a tree?

b) Cork behaves as a protective tissue. How?

c) What moral values are seen in the students’ behavior from the incident above?

Answer

a) The outer layer of the bark or trunk of the tree has dead cells which behave as a protective layer for trees.

b) Cork behaves as a protective tissue because it has dead cells and they do not have any inter – cellular space. They are closely packed. Cell walls have depositions of suberin.

c) The students show team effort, co – operation and care for nature.

2. There was a paralytic patient who could not walk. Family members took utmost care of the patient.

a) Which tissues are responsible for the movement of the body?

b) Which tissues are present in spine and brain?

Answer

a) Muscular tissues and nervous tissues are responsible for the movement of the body.

b) Nervous tissues are present in spine and brain.

1) Who discovered cells, and how was it discovered ?

Answer:

Robert Hooke discovered cells in 1665 while examining a thin slice of cork through a self-designed microscope. He saw that the cork resembled the structure of a honey comb consisting of many little compartments. Those small boxes are called cells.

2) Why the cell is called the structural and Junctional unit of life?

Answer:

A cell is capable of carrying out all necessary activities of life independently. So, they are called functional or basic unit of life.

3) How do substances like CO₂ and water move in and out of the cell? Discuss.

Answer:

CO₂ moves by diffusion and H₂O  move by osmosis through cell membrane.

4) Why is the plasma membrane called a selectively permeable membrane?

Answer:

It is so called selectively permeable membrane because it allows only the entry and exit of some substances, not all.

5) Provide the differences between prokaryotic and eukaryotic cells.

6) Name two organelles we have studied that contain their own genetic material?

Answer:

The two organelles which have their own genetic material are:

1. Mitochondria

2. Plastids

7) If the organisation of a cell is destroyed due to some physical or chemical influence, what will that result in?

Answer:

The cell will not be able to revive and lysosomes will digest it.

8) Why are lysosomes known as suicide hags?

Answer:

When the cell gets damaged, lysosomes may burst, and the enzymes digest their own cell. Therefore lysosomes are known as suicide bags.

9) Where are proteins synthesised inside the cell?

Answer:

The proteins are synthesised in the ribosornes that are also known as protein factories.

10) Provide the difference for prokaryotic cell for its difference with eukaryotic cell?

Answer:

Prokaryotic cell is generally smaller in size (1-10 pm), nuclear region is poorly defined and the cell organelles are not membrane-bound and has a single chromosome. Eukaryotic cell is generally larger in size (5-100 pm), nuclear region is well defined with nuclear membrane. Membrane-bound cell organelles are present and it has more than one chromosome.

11) What would happen if the plasma membrane ruptures or breaks down?

Answer:

If plasma membrane ruptures or breaks down then molecules of some substances will freely move in and out.

12) What would happen to the life of a cell if there was no Golgi apparatus?

Answer:

Golgi apparatus has the function of storage, modification and packaging of the products in vesicles. If there were no Golgi bodies, packaging and dispatching of materials synthesised by the cell will be stocked.

13) Which organelle is known as the powerhouse of the cell? Why?

Answer:

Mitochondria is known as powerhouse of the cell because it releases the energy required for different activities of life.

14) Where do the lipids and proteins constituting the cell membrane get synthesised?

Answer:

Lipids and proteins are synthesised in ER [Endoplasmic Reticulum].

15) How does Amoeba obtain it’s food?

Answer:

Amoeba take it’s food by the cell membrane which forms the food vacuole.

16) What is osmosis?

Answer:

Osmosis is the process of movement of water molecule from a region of higher concentration through semi-permeable membrane to a region of lower water concentration.

SHORT ANSWER TYPE QUESTIONS

1) What are plastids? Name the different types of plastids found in plant cell.

Answer:

Plastids are organelles found only in plants. They are:

(a) Chloroplast-Containing chlorophyll

(b) Chromoplast-Containing carotenoids and xanthophyll (coloured plastids)

(c) Leucoplast-Wllite or colourless plastids

2) What is plasma membrane made up of?

Answer:

Plasma membrane is made up of proteins and lipids.

3) What did Robert Hooke observed first in cork cell?

Answer:

Robert Hooke observed that cork consists of box like compartments which formed a honeycomb structure.

4) Name the autonomous organelles in the cell.

Answer:

Chloroplasts and mitochondria are the autonomous organelles in the cells.

5) What does protoplasm refer to?

Answer:

Protoplasm refer to cytoplasm and nucleus.

6) Name two cells which keep changing their shape.

Answer:

Amoeba and white blood cells.

7) Name the smallest cell and the longest cell in human body.

Answer:

The smallest cell is the red blood cell or sperm cell in male. Longest cell is the nerve cell.

8) Name 3 features seen/present in almost every cell.

Answer:

Plasma membrane, nucleus and cytoplasm.

9) What is diffusion?

Answer:

When gases like CO2, 02, move across the cell membrane, this process is called diffusion.

10) What is osmosis? How does it take place ?

Answer:

The movement of water molecules through a selectively permeable membrane is called osmosis. This takes place from high water concentration to low water concentration.

11) What is the full form of DNA?

Answer:

DNA —> Deoxyribo Nucleic Acid.

12) What is the function of chromosome?

Answer:

Chromosomes contain information for the inheritance of features from parents to next generation in the form of DNA molecules.

13) Name the organelles present in liver of animals which detoxifies many poisons and drugs.

Answer :

In the liver of animal cells smooth endoplasmic reticulum helps in detoxifying many poisons and drugs.

14) What is the energy currency of the cell?

Answer : ATP—Adenosine Triphosphate.

15) What is the function of ribosome?

Answer: Ribosomes help in protein synthesis.

16) Where are genes located in the cell?

Answer: Genes are located in the chromosomes in the nucleus of the cell.

17) Name the cell organelles that helps in packaging?

Answer: Golgi apparatus.

18) Name the cell organelle which helps in the transportation of material.

Answer : Encloplasmic reticulum.

19) Name the cell organelle due to which leaves, flowers and fruits get their colour.

Answer: Chromoplast.

20) Name the cell organelle which helps in the formation of lysosome.

Answer : Golgi apparatus.

21) Name the cleansing organelle in the cell.  

Answer: Lysosomes.

22) Name two cells with cell wall.

Answer : Onion cell (plant cell) and fungi.

23) Why does mitochondria have largely folded inner membrane?

Answer:

Mitochondria is the site for cellular respiration and provides energy to the cell. The largely folded inner membrane provides the increased surface area for ATP-generating chemical reactions.

24) Which organelle makes the digestive enzyme of lysosome?

Answer: Rough endoplasmic reticulum makes the digestive enzyme of lysosomes.

25) What are cisterns?

Answer:

The golgi bodies consist Of a system of membrane-bound vesicles arranged in stacks called cisterns.

Short Answer Type Questions 

1) State two conditions required for osmosis.

Answer:

(i) The difference in the concentration of water, one should have higher concentration than the other.

(ii) Semi-permeable membrane is also required through which water will flow.

2) What is plasmolysis?

Answer:

There is shrinkage or contraction of the contents of the cell away from the cell wall, through osmosis , when a living plant cell loses water. This is known as plasmolysis.

3) How do fungi and bacteria can withstand much greater changes in the surrounding medium than animal cells?

Answer:

The cell wall present in fungi and bacteria permits these cells to withstand very dilute externalmedium without bursting. The cells take up water by osmosis, swells, and builds the pressure against the cell wall. Then wall exerts an equal pressure against the swollen cell. It is because of the cell wall, such type of cells can withstand greater changes in the surrounding medium than that of animal cells.

4) Give the function of nuclear membrane.

Answer:

The nuclear membrane present as outer covering in the nucleus allows the transfer of material inside and out of the nucleus to cytoplasm.

5) Name the cell-organelles that have their own DNA and ribosomes.

Answer :

The cell organelles with their own DNA and ribosomes are mitochondria and plastids.

6) What is endocytosis?

Answer:

The cell membranes flexibility allows the cell engulf in food and other material from its external environment. This process is known as endocytosis.

7) What is the function of vacuoles?

Answer:

Vacuoles are storage sacs for solid or liquid content. In plant cells it provides turgidity and rigidity to the cell. In single-celled organisms vacuoles store food, e.g., Amoeba.

8) When we put raisins in water, why do they swell?

Answer:

Raisins are dry with less water inside, when they are kept in water, osmosis takes place, water flows through the cell wall, cell membrane of the raisins and therefore it swells.

9) Why are lysosomes called suicidal bags?

Answer:

Lysosomes contain digestive enzymes in it and helps in the cleaning of cell by digesting any foreign materials entering the cell, such as bacteria, food and old cell organelles. When the lysosomes burst, the digestive enzyme digest its own cell. Hence it is called as suicidal bag.

10) What is nucleoid?

Answer:

The nuclear region in some cells are poorly defined due to the absence of a nuclear membrane , it contains only nucleic acid. This undefined nuclear region with nucleic acid in it is called nucleoid.

11) What is the role of cell organelles in the cell?

Answer:

Each kind of cell organelles performs a specific function such as making new material, clearing of the waste, transporting material, etc.

12) What is the function of nucleus in a cell?

Answer:

The nucleus plays a very important role in the reproduction of cells. It also helps the single cell to divide and form two new daughter cells. It plays an important role in determining how the cell will develop and what form it will exhibit at maturity, by directing the chemical activities of the cell.

13) What is the junction of plastids?

Answer:

Plastids are present only in plant cells. There are two types of plastids chromoplasts (coloured plastids) and leucoplasts (white or colourless) Chromoplast—Consists of coloured pigments and gives different colours to flowers, fruits and leaves. The green colour pigment present in leaf is called chlorophyll which helps in the photosynthesis and a plastid with chlorophyll is called chloroplast. Leucoplast—It stores starch, oil and protein granules in it.

14) Do vacuoles store some material? If yes, name them.

Answer:

Yes, vacuoles also store some important substances required in life of the plant cell. These are amino acids, sugars, various organic acids and some proteins. In some unicellular organisms, e.g. Amoeba, vacuoles also store food.

15) Explain the structure and function of Golgi bodies.

Answer:

Structures: Golgi bodies consist of a system of membrane-bound vesicles arranged in stacks parallel to each other called cisterns. These membranes have connections with the membrane of endoplasmic reticulum (ER). Functions:

(1) It also stores, modifies and helps in the packaging of products in vesicles.

(2) In some cases, complex sugars may be made from simple sugars in it.

(3) It also helps in the formation of lysosomes.

16) What are ribosomes? Where are they located in the cell? What is their function?

Answer:

Ribosomes are spherical organelles present in the cell which are either freely distributed in the cytoplasm or may be attached to the endoplasmic reticulum. It consists of ribosomal RNA (Ribonucleic acid) and proteins. Functions of Ribosomes: It helps in the synthesis of proteins.

17) What is the difference in chromatin, chromosomes and gene?

Answer:

(1) Chromatin: It is a fine network of thread-like structure made up of DNA or RNA. It gets condense to form chromosomes.

(2) Chromosome: The chromosomes are made from chromatin material and are located in the cell.

(3) Genes are found in chromosomes.

18) Why do plant cells have more in number and big-sized vacuoles as compared to the animal cells?

Answer:

Plant cells attain turgidity and rigidity due to the more number of vacuoles as well as large-sized vacuoles help the plant cells to withstand the wear and tear, external environmental conditions. They also help in the storage of essential material required by plants for their growth like amino acids, sugar and various organic substances.

19) Explain the following (a) Plasma membrane (b) Cytoplasm (c) Nucleus.

Answer:

(a) Plasma membrane: It is a thin membrane which controls the passage of materials in and out of the cell. It is otherwise called as selectively permeable membrane. It makes the outer boundary of the cell and is made up of lipo-protein

(b) Cytoplasm: It is transparent jelly-like thick substance present inside the cell. It forms the ground of the cellwithin which all the cell organelles are suspended.

(c) Nucleus: It is a double-layered membrane structure which contains chromosomes required for the inheritance of characteristics from one generation to the other.

20) What is membrane biogenesis?

Answer:

The endoplasmic reticulum helps in the manufacture of proteins and fat molecules which are important for function of the cell. These proteins and lipids help in the building of the cell membrane. This process is known as membrane biogenesis.

21) Which is known as powerhouse of the cell?

Answer:

Mitochondria is known as powerhouse of the cell because they store energy in the form of ATP. [Adenosine Triphosphate]

22) What is meant by gene?

Answer:

It is a segment of DNA. They are located on chromosomes in linear fashions. One gene may perform one or more function. Genes are carrier of genetic codes.

23) State two conditions which are required for osmosis.

Answer:

(i) The difference in the concentration of water, one should have higher concentration than the other.

(ii) Semi-permeable membrane is also required through which water will flow.

24) How does bacteria and fungi can withstand much great changes in surrounding medium than that of animal cells?

Answer:

The cell wall present in fungi and bacteria permits these cells to withstand very dilute external medium without bursting. They take up water by osmosis, and builds the pressure against the cell wall. This is because of the cell wall, such cells could withstand great changes in surrounding medium than that of animal cells.

25) Give the function of nuclear membrane.

Answer :

The nuclear membrane present as outer covering of nucleus allows transfer of material inside and also out of the nucleus to cytoplasm.

26) Name the cell-organelles that have their own DNA and ribosomes.

Answer:

The cell organelles with their own DNA and ribosomes are mitochondria and plastids.

27) What is endocytosis?

Answer:

The cell membranes flexibility allows the cell engulf in food and other material from its external environment. This process is called as endocytosis. Example : Amoeba acquires its food through such processes.

28) What is the function of vacuoles?

Answer:

Vacuoles are storage sacs for solid otherwise liquid content. In the plant cells it provides rigidity and turgidity to the cell. In single celled organisms vacuoles store food, e.g., Amoeba.

29) When we put raisins in water, why do they swell?

Answer:

Raisins are dry due to less water inside, but when they are kept in water, osmosis takes place, water flows through the cell wall, cell membrane of the raisins and therefore it swells.

30) Why are lysosomes called suicidal bags?

Answer:

When the lysosomes burst, the digestive enzyme digest its own cell. Hence it is called as suicidal bag.

31) What is nucleoid?

Answer:

The nuclear region in some cells are poorly defined due to the absence of a nuclear membrane, it contains only nucleic acid. This undefined nuclear region with nucleic acid in it is called nucleoid.

32) What is the role, of cell organelles in the cell?

Answer:

Each kind of cell organelles perform specific function such as making new material, clearing of the waste, transporting material, etc.

33) What is the function of nucleus in a cell?

Answer:

The nucleus plays a very important role in the reproduction of cells It helps a single cell to divide and form two new daughter cells. It plays an important role in determining how the cell will develop and what form it will exhibit at maturity, by directing the chemical activities of the cell.

34) What is the Junction of plastids?

Answer:

Plastids are present only in plant cells. There are two types of plastids and Chromoplast—Consists of coloured pigments and gives different colours to flowers, fruits and leaves. The green colour pigment present in the leaf is called as chlorophyll and it helps in the photosynthesis and a plastid with chlorophyll is called chloroplast. Leucoplast—It stores starch, oil and protein granules in it.

35) Does vacuoles store material? If so, name them.

Answer:

Yes, vacuoles store some important substances required in life of the plant cell. These are amino acids, sugars, various organic acids and also some proteins.Example., Amoeba, vacuoles also store food.

36) Explain the structure and function of Golgi bodies.

Answer:

Structures: Golgi bodies are bodies which consist of membrane bound vesicles arranged in form of stacks parallel to each other called cisterns. These membranes have connections with the membrane of endoplasmic reticulum (ER).

Functions:

(1) Material synthesized near the ER is packed and then dispatched to the target inside and outside the cell through Golgi apparatus.

(2) It also helps in the formation of lysosomes.

37) What are ribosomes? Where are ribosomes located in the cell? What is their function?

Answer:

Ribosomes are spherical organelles present in the cell which are either freely distributed in the cytoplasm or may be attached to the endoplasmic reticulum. It has ribosomal RNA (Ribonucleic acid) and proteins. Functions of Ribosomes: It helps in the synthesis of proteins.

38) What is the difference in between chromosomes, chromatin and gene?

Answer:

(1) Chromosome: The chromosomes are made from chromatin material and are located in the cell.

(2) Chromatin: It is a fine network of thread-like structure made up of DNA or RNA. It gets condense to form chromosomes.

(3) Genes are found in chromosomes.

39) Why do plant cells have more in number and big-sized vacuoles as compared to the animal cells?

Answer:

Plant cells attain turgidity and rigidity due to the more number of vacuoles as well as large-sized vacuoles help the plant cells to withstand the wear and tear, external environmental conditions. They also help in the storage of essential material required by plants for their growth like amino acids, sugar and various organic substances.

40) Explain the following terms: (a) Plasma membrane (b) Cytoplasm (c) Nucleus.

Answer:

(a) Plasma membrane: It is a thin membrane which controls the passage of materials in and out of the cell. It is also called as selectively permeable membrane. It makes the outer boundary of the cell and is made up of lipo-protein.

(b) Cytoplasm: It is transparent jelly-like thick substance present in the cell. It makes the ground of the cell in which all the cell organelles are suspended.

(c) Nucleus: It is a double-layered membrane structure which contains chromosomes required for the inheritance of characteristics from one generation to the other.

Value Based Questions

1) Sanjay was helping his mother in laying the table when they had some guest for dinner. Sanjay was about to sprinkle salt on salad for dressing. His mother stopped him from doing so and told him that it is too early to sprinkle salt on the salad, he should do so only when they are seated for having the dinner.

(a) What would happen if salt is sprinkled on the salad?

(b) Which property of cells is seen in adding salt to it?

(c) What value of Vasu is seen?

Answer:

(a) On sprinkling of some salt on the salad, the salad will release water.

(b) The salt outside the salad acts as hypertonic solution as it has less water concentration and therefore the cell looses water by osmosis.

(c) Sanjay showed the value of being very helpful, caring and responsible.

2) Srinidhi is a five year old girl who joined the swimming classes. After the first class she was worried when she saw her wrinkled fingers. She asked her elder sister about the wrinkling and shrinking of her fingers. Her sister explained Srinidhi why it was so.

(a) Why did the fingers wrinkle after swimming?

(b) What caused the shrinking/wrinkling of fingers?

(c) What value of Srinidhi is seen in the above cast?

Answer:

(a) Fingers wrinkled because the cells of the skin lost some water.

(b) This happened because of the difference in the concentration of water in the skin cells and swimming pool’s water.

(c) Srinidhi showed the value of aware citizen and a good learner who clarifies the doubts.

NCERT Solutions for Class 9 Science Chapter 4 – Structure of the Atom
1)What are canal rays?

Soln:

Canal rays are radiations which are positively charged and was the key in the discovery of proton, another positively charged subatomic particle.

2)  If an atom contains one electron and one proton, will it carry any charge or not?

Soln:

Since an electron is a negatively charged particle and the proton, a positively charged one, the net charge becomes neutral as both the particle neutralises each other.

3) On the basis of Thompson’s model of an atom, explain how the atom is neutral as a whole.

Soln: According to the Thompson’s model,

(i) An atom contains a positively charged sphere in which the negatively charged electrons are embedded.

(ii) In the system the number of protons and the electrons are equals therefore neutralising their charge keeping the overall system neutral.

4) On the basis of Rutherford’s model of an atom, which subatomic particle is present in the nucleus of an atom?

Soln: According to the Rutherford’s model of an atom, the positively charged protons are the ones that are present in the atom.

5) Draw a sketch of Bohr’s model of an atom with three shells.

Soln:

6) What do you think would be the observation if the – particle scattering experiment is carried out using a foil of a metal other than gold?

Soln:

When in the – particle scattering experiment, when any other metal foil is used instead of gold, the observation would remain the same. This is because the structure of an atom when considered individually remains the same.

7) Name the three subatomic particles of an atom.

Soln: An atom consists of three subatomic particles:

• Protons which are positively charged
• Electrons which are negatively charged
• Neutrons which are neutral in nature ( no charge )

8) Helium atom has an atomic mass of 4 u and two protons in its nucleus. How many neutrons does it have?

Soln:

Atomic mass = number of (protons + neutrons)

4= 2 + number of neutrons

Number of neutrons = 4 – 2 = 2

Therefore, Helium has 2 neutrons.

9) Write the distribution of electrons in Carbon and Sodium atoms.

Soln:

Carbon atom: Atomic number = 6

Number of protons = 6 = Number of electrons

Distribution = K-2 ; L-4

Sodium atom: Atomic number = 11

Number of protons = 11 = Number of electrons

Distribution = K-2 ; L-8 ; M-1

10) If K and L shells of a n atom are full, then what would be the total number of electrons in the atom?

Soln:

Number of electrons K shell can hold = 2

Number of electrons L shell can hold = 8

Hence, when both the shells are full, the total number of electrons present = 2+8 = 10 electrons.

11) How will you find the valency of Chlorine, Sulphur and Magnesium?

Soln:

The valency of an element is defined as its combining power with other atoms when it forms chemical compounds or molecule. It is measured by finding the number of electrons needed to complete the shell in which it is present or the excess electrons present after the filling is complete.

Chlorine: Atomic number = 17

Number of protons = Number of electrons = 17

Distribution: K-2 ; L-8 ; M-7

From the above observation, it is noticed that one more electron is required to fill the M shell. Hence its valency is ( -1 ) that is it is one electron less.

Sulphur: Atomic number = 16

Number of protons = Number of electrons = 16

Distribution: K-2 ; L-8 ; M-6

From the above observation. It is noticed that two more electrons are required to fill the M shell. Hence its valency is ( -2 ) that is it is two electrons less.

Magnesium: Atomic number = 12

Number of protons = Number of electrons = 12

Distribution: K-2 ; L-8 ; M-2

From the above observation, it is noticed that 6 more electrons are required to complete the M shell. However, M shell has only two electrons, it has less electrons than it requires to complete the arrangement. Therefore, this atom is unstable because of the presence of two electrons in the M shell. Therefore, its valency is ( +2 ) that is it is excess of two electrons.

12) If the number of electrons in an atom is 8 and number of protons is also 8, then

(a) What is the atomic number of the atom?

(b) What is the charge on the atom?

Soln:

Given: Number of electrons = 8

Number of protons = 8

(a) Atomic number of the atom = Number of protons = 8

(b) As the number of electrons is equal to the number of protons on the atom, their charges neutralise each other. Therefore, the atom does not possess any charge.

13) With the help of given Table, find out the mass number of Oxygen and Sulphur atom.

Table: Composition of Atoms of the First Eighteen Elements with Electron Distribution in Various Shells.

(a)

(b)

Soln:

(a) Oxygen: Number of protons = 8

Number of neutrons = 8

Atomic number = 8

Atomic mass number = Number of ( protons + neutrons )

= 8 + 8 = 16

(b) Sulphur: Number of protons = 16

Number of neutrons = 16

Atomic number = 16

Atomic mass number = Number of ( protons + neutrons )

= 16 + 16 = 32

14) For the symbol H, D and T, tabulate three subatomic particles found in each of them.

Soln:

(a) H ( Protium ) (11H)

Atomic number = 1

Mass number = 1

Number of protons = 1

Number of electrons = 1

Number of neutrons = Nil

(b) D ( Deuterium )   ( 21H )

Atomic number = 1

Mass number = 2

Number of protons = 1

Number of electrons = 1

Number of neutrons = 1

(c) T ( Tritium )  ( 31H )

Atomic number = 1

Mass number = 3

Number of protons = 1

Number of electrons = 1

Number of neutrons = 2

15) Write the electronic configuration of any one pair of isotopes and isobar.

Soln:

(a) Isotopes: Isotopes are atoms which has the same number of protons but the number of neutrons differs. This leads to the variation in mass number too.

Example: The most simple example is the Carbon molecule which exists as ₆C¹² and ₆C¹⁴ but when their electronic configuration is noticed, both have K-2 ; L-4

(b) Isobars: Isobars are atoms which has the same mass number but differ in the atomic number. Electronic configuration of an isobar pair is as follows,

₂₀Ca⁴⁰ :- K-2 ; L-8 ; M-8 ; N- 2

₁₈Ar⁴⁰ :- K-2 ; L-8 ; M-8

Exercises:

(1) Compare the properties of electrons, protons and neutrons.

Soln:

2)  What are the limitations of J.J.Thomson’s model of the atom?

Soln:

• The model of an atom proposed by J.J Thomson states that in a positive sphere, are the negatively charged electrons embedded
• But he did not have any experimental evidence in his support.
• Also, the model was not able to explain the scattering of light experiment done by Rutherford.

3) What are the limitations of Rutherford’s model of the atom?

Soln: In the model that he suggested for atom, Rutherford states that the electrons revolve around the nucleus of an atom in the same way the earth revolves around the sun.

But, whenever this situation prevails, the revolving particle gains acceleration and radiates its energy outwards. With continuous radiation of energy, the atom would lose its energy and fall into the nucleus which when happens makes the atom highly unstable. But on the contrary, we find the atom as a highly stable particle which disproves the assumption.

4) Describe Bohr’s model of the atom.

Soln:

• The nucleus of an atom is present in the centre.
• Around this nucleus will revolve the negatively charged electrons.
• Discrete orbits of electrons are present inside the atom.
• While in this orbits, the electrons do not radiate energy.
• These discrete orbits are represented as K, L, M, N orbits or denoted with the numbers n=1, 2, 3, 4

5) Compare all the proposed models of an atom given in this chapter.

Soln:

6) Summarise the rules for writing of distribution of electrons in various shells for the first eighteen elements.

Soln:

• Generally, the maximum number of electrons that can be accommodated in a shell is given by the formula: 2n² , where n= 1, 2, 3…
• Maximum number of electrons in different shells are:

K shell – n=1 ; 2n² = 2(1)² = 2

L shell – n=2 ; 2n² = 2(2)² = 8

M shell – n=3 ; 2n² = 2(3)² = 18

N shell- n=4 ; 2n² = 2(4)² = 32

• Given number of electrons is 18.
• The electrons are not taken in unless the inner shells are filled.
• Hence the highest element has K-2 ; L-8 ; M-8.

7) Define valency by taking examples of silicon and oxygen.

Soln:

The valency of an element is defined as its combining power with other atoms when it forms chemical compounds or molecule. It is measured by finding the number of electrons needed to complete the shell in which it is present or the excess electrons present after the filling is complete.

For example, take the example of silicon and oxygen.

8) Explain with examples;

(a) Atomic number

(b) Mass number

(c) Isotopes

(d) Isobars

Give any two uses of isotopes.

Soln:

(a) Atomic number of an atom is defined as the number of positively charged protons present in the atom nucleus. Example: Hydrogen has one proton in its nucleus, hence its atomic number is one.

(b) Mass number of an atom is defined as the total number of protons as well as neutrons. The take into account the elements that contribute to the atomic mass of the atom, since the mass of electrons are negligible as compared to the protons and neutrons of the corresponding element.

(c) Isotopes: Isotopes are atoms which has the same number of protons but the number of neutrons differs. This leads to the variation in mass number too.

Example: The most simple example is the Carbon molecule which exists as ₆C¹² and ₆C¹⁴

(d) Isobars: Isobars are atoms which has the same mass number but differ in the atomic number. Examples are, ₂₀Ca⁴⁰ and  ₁₈Ar⁴⁰

Uses of isotopes:

• The isotope of Iodine atom is used to treat goitre, and iodine deficient disease.
• Fuel for nuclear reactors are take care with the isotopes of Uranium atom.

9) Na⁺ has completely filled K and L shells. Explain.

Soln:

A sodium atom has 11 electrons in its orbitals, since its atomic number is 11 and has the same number of protons and electrons. Thus its electronic configuration is K-2 ; L-8 ; M-1 ; The one electron in the M shell is lost and it obtains a positive charge since it has one more proton than the electrons, and obtains a positive charge, Na⁺ . Now the configuration is K-1 ; L-8 which is the filled state. Hence it is very difficult to remove the electron form a filled state as it is very stable.

10) If Bromine atom is available in the form of say, two isotopes  ₃₅Br⁷⁹ (49.7%) and ₃₅Br⁸¹ (50.3%), calculate the average atomic mass of Bromine atom.

Soln:

The atomic masses of two isotopic atoms are 79 (49.7%) and 81 (50.3%).

Thus, total mass = (79 * 49.7100 ) + (81 * 50.3100)

= 39.263 + 40.743

= 80.006 u

11) The average atomic mass of a sample of an element X is 16.2 u. What are the percentages of isotopes ¹⁶₈X and ¹⁸₈X in the sample?

Soln:

Let the percentage of ¹⁶₈X be ‘p’ and that of ¹⁸₈X be ‘100-p’.

Hence, (16 * p100 ) + (18 * 100−p100)

= 16.2

= 16p100 + 1800−18p100

= 16.2

On solving the equation, we obtain ‘p’ to be 90.

Therefore, ¹⁶₈X = 90%

And , ¹⁸₈X = 10%

12) If Z=3, what would be the valency of the element? Also, name the element.

Soln:

Z = atomic number = 3 (given)

Electronic configuration = K-2 ; L-1

Thus, valency = 1

The element with atomic number 3 is Lithium.

13) Composition of the nuclei of two atomic species X and Y are given as under X-Y

Protons = 6-6

Neutrons = 6-8

Give the mass number of X and Y. What is the relation between the two species?

Soln:

Mass number of X: 6+6 = 12

Mass number of Y: 6+8 = 14

Since the atomic numbers of both the species are the same, they are the same element. Also since they have different number of neutrons, their mass number is different and they are the isotopes.

14) For the following statements, write T for true and f for false.

(a) J. Thomson proposed that the nucleus of an atom contains only nucleons.

(b) A neutron is formed by an electron and a proton combining together. Therefore it is neutral.

(c) The mass of an electron is about 1/2000 times that of proton.

(d) An isotope of iodine is used for making tincture iodine, which is used as a medicine.

Soln:

(a) False

(b) False

(c) True

(d) false

Put tick against correct choice and cross against wrong choice in questions 15, 16 and 17.

15) Rutherford’s alpha – particle scattering experiment was responsible for the discovery of

(a) Atomic nucleus

(b) Proton

(c) Electron

(d) neutron

Soln:

(a) Atomic nucleus

16) Isotopes of an element have

(a) The same physical properties

(b) Different number of neutrons

(c) Different number of protons

(d) Different atomic number

Soln:

(b) different number of neutrons

17) Number of valence electrons in Cl^– ion are:

(a) 16

(b) 8

(c) 17

(d) 18

Soln:

(b) 8

18) Which one of the following is a correct electronic configuration of Sodium?

(a) 2, 8

(b) 8, 2, 1

(c) 2, 1, 8

(d) 2, 8, 1

Soln:

(d) 2, 8, 1

19) Complete the following table

Soln:

General Question: Illustrate the relationship between a mole, Avogadro’s number and Mass.

Q1. A reaction is taking place wherein, 5g of sodium carbonate reacts with 7.2 gm of ethanoic acid. The products are 4.2g carbon dioxide, 3g water and 5g sodium ethanoate. Prove how these observations are in coherence with the law of mass conservation.

Ans.

Sodium carbonate + ethanoic acid water+ carbon dioxide +  Sodium ethanoate

5g                                7.2g                    3g             4.2g                       5g

LHS    = RHS

12.2g = 12.2g

This observation thus shows that during a chemical reaction, mass of reactant = mass of product.

Q2.Hydrogen reacts with oxygen in the ratio 1:8 by mass to form water. How much oxygen is required to completely react with 4g of hydrogen?

Ans.

We know hydrogen and water mix in the ratio 1: 8.

Thus, 1: 8 = 4: x           (where x is the amount of oxygen)

x      =8 * 4

= 32g

Therefore, 32g of oxygen would be required to completed react with 4g of hydrogen.

Q3. Which postulate of Dalton’s Atomic theory is the result of the law of conservation of mass?

Ans.

The postulate of Dalton’s Atomic theory which is a result of the law of conservation of mass is, “Atoms can neither be created nor destroyed”.

Q4. Which postulate of Dalton’s Atomic theory can explain the law of definite proportions?

Ans.

The postulate which can explain the law of definite proportions is that the relative number and the kinds of atoms are constant in a given compound.

Q5. What is an atomic mass unit?

Ans.

An atomic mass unit is a unit of mass used to express weights of atoms and molecules where one atomic mass is equal to 1/12^th the mass of one carbon-12 atom.

Q6. Why aren’t atoms visible to a naked eye?

Ans.

Firstly, atoms are very very minute, measuring in nanometers. Secondly, except for atoms of noble gasses, they do not exist independently. For these basic reasons, we cannot see an atom with our naked eye.

Q7.Write the formulae for the following:

• Carbon dioxide
• Calcium hydroxide
• Ammonium chloride
• Aluminum chloride

Ans.

Carbon dioxide-CO₂, Calcium hydroxide- Ca(OH)_2, Ammonium Chloride – NH₄CL, Aluminum Chloride – AlCl₃

Q8.What does chemical formula mean?

Ans.

The symbolic representation of a chemical compound is called its chemical formulae. E.g. chemical formulae of salt is NaCl.

Q9. Find the number of atoms the following possess: – (i)H₂O molecule (ii)H₂S molecule

Ans.

H₂O3 atoms present

H₂S  3 atoms present.

Q10.Find out the molecular masses ofCO₂, O_2, H_2, CL₂, NH₃, C₂ H₂, CH₃ OH.

Ans. 

H₂ = 1 x 2 = 2u

O₂= 16 x 2 =32U

CO₂=1 x 12 + 2 x 16 =44U

CL₂= 35.5 x 2= 71u

NH₃ = 1 x 14 + 3 x 1 =17u

C₂H₂ = 2 x 12 + 2 x 1 =26u
CH₃OH =12 + 3 x 1 + 16 + 1 = 32u

Q11.Work out the formula unit masses of K₂CO₃, ZnO, Na₂O.

(Atomic masses of Zn=65u, Na= 23u, K=39u, C=12u and O= 16u)

Ans.

ZnO= 65u + 16u = 81u

Na₂O= (23u x 2) + 16u = 46u + 16u = 62u

K₂CO₃ = (39u x 2) + 12u + 16u x 3=138u

Q12. What is the mass of 1 carbon atom, if one mole of carbon atoms weigh 12gm?

Ans.

1 mole of carbon atoms, 6.022 x 10²³ = 12g

Therefore, mass of 1 carbon atom = 12/6.022 x 10²³

= 1.99 x 10^-23g

Q13.Out of 100g of sodium and 100g of iron which one is heavier?

(Atomic mass of Na=23u, Fe= 56u)

6. 23g of Na = 6.022 x 10²³atoms

100g   Na  = x10²³ = 2.6182 x 10²⁴atoms

56g of Fe  = 6.022 x 10²³ atoms

100g of Fe=100 x (6.022/56) x 10²³= 1.057 x 10²⁴atoms

Thus, it is evident from the above calculations that 100g of Na has more atoms.

Q14. A 0.20g compound of oxygen and boron was found to contain 0.080g of boron and 0.12.Calculate the percentage composition of the compound by weight.

Ans.

Compound Boron + Oxygen 

0.20               0.080      0.12

Percentage composition of boron:

0.20g 0.040g

100 x (0.080/0.20)=40%

Percentage composition of oxygen:

100 x (0.12/0.20)= 60%

Q15. 3g of carbon is burnt in 8g of oxygen, 11g of carbon dioxide is the by-product. What mass of CO₂ is formed when 3g of carbon is burnt in 40g of oxygen?  Which law of chemical combination does the answer follow?

Ans.

The chemical reaction of carbon burning in oxygen is:

C          +          O         CO2

1 mole             1 mole         44g

12g                 32g

It is given that 3g of carbon requires 8g gram of oxygen to produce 11g of carbon-dioxide. Thus when 3g of carbon burns in 40g of oxygen, we still get 11g of carbon dioxide with 40-8= 32g of oxygen remaining. The answer follows the law of constant proportion.

Q16.What do you understand by polyatomic ions?

Ans.

Polyatomic ions are ions that contain more than one atom but they behave as a single unit e.g. CO₃ ^2- , H₂PO₄^–.

Q17. What is the chemical formula of the following compounds?

Methane

Vinegar, Sodium Thiosulphate

 Calcium Carbonate

Potassium Hydroxide

 Magnesium chloride.

Ans.

Methane- CH₄

Vinegar –CH₃COOH

Sodium Thiosulphate – Na₂S₂O₃.5H₂O

Calcium Carbonate – CaCO₃

Potassium Hydroxide – KOH

Magnesium Chloride –MgCl₂

Q18. What are the names of the elements present in the following compounds:

Potash Alum, Quick lime, Plaster of Paris, Common Salt and Baking powder

Ans.

Potash alum – Potassium Aluminum Sulphate

Elements –Potassium,   Aluminum, Sulphur, Oxygen and Hydrogen

Quick lime     – Calcium oxide

Elements- Calcium and oxygen

Plaster of Paris – Calcium Sulphate

Elements – Calcium, Sulphur, Oxygen and Hydrogen

Common Salt   – Sodium Chloride

Elements –Sodium and chlorine

Baking Powder – Sodium Hydrogen Carbonate

Elements- Sodium, Hydrogen, Carbon and Oxygen.

Q19. Find the molar mass of the following compounds:

Hydrochloric Acid (Hcl)

Ammonia(NH₃)

 Nitric Acid (HNO₃)

 Acetic Acid (CH₃COOH)

Acetone(C₃H₆O)

Ans.

HCL = 1 + 35.5 = 36.5g

NH3= 14 + 1 x 3 =17g

HNO3 = 1 + 14 + 16 x 3 = 63g

CH3COOH = 12 + 3 x 1 + 12 + 16 x 2  + 1 =60g

C3H6O = 12 x 3 + 6 x 1 + 16 = 58g

Q20. Find the mass of:

• 1 mole of oxygen
• 5 moles of chlorine atoms
• 10 moles of ammonia

 Ans.

1 mole of oxygen = 16g

5 mole of chlorine atoms = 5 x 35.5= 177.5g

1 mole of ammonia(NH₃) = 14 + 3 x 1 =17g

Thus, 10 moles of ammonia = 10 x 17 = 170g.

Q21. Convert the given mass into mole:

1. 10g of chlorine gas.
2. 12g of Carbon dioxide.
3. 10 gram of oxygen gas.

 Ans.

a) Given mass of chlorine gas = 10g.

Molar mass of chlorine gas = 71g.

Thus, mole of 10g of chlorine gas = 10/71=0.1408 moles.

b) Given mass of CO₂ = 12g.

Molar mass of CO₂ = 12 + 16 x 2 =44g.

Thus, mole 12g of CO₂ = 12/44 =0.272 moles.

c) Given mass of O₂ =10g.

Molar mass of O₂ = 16 x 2 =32g.

Thus,  mole of 10g of O₂ = 10/32 =0.3125 moles.

Q22. Find the mass of:

a) 2 moles of water molecules.

b) 5 moles of carbon dioxide molecules.

 Ans.

a) Mole of water molecules = 0.2

Molar mass of H₂O =1 x 2 + 16 =18g

Mass of 0.2 moles of H₂O =18 x 0.2 =3.6g

b) Mole of CO₂ molecule = 0.5.

Molar mass of CO₂ =12 + 16 x 2 =44g.

Mass of 0.5 moles of CO₂ = 0.5 x 44 =22g.

Q23. What is the number of molecules of Sulphur (S₈) present in 32g of solid sulphur?

Ans.

Molar mass of sulfur = 256g = 6.022 x 10²³molecule

Given mass of sulfur = 32g

Therefore, the number of molecules =  * 10²³

=7.75 x 10²²molecules.

Q24.Find the number of aluminum ions present in 0.046g of aluminum oxide. (For an   element, the mass of its ion and  atom  are the same)

Ans.

Molar mass of aluminum oxide, Al2O3 = (2 x 27) + (3 x 16) = 102g

Now,

102g of Al₂O₃ contains = 2 x 6.022 x 10²³ aluminum ions

Therefore,

0.046 g Al₂O₃ contains = * 10²³

= 5.432 x 10²⁰ Al³⁺ ions.

Q25. Multiple choice questions:

Choose the option:

1. The atomicity H₂SO₄ is:

(a)12    (b)7

(c)19   (d)8

2. The chemical formula for  acetic acid is:

 (a)CH₃COOH   (b)CaCl₂

(c)CaO             (d)CaCO₃

3. The symbol for gold is:

(a)Cd               (b)Hg

(c)Gd               (d)Au

4. Noble gas molecules have:

(a) diatomic    (b)triatomic

(c) monoatomic (d)none of the above

5. The valency of oxygen in a water molecule is:

(a)1                 (b)2

(c)3                 (d)5

6. The molar mass of Ethyne, C₂H₂ is:

(a) 26g             (b) 21g

(c) 25g             (d) 15g           

7. How many moles of oxygen are present in 3.2g of oxygen atoms?

(a) 0.2moles                (b) 0.9 moles

(c) 1.2 moles               (d) 1 moles.

8.Which among the following is not proposed by Dalton in his atomic theory?

(a) Atoms cannot be divided further

 (b)Only atoms of the same elements can combine to form compounds.

(c) Atoms of different elements have different sizes, masses and chemical properties.

(d) Atoms can neither be created nor destroyed.

9.Pick the wrong one out:

(a) 1 mole of hydrogen = 1g

(b)1 mole of oxygen      = 32g

(c) 1 mole of Carbon       =18g

(d)1 mole of chlorine = 35.5g

 10. From the following compounds which one has a molecular mass of 106.

(a) Na₂CO₃      (b)H₂SO₄

(c)CaCl            (d)none of the above

Ans. 1-(b) , 2- (a) , 3- (d) , 4 –(c) , 5- (b) , 6- (a), 7 –(a) , 8 – (b) ,9- (c) , 10- (a). 

Q26.State the law of mass conservation.

Ans.

According to this law, mass can neither be created nor destroyed in a chemical reaction or a physical transformation.

Q27.What do you understand by the law of constant proportion?

Ans.

According to the Law of constant proportion, a chemical compound always has its compounding elements in definite proportion by mass, irrespective of the source and the type of chemical reaction.

Q28.Who was responsible for coining the term atom?

Ans.

In modern science, John Dalton widely used it and he can be said to be responsible for coining it, but a more factually correct answer would be a Greek philosopher who goes by the name of Lucretius.

Q29.Define atom.

Ans.

Atom is the smallest particle of matter which can take part in a chemical reaction.

Q30.What is a molecule?

Ans.

A molecule is a group of atoms bonded together which represents the most fundamental unit of a chemical compound capable of taking part in a chemical reaction.

Q31.What is atomicity?

Ans.

Atomicity is the number of atoms in a molecule.

Q32.Define atomic mass unit.

Ans.

The Atomic mass unit is the sum of the atomic masses of all the atoms in a molecule.

Q32.What is the atomicity of oxygen and phosphorous?

Ans.

Atomicity of oxygen, O2= 2 and atomicity of phosphorous, P4= 4.

Q33. Define ion.

Ans.

An ion is an atom or a molecule with an electric charge (+ve or -ve), caused by gain or loss of a single or multiple electrons.

Q34. Provide a difference between cations and anions, along with an example for each.

Ans.

Cations are positively charged ions, e.g.  Fe²⁺ whereas, anions are negatively charged ions, e.g. F^–

Q35.Define Avogadro’s constant.

Ans.

Avogadro’s Constant (6.022 x 10²³) is the number of atoms of an element present in one mole of that element.

Q36.Calculate the molecular mass of glucose, C ₆H₁₂ O_6.

Ans.

Molecular mass of C₆H₁₂ O₆ = (12 x 6) + 12 + (16 x 6)

= 180u.

Q37.What is the unit to measure the size of an atom, and what is the size of a hydrogen atom?

Ans.

An atom’s size is measured in nanometers and a hydrogen atom is 0.1 nm.

Q38. What does IUPAC stand for? State any one of its roles.

Ans.

IUPAC stands for the International Union of Pure and Applied Chemistry. One of its roles is to approve the naming of elements

Q39. What is the Latin name for the following elements: gold, silver, sodium, potassium?

Ans.

Gold – Aurum, Silver- Argentum, Sodium – Natrium, Potassium – Kalium.

Q40. What is the ratio by mass of the constituent elements in CO₂, NH₃ and H₂O?

Ans.

CO2 by mass of combining elements 12:32 3:8 (C:O)

NH3 by mass of combining elements  14:314:3 (N:H)

H2O by mass of combining elements   2:16  1:8 (H:O)

Q41.What is valency? Give the valency of the following elements:  beryllium, neon, magnesium, hydrogen, chlorine.

Ans.

Valency is the number of electrons an atom can use to combine with other atoms or in other words, it is the combining power of an atom.

Beryllium-2, neon-0, magnesium-2, hydrogen-1, chlorine-2.

Q42.What is a polyatomic ion?

Ans.

Polyatomic ions are composed of two or more atoms acting as a single unit. E.g. NH₄⁺

Q43.What are the chemical formulae for: Acetone, copper nitrate and aluminum hydroxide.

Ans.

Acetone- (CH₃)₂CO

Copper Nitrate-  Cu(NO₃)

Aluminum Hydroxide – Al(OH)₃

Q44.Calculate the number of moles in:

(i)36g of H₂O

(ii)69g of Na

Ans.

(i) Molar mass of H2O=2 x 1 + 16 =18g

Given mass of H2O =36g

Therefore, number of moles in 36g of H2O = 36/18 =2 moles

(ii) Molar mass of Na = 23g

Given mass of Na =69g

Therefore, number of moles in 69g of Na = 69/23 =3 moles.

Q45.What are the rules for writing the symbol of an element?

Ans.

Firstly, the symbol has to be IUPAC approved.

The symbols are the first one or two letters of that element in English, Latin, German or Greek. E.g. He for helium, O₂ for oxygen.

And, the first letter of the symbol has to be in upper case and the second letter has to be in lower case e.g. Na , Cl, etc.

Q46. What do you understand from relative atomic and relative molecular mass?

Ans.Relative atomic mass is the ratio of the mass of one atom to the 1/12^th mass of a carbon-12 atom.

Relative molecular mass is the ratio of the mass of one molecule of an element to 1/12^th of the mass of a carbon-12 atom.

Q47. H₂O is the formula for water. What information do you get from this formula?

Ans.

• H₂O represents water
• H₂O is a single molecule of water
• H₂O is a single mole of water. Thus, it contains 6.022 x 10²³ molecules of water.
• H₂O contains 2 atoms of hydrogen and 1 atom of oxygen.
• H₂O has a molar mass of 18g

Q48.Differentiate between an atom and an Ion.

Ans.

Q48.What is the formula unit mass of CaCl₂ and NaCl.

(Na = 23, Cl=35.5, Ca=40)

Ans.

Formula Unit Mass of NaCl = 23 + 35.5 = 58.5u

Formula Unit Mass of CaCl₂= 40+(2 x 35.5)= 111u.

Q49. The ratio by mass of hydrogen to oxygen in a water molecule is 1: 8. Calculate the ratio of the number of atoms in a water molecule.

Ans.

Thus, the ratio of the number of atoms in a water molecule is  H: O = 2: 1.

Q50. Write the chemical formula for the following compounds:

(a) Zinc carbonate

(b) Copper phosphate

(c) Aluminum carbonate

(d) Aluminum hydroxide

(e) Magnesium bicarbonate

(f) Calcium sulphide

Ans. 

(a)Zinc             Carbonate

Zn²⁺             CO₃^2-

Formula = ZnCO₃

(b)Copper        Phosphate

           Cu²⁺                                     PO₄^3-

Formula = Cu₃(PO₄)₂

(c)Aluminum         Carbonate

Al³⁺                                                           CO₃^2-

                   Formula= Al₂(CO₃)₃

(d)Aluminum            Hydroxide

Al³⁺                                     OH^–

                                    Formula =  Al(OH)₃

(e)Magnesium           Bicarbonate

Mg²⁺                                HCO₃^–

                                    Formula = Mg(HCO₃)₂

(f)Calcium                         Sulphide

Ca²⁺                                     S^2-

   Formula = CaS

Q51.Write the atomicity of the following compounds:

1. Al₂(SO₄)₃
2. Mg(HCO₃)₂
3. ZnCO₃
4. HCL
5. H₂O
6. H₂SO₄

Ans.

1. Al₂(SO₄)₃ = 17
2. Mg(HCO₃)₂ = 11
3. ZnCO₃ = 5
4. HCL=2
5. H₂O = 3
6. H₂SO₄=7

Q52. What is the difference between  2O, O₂ and O₃.

Ans.

2O represents 2 atoms of oxygen, and it is not possible for it to exist independently.

O₂ represents an oxygen molecule which has two constituent oxygen atoms.

O₃ represents a single ozone molecule and it does exist independently.

Q53. (a)Explain how atoms exist.

          (b)What do you understand by atomicity?

          (c) Explain polyatomic ions.

Ans.

(a) Atoms of most elements don’t exist independently they exist as molecules, for molecules are more stable. However, atoms of inert gasses are chemically unreactive and they exist independently. E.g. helium.

(b) Atomicity is the number of atoms in a molecule. E.g. The atomicity of H2O = 3.

(c) A polyatomic ion is an ion composed of multiple atoms acting as a single charged unit.

Q54. Find out

(1) the mass of a single oxygen atom

(2) the mass of a single oxygen molecule

 (3) the mass of a mole of oxygen gas

(4) the mass of an oxygen ion

(5) the number of atoms in a mole of an oxygen molecule.

Ans.

(1) Mass of a single oxygen atom

1 mole of oxygen atom = 16gm =6.022 x 10²³ atoms

Therefore, Mass of one oxygen atom = 16/6.022 x 10²³ = 2.65 x 10^-23 gm

(2) Mass of a single oxygen atom

1 molecule oxygen = O₂ =2 x 16 = 32u

(3) Mass of a mole of oxygen gas

1 mole of oxygen = O₂ = 2 x 16 =32u

(4) Mass of an oxygen ion = mass of an oxygen atom (since electrons have negligible mass)

(5) Number of atoms in a mole of oxygen molecule

We know, 1 mole of oxygen molecule, O₂ = 6.022 x 10²³ molecules.

1 molecule of O₂= 2 atoms

Therefore in a mole of O₂ , there are                       =6.022 x 10²³ x 2 atoms

= 1.022 x 10²⁴ atoms.

Q55. Explain atomic mass and gram atomic mass. Why does mass have different expressions viz,   ‘u’ and ‘gm’?

Ans.

Atomic mass is the unit in which the mass of an atom is expressed, where one atomic mass unit is 1/12^ththe mass of a carbon-12 atom.

Gram atomic mass is the atomic mass of an element expressed in grams.

The mass of an atom or a molecule is expressed in ‘u’, whereas, the molar mass is expressed in ‘gm’.

Q56. Define a mole. Give the importance of the mole.

Ans.

One mole of atoms, molecules, or particles is that amount of the particle(atoms, molecules and ions) whose mass is equal to that particle’s atomic or molecular mass in grams. 1 mole = 6.022 x 10²³ particles of that substance.

Importance of a mole:-

• Atoms and molecules are very small. So it gets bothersome weighing them in grams and trying to count them. Mole concept, however, allows us to count atoms and molecules by weighing macroscopic amounts of materials.
• It gives us a universally accepted standard of mass.
• It provides a standard for reaction stoichiometry.

Q57. A gold ring has 90% gold and 10% copper.

(a) How many atoms are there in a gram of gold

(b) What is the ratio of gold to copper in this jewelry?

 Ans.

(a) 1 gram of gold contains 90/100 = 0.9 grams of gold

Now, number of moles of gold  = Mass of gold/Atomic mass of gold

= 0.9/197 =0.0046

Therefore,0.0046 moles of gold will contain= 0.0046 x 6.022 x 10²³

                                                                                                                                                   = 2.77 X 10²¹ atoms.

(b)Ratio of gold : copper = 9 : 1