Questions Answers

Evaluation

I. Choose the appropriate answer

1. When ice melts to form water, change occurs in its

a. position

b. colour

c. state

d. composition

Answer: c. state

2. Drying of wet clothes in air is an example of

a. Chemical change

b. Undesirable change

c. irreversible change

d. physical change

Answer: d. physical change

3. Formation of curd from milk is

a. a reversible change

b. a fast change

c. an irreversible change

d. an undesirable change

Answer: c. an irreversible change 

4. Out of the following an example of a desirable change is

a.Rusting

b.change of seasons

c.earthquake

d. flooding

Answer: b. change of seasons

5. Air pollution leading to Acid rain is a

a. reversible change

b. fast change

c. natural change

d. human made change

Answer: d. human made change

II. Fill in the blanks

1. Magnet attracts iron needle. This is a reversible change. (a reversible / an  irreversible)

2. Boiling of egg results in an irreversible  change. (a reversible / an irreversible)

3. Changes that are harmful to us are undesirable (desirable / undesirable)

4. Plants convert Carbon-di-oxide and water into starch. This is an example of natural change. (natural / human made)

5. Bursting of fire crackers is a fast change whereas germination of seeds is a slow change. (slow / fast)

III. True or False. If False, give the correct statement

1. Growing of teeth in an infant is slow change. [True]

2. Burning of match stick is a reversible change. [False]

The match stick undergoes a chemical change. It is an irreversible change.

3. Change of New moon to Full moon is human made. [False]

Change of New moon to Full moon is a natural change.

4. Digestion of food is a physical change. [False]

The digested food undergoes chemical change.

5. In a solution of salt in water, water is the solute [False]

In a solution of salt in water, water is a solvent.

IV. Analogy

1. Curdling of milk : irreversible change :: Formation of clouds : reversible change

2.  Photosynthesis : natural change :: burning of coal : Human – made change

3. Dissolving of glucose : reversible       change :: Digestion of food: irreversible change

4. Cooking of food : desirable change :: decaying of food : undesirable change

5. Burning of matchstick : Fast change: Rotation of the Earth : Slow change

V. Circle the odd one out. Give reason for your choice

1. Growth of a child, Blinking of eye, Rusting, Germination of a seed

Growth of a child, (Blinking of eye), Rusting, Germination of a seed

Blinking of eye is a fast change. Others are slow changes.

2. Glowing of a bulb, lighting of a Candle, breaking of a coffee mug, curdling of milk

Glowing of a bulb, lighting of a Candle, breaking of a coffee mug, (curdling of milk)

Curdling of milk is a slow change. Others are fast changes.

3. Rotting of an egg, condensation of water vapour, trimming of hair, Ripening of fruit

Rotting of an egg, condensation of water vapour, (trimming of hair,) Ripening of fruit

Trimming of hair is a fast change. Others are slow changes.

VI. Give very short answer

1. What kind of a change is associated with decaying of a plants?

Natural change, irreversible change, slow change.

2. You are given some candle wax. Can you make a candle doll from it? What kind of change is this?

Yes, it is a human-made change.

3. Define a slow change.

Changes which take place over a long period of time are known as slow changes.

4. What happens when cane sugar is strongly heated? Mention any two changes in it.

When cane sugar is strongly heated the water in it becomes steam and it physical change. Finally the sugar undergoes chemical change and only carbon remains in the dish.

5. What is a solution?

The spreading of the solid particles (broken into individual molecules) among the liquid molecules is called as dissolution.

VII. Give short answer

1. What happen when paper is burnt? Explain.

When paper is burnt it undergoes chemical change. It is a fast change, irreversible change and human made change. 

2. Can deforestation be considered a desirable change? Explain.

No, deforestation is an undesirable change. Forests provide shelter to millions of animals and insects. We get rain due to forests. The trees in the forest purify the air by absorbing carbon dioxide and releasing oxygen. They give us food, fruit, medicine, furniture and fuel. The earth is green because of trees and plants. So deforestation is an undesirable change.

3. What type of changes is associated with germination of a seed? Explain

The germination of a seed is a natural change. It is a slow change because the seed takes considerable time to grow into a sapling. It is an irreversible change and it is a desirable change as well.

VIII. Answer in detail

1. Give one example in each case that happens around you.

a. Slow and fast change

Slow change: The colour of wall paint in our school becomes dim in due course.

Fast change: A beaker dropped accidentally breaks to pieces.

b. Reversible and irreversible change

Reversible change: A spring elongates when pulled slightly. It reaches its former position when we stop pulling it.

Irreversible change: The chemical change in a burnt match stick.

c. Physical and chemical change

Physical change : Water kept in a refrigerator becomes ice.

Chemical change: The iron bars in our classroom windows become rusted.

d. Natural and man-made change

Natural change: A sapling grows out of a seed.

Man-made change: A doll is made from wood.

e. Desirable and undesirable change

Desirable change: Milk turns into curd.

Undesirable change: The iron parts in my bicycle get rusted. 

IX. Question based on Higher Order Thinking Skills

1. When a candle is lit the following changes are observed.

a. Wax melts.

b. Candle keeps burning.

c. The size of the candle decreases.

d. The molten wax solidifies

e. Which of the changes can be reversed? Justify your answer.

1. The molten wax can be changed into solid wax by cooling it. This is a reversible change.

2. The molten wax can be changed from its liquid state to solid state by cooling it. This is a reversible change.