Lesson.3 Changes Around Us
Lesson.3 Changes Around Us
I. Choose the correct answer:
1. When ice melts to form water, change occurs in its
- position
- colour
- state
- composition
Ans : state
2. Drying of wet clothes in air is an example of
- Chemical change
- Undesirable change
- irreversible change
- physical change
Ans : physical change
3. Formation of curd from milk is
- reversible change
- a fast change
- an irreversible change
- an undesirable change
Ans : an irreversible change
4. Out of the following an example of a desirable change is
- rusting
- change of seasons
- earthquake
- flooding
Ans : change of seasons
5. Air pollution leading to Acid rain is a
- reversible change
- fast change
- natural change
- human made change
Ans : human made change
II. Fill in the blanks
1. Magnet attracts iron needle. This is __________________ change. (a reversible / an irreversible)
Ans : a reversible
2. Boiling of egg results in __________________ change. (a reversible / an irreversible)
Ans : an irreversible
3. Changes that are harmful to us are __________________. (desirable / undesirable)
Ans : undesirable
4. Plants convert Carbon-di-oxide and water into starch. This is an example of change. __________________ (natural / human made)
Ans : natural
5. Bursting of fire crackers is a change whereas germination of seeds is a change __________________ . (slow / fast)
Ans : fast
III. True or False. If False, give the correct statement
1. Growing of teeth in an infant is slow change.
Ans : True
2. Burning of match stick is a reversible change
Ans : False
Cu. An : Burning of match stick is irreversible change
3. Change of New moon to Full moon is human made.
Ans : False
Cu. An : Change of New moon to Full moon is Natural made
4. Digestion of food is a physical change.
Ans : False
Cu. An : Digestion of food is a chemical change
5. In a solution of salt in water, water is the solute
Ans : False
Cu. An : In a solution of salt in water ,water is the solvent
IV. Analogy
1. Curdling of milk : irreversible change :: Formation of clouds : ________change
Ans : reversible
2. Photosynthesis : __________ change :: burning of coal : Human – made change
Ans : natural made
3. Dissolving of glucose : reversible change :: Digestion of food: ___________ change
Ans : irreversible
4. Cooking of food : desirable change :: decaying of food : _________change
Ans : undesirable
5. Burning of matchstick :_______ change: Rotation of the Earth : Slow change
Ans : fast
V. Circle the odd one out. Give reason for your choice
1. Growth of a child, Blinking of eye, Rusting, Germination of a seed
Ans : Rusting
Reason : Rusting is chemical change others are slow change
2. Glowing of a bulb, lighting of a Candle, breaking of a coffee mug, curdling of milk
Ans : curdling of milk
Reason : curdling of milk irreversible change others are fast change
3. Rotting of an egg, condensation of water vapour, trimming of hair, Ripening of fruit
Ans : Rotting of an egg
Reason : Rotting of an egg is Undesirable change others are slow change
4. Inflating a balloon, popping a balloon, fading of wall paint, burning of kerosene
Ans : fading of wall paint
Reason : fading of wall paint is slow change others are fast change
VI. Give very short answer
1. What kind of a change is associated with decaying of a plants?
decaying of a plants is natural change.
2. You are given some candle wax. Can you make a candle doll from it? What kind of change is this?
Yes, reversible change.
3. Define a slow change.
Changes which take place over a long period of time ( hours / days / months / years ) are known as Slow changes.
4. What happens when cane sugar is strongly heated? Mention any two changes in it.
water molecule evaporated from the canesugar charring occours Irreversible change and chemical change.
5. What is a solution?
solute is dissolved in a solvent it forms a solution
VII. Give short answer
1. What happen when paper is burnt? Explain.
Changes which take place within a short period of time (seconds or minutes) are known as fast changes.burning of paper is fast change
2. Can deforestation be considered a desirable change? Explain.
Undesirable change, The changes which are harmful to our environment.
3. What type of changes is associated with germination of a seed? Explain
Ans: slow change,Changes which take place over a long period of time ( hours / days / months / years ) are known as Slow changes. Examples: growth of nail and hair, change of seasons, germination of seed
VIII. Answer in detail
1. Give one example in each case that happens around you.
a. Slow and fast change
Slow:
Examples : growth of nail and hair, change of seasons, germination of seed
Fast:
Examples : Bursting of balloon, breaking of glass, bursting of fire crackers, burning of paper.
b. Reversible and irreversible change
Reversible changes:
Examples: Touch me not plant (Responding to touch), stretching of rubber band, melting of ice.
Irreversible changes:
Examples : Change of milk into curd, digestion of food, making idly from batter
c. Physical and chemical change
Physical changes:
Example : Melting of ice, the solution of salt or sugar, stretching of rubber band
Chemical changes:
Examples : Burning of wood, Popping of popcorn, Blackening of silver ornaments, and Rusting of iron
d. Natural and man-made change
Natural changes:
Examples : Rotation of the earth, Changing phases of the Moon, Rain
Man-made changes:
Examples : Cooking, Deforestation, Cultivating crops, construction of building.
e. Desirable and undesirable change
Desirable changes:
Examples : Ripening of fruit, growth of plants, cooking of food, milk changing to curd.
undesirable changes:
Examples : Deforestation, decaying of fruit, rusting of iron