Text Book Back Questions and Answers - Chapter 3 Changes Around Us Term 2 6th Science Guide Samacheer Kalvi Solutions - SaraNextGen [2024-2025]

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On April 24, 2024, 11:35 AM

Textual Evaluation : Chapter 3 - Changes Around Us - Term 2 - 6th Science Guide Samacheer Kalvi Solutions
I. Choose the appropriate answer:
Question $1 .$
When Ice melts to form water, change occurs In its
(a) position
(b) colour
(c) state
(d) composition
Answer:
(c) state

Question $2 .$
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

Question $3 .$
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

Question $4 .$
Out of the following an example of a desirable change is
(a) rusting
(b) change of seasons
(c) earthquake
(d) flooding
Answer:
(b) change the seasons

Question 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 _________change (a reversible/anirreversible)
2. Boiling of egg results in _________change, (a reversible / an irreversible)
3. Changes that are harmful to us are _________(desirable / undesirable)
4. Plants convert Carbon-di-oxide and water into starch. This is an example of _________change, (natural / human made).
5. Bursting of fire crackers is a _________change whereas germination of seeds is a_________ change, (slow / fast)

Answers:
1. reversible
2. an irreversible
3. undesirable
4. natural
5. fast, slow

III. True or False. If False, give the correct statement:
Question $1 .$
Growing of teeth in an infant is slow change.
Answer:
True

Question 2.
Burning of match stick is a reversible change.
Answer:
False, Burning of match stick is an irreversible change.

Question $3 .$
Change of New moon to Full moon is human made.
Answer:
False, Change of new moon to full moon is natural change.

Question $4 .$
Digestion of food is a physical change.
Answer:
False, Digestion of food is a chemical change.

Question $5 .$
In a solution of salt in water, water is the solute.
Answer:
False, In a solution of salt in water, water is the solvent

IV. Analogy:
Question $1 .$
Curdling of milk : irreversible change :: Formation of clouds : _______change.
Answer:
reversible

Question $2 .$
Photosynthesis : _______change :: burning of coal: Human - made change.
Answer:
natural

Question $3 .$
Dissolving of glucose: reversible change:: Digestion of food: _______change
Answer:
irreversible

Question $4 .$
Cooking of food : desirable change :: decaying of food : _______change
Answer:
undesirable

Question $5 .$
Burning of matchstick : _______change: Rotation of the Earth : Slow change

Answer:
Fast

V. Circle the odd one out. Give reason for your choice:
Question $1 .$
Growth of a child, Blinking of eye, Rusting, Germination of a seed.
Answer:
Rusting
Reason: Rusting is undesirable change. Others three are desirable changes.

Question $2 .$
Glowing of a bulb, lighting of a Candle, breaking of a coffee mug, curdling of milk.
Answer:
breaking of a coffee mug.
Reason : Breaking of a coffee mug is undesirable change. Other three are desirable changes.

Question $3 .$
Rotting of an egg, condensation of water vapour, trimming of hair, Ripening of fruit.
Answer:
Rotting of an egg.
Reason : Rotting of an egg is undesirable change. Other three are desirable changes.

Question $4 .$
Inflating a balloon, popping a balloon, fading of wall paint, burning of kerosene.
Answer:
Inflating a balloon.
Reason : Inflating a balloon is reversible change. Other three are irreversible changes.

VI. Give very short answer:
Question $1 .$
What kind of a change is associated with decaying of a plants?
Answer:
Decaying of plants is associated with slow change and chemical change.

Question $2 .$
You are given some candle wax. Can you make a candle doll from it? What kind of change is this?
Answer:
Yes, I can. It is a physical (reversible) change.

Question $3 .$
Define a slow change.
Answer:

Changes which take place over a long period of time (hours/days/months/years) are known as slow changes.

Question $4 .$
What happens when cane sugar is strongly heated? Mention any two changes in it.
Answer:
1. Sugar is basically Sucrose.
2. The molecular formula of Sugar is $\mathrm{C}_{12} \mathrm{H}_{22} \mathrm{O}_{11}$ (or) $\mathrm{C}_{12}\left(\mathrm{H}_{2} \mathrm{O}\right)_{11}$.
3. When sugar is heated, it loses all water molecules and decomposes to carbon.
4. Chemical change;
5. Irreversible change

Question $5 .$
What is a solution?
Answer:
When a solute is dissolved in a solvent, it forms a solution.
Solute $+$ solvent $\rightarrow$ solution.

VII. Give short answer:
Question $1 .$
What happens when paper is burnt? Explain.
Answer:
Burning of paper takes place within a short period of time (seconds or minutes) So, it is a fast change.

Question $2 .$
Can deforestation be considered a desirable change? Explain.
Answer:
No, it is an undesirable change, and it is a human made change. Deforestation leads to decreasing rainfall, and leads to global warming.

Question $3 .$
What type of changes is associated with germination of a seed? Explain
Answer:
1. Germination of seed is a slow change.
2. Changes which take place over a long period of time (days) are known as Slow changes.

VIII. Answer In detail:
Question $1 .$
Give one example in each case that happens around you.

a. Slow and fast change
b. Reversible and irreversible change
c. Physical and chemical change
d. Natural and man-made change
e. Desirable and undesirable change

Answer:

IX. Questions Based on Higher Order Thinking Skills.
Question 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.
Answer:
a. Wax melting is a reversible change.
d. "The molten wax solidifies" is a reversible change.
These two changes can be reversible to get back the original state. So the above two changes are reversible changes.

In-Text Activities
Fill in the gaps:
Answer:

Activity 1
Question $1 .$
What happens when you blow air into a balloon?

Is there change in size? [ ] Yes [ ] No
Answer:
$[\sqrt{ }]$ Yes
Is there change in shape? [ ] Yes [ ] No
Answer:
$[\sqrt{]}$ Yes
Is there any other change? [ ] Yes [ ] No
Answer:
$[\sqrt{]}$ No

Activity 2
Question $1 .$
Look at the pictures and discuss about the duration for the changes to take place.

Answer:
1. Child growing - Slow change
2. Rusting of iron - Slow change
3. Bulb glowing - Fast change
4. Bursting of fire crackers $-$ Fast change

Activity 3
Question $1 .$
Try to make a boat and an aeroplane one by one using the same piece of paper. This means the change of shape discussed here is reversible.

Answer:
The change is reversible, because we make boat and aeroplane in the same piece of paper. Activity to be done by the students themselves.

Activity 4
Question $1 .$
What kind of changes are they?
(a) Burning of a candle.
(b) Piercing a balloon with a pin.

Answer:
(a) Reversible change
(b) Irreversible change.

Activity 5
Question $1 .$
Take an apple and cut it into two halves. Cut one half into pieces and share it with your friends.

Is there any change in the composition of the Apple while cutting?
No, only the shape and size have changed. This can be called a Physical change.
Leave the other half on the table for some time. You can see brown patches formed on the cut surface because of the reaction between some substances in the apple and the air around it. This is a Chemical change.
Answer:
Activity to be done by the students themselves.

Activity 6
Take half a cup of water, add one spoon full of sugar and stir well.

(a) What do you observe?
(b) What happened to the sugar?
(c) Where is it gone?
(d) The solute in the above solution is
(e) The solvent in the above solution is
(f) Have you seen a glass of water and a glass of sugar solution looking alike?
Answer:
(a) I observe sugar solution is there.
(b) The sugar is dissolved in the water.
(c) The sugar particle is mixed with water molecules.
(d) The solute is sugar.
(e) The solvent is water
(f) Yes.

Activity 7
Question 1.
Look at the pictures and write whether they are Physical or Chemical changes.

Answer:
i. Chemical change
ii. Physical change
iii. Physical change
iv. Chemical change

Activity 8
Question $1 .$
Look at the pictures and write whether they are desirable or undesirable changes.

Answer:
i. forest fire - undesirable change
ii. decaying of fruit - undesirable change
iii. egg to chicken - desirable change
iv. wind mills - desirable change.

Activity 9
Question $1 .$
Identify the type of changes.
Natural / Human made

Answer:
i. Floods - Natural change
ii. Carpentry - Human made change
iii. Planting of seedlings - Human made change iv. Land slides - Natural change

Additional Questions
I. Choose the correct answer:
Question $1 .$
Growth of seed into sapling is _______ change
(a) slow
(b) chemical
(c) reversible
(d) undesirable
Answer:
(a) slow

Question $2 .$
The softening of vegetables by cooking is a (an)
(a) Fast change
(b) Chemical change
(c) Artificial change
(d) Reversible change

Answer:
(c) Artificial change

Question $3 .$
Which of the following is not a man-made change?
(a) Burning of fuels
(b) Drying of clothes
(c) Tearing of paper
(d) Change of day and nigh
Answer:
(d) Change of day and night

Question $4 .$
Sublimation of Iodine is a
(a) Chemical change
(b) Physical change
(c) Natural change
(d) Undesirable change
Answer:
(b) physical change

Question 5 .
Raining is a change
(a) human made
(b) undesirable
(c) slow
(d) natural
Answer:
(d) natural

II. Fill in the blanks:
1. _______ changes which take place within a short period of time. (Fast/Slow)
2. When 'Touch me not' plant is touched by us, _______changes occur.
(reversible/irreversible)
3. Tearing of sheet of paper into pieces is_______ By the process of Heating of water, change. (physical / chemical).
4. By the process of Heating of water,_______ is obtained (ice/steam)
5 ._______ is the substance that is dissolved in a solvent. (Solute/Solvent)
6. The changes in which new substance with new chemical properties are formed are_______ changes. (physical / chemical).
7. Deforestation is _______change. (Natural/human made)
Answers:

1. Fast
2. reversible
3. physicall
4. steam
5. Solutel
6. chemical
7. human made

III. Find whether the following sentences are true or false. If false Correct the statement:
Question $1 .$
The difference between initial state and the final state is called change.
Answer:
True.

Question $2 .$
Gas exists in three states as solid, liquid and gas.
Answer:
False. Water exists in three states as solid, liquid, gas.

Question $3 .$
Water into steam on heating is called freezing.
Answer:
False. Water into steam on heating is called vaporisation.

Question $4 .$
When solute is dissolved in a solvent it forms a solution.
Answer:
True.

Question $5 .$
Chemical change is a temporary change .
Answer:
False. Chemical change is a permanent change, (or) Physical change is a temporary change.

Question $6 .$
Natural changes which take place in nature on their own, are beyond the control of human being.
Answer:
True.

Question $7 .$
Construction of building is a Natural change.
Answer:
False. Construction of building is a human made change.

IV. Analogy:
Question $1 .$
Germination of seed: slow change.
Breaking of glass:_______
Answer:
Fast change

Question $2 .$
Irreversible change : Making idly front batter.
Reversible change:_______
Answer:
Stretching of Rubber band

Question $3 .$
Melting of ice : Physical change.
Popping of popcorn :_______
Answer:
Chemical change

Question $4 .$
Melting : ice into water on heating,
freezing:_______
Answer:
water into ice on cooling.

Question $5 .$
Changing of phases of the moon : Natural changes.
Cultivation of paddy :_______
Answer:
Human made change.

V. Match the following:

Answer:
i. $-\mathrm{e}$

i1. $-\mathrm{d}$
iii $-\mathrm{a}$
iv. $-b$
V. $-\mathrm{c}$

VI. Give short answer:
Question $1 .$
Mention any three examples of fast change?
Answer:
1. Bursting of balloon
2. Breaking of glass
3. Burning of paper

Question $2 .$
What is reversible change? Give example.
Answer:
Changes which can be reversed, to get back the original state, are known as reversible changes. Eg.: Melting of ice, stretching of rubber band.

Question $3 .$
Give some examples for physical change.
Answer:
1. Melting of ice
2. The solution of salt (or) sugar
3. Stretching of rubber band.

Question $4 .$
Whatjs freezing? Give example.
Answer:
The conversion of liquid into solid by cooling is called freezing. Ex. Water into ice cubes.

Question $5 .$
Define sublimation.
Answer:
The change of state from solid to gas directly is called sublimation.

Question $6 .$
Water is known as universal solvent. Why?
Answer:
Water dissolves a wide range of substances. So it is called as universal solvent.

Question $7 .$
What is the meaning of natural changes? Give example.
Answer:
Changes which take place in nature on their own and are beyond the control of human beings are known as natural changes. Ex.: Rotation of earth, Raining.

Question $8 .$
What is artificial changes? Give example.
Answer:
The changes which are brought about by human beings are known as human made or artificial changes. Ex.: Construction of bridges, Road construction, Cooking.
 

VII. Answer in detail:
Question $1 .$
Tabulate the difference between physical and chemical changes.
Answer: