Class 5 General Science (G.Sc.) Notes: Unit-5: Physical and chemical changes: Solved Exercise ( MCQs, Questions and Answers)

General Science (G.Sc.) Class 5 Notes

Based on the Single National Curriculum, PK

(New Book/New Syllabus for 2023-2024 Exams and onward)

National Book Foundation
as
Federal Textbook Boards, Islamabad

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"1. Tick ( ✓ ) the Correct Answers"

i. The change of milk into yoghurt is

(a) physical change
(b) climate change
(c) chemical change
(d) change of colour

... Answer is (c)  chemical change
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ii. Why a person painted his iron gate?

    (1) To save it from rusting.

    (2) To save it from sunlight

    (3) To make it beautiful

    (4) To save it from water

Out of these which answer is correct?

(a) 1 and 2
(b) 1 and 3
(c) 2 and 3
(d) 1 and 4

... Answer is (d)  1 and 4
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iii. Which factor will NOT affect the dissolving of sugar in water?

(a) Adding salt to the water
(b) Making sugar powder by grinding
(c) heating water and sugar
(d) stirring water and sugar

... Answer is (a) Adding salt to the water
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v. What type of change is it when the metal expands on heating?

(a) permanent
(b) chemical
(c) physical
(d) irreversible

... Answer is (c) physical
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2. "Write Short Answers"

Q(i). Explain evaporation by giving examples from everyday life. 

Ans: 

Evaporation:

"The change of water into vapours is called Evaporation". 

Examples:

i. Wet surfaces become dry due to evaporation as water moves in the surrounding air.

2. Evaporation takes place on the surface of oceans, canals, rivers and leaves of plants. 

Q(ii). Define condensation?

Ans:

Condensation:

"The change of gas into liquid is called condensation." 

Water drops at the external surface of the glass can be seen because water vapours from the air touch the glass's surface and lose heat. As a result, these vapours change into liquid and stick to the external surface of the glass.

Q(iii). What is rusting and which type of change is this? 

Ans:

Rusting:

The change that has occurred on the surface of iron is due to the action of oxygen and water and is called rusting. Due to this reaction, the colour of iron is changed. 

Iron + Oxygen + Water = Rusting 

It is a chemical change because a new substance iron oxide is formed. 

Q(iv). Give an example of a chemical change in which carbon dioxide is produced.

Ans: Natural gas (Methane) reacts with Oxygen in the atmosphere and produces water and carbon dioxide. 

Q(v). Explain three states of matter and their interconversion.

Ans: There are Three states of matter. 

i. Solid 

ii. Liquid

iii. Gas

Interconversion of matter is a process by which matter changes from one state to another and back to its original state without changing its chemical composition. Solid can be converted into a liquid by heating. Similarly, liquid can be converted into gases and gases can be converted into solid cooling.

3. Constructed Response Questions:

Q1- Weigh one fourth of a glass of vinegar and tea spoon of baking soda. Then mix them together. As a result, bubbles will be formed. Weigh this compound again. Now its weight will become less than the previous one. How will you explain the loss of the weight?

Ans: 

Mixing vinegar and baking soda produces a chemical reaction. The acetic acid in vinegar reacts with the basic sodium bicarbonate of baking soda. This produces carbonic acid, which quickly decomposes to water and carbon dioxide (a gas) which bubbles out of the solution. After releasing gas bubbles weight of the compound becomes less than the previous one.

Q2- A mixture of (a) vinegar and baking soda, (b) vinegar and boiling water both Produce bubbles. Out of the two, one is a chemical change and the other is a physical change. Explain.

Ans: 

(a) A mixture of vinegar and baking soda is a chemical change because bubbles released during the reaction are of carbon dioxide gas. This reaction is irreversible.

(b) Vinegar and boiling water produce bubbles of water vapors which is a physical change.

Q3- A student weighs a piece of ice and then allows it to melt. In your opinion what will be the Weight of water and why?

Ans: 

There will be no change in the weight of water because no particles are destroyed and none are added. In addition, the size and shape of the particles does not change. Therefore matter and mass (or weight) are conserved (stay the same) during the process of phase change from solid (ice) to liquid (water).

4."INVESTIGATE QUESTIONS"

Q1. Why formation of fertilizers from Leaves is a chemical change? 

Ans. The formation of fertilizers from leaves is called Manures. 

Its formation is considered a chemical change because manure formed has a different composition of leaves. It is an organic matter used as a fertilizer in agriculture. It is prepared using green leaves and the process cannot be reversed. It is a chemical I change.

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1.  5th Class: English Notes

2.  5th Class: Social Study (S.St.) Notes

3.  5th Class: General Science (G.Sc.) Notes

4.  5th Class: Urdu (اُردو) Notes

5.  5th Class: Islamiyat (اسلامیات) Notes

6.  5th Class: Mathematics Notes

7.  Easy English Grammar Notes

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