Particulate Nature of Matter Class 8 - Chapter 7 (Curiosity)

Q 1
Question
Choose the correct option. The primary difference between solids and liquids is that the constituent particles are:
(i) closely packed in solids, while they are stationary in liquids.
(ii) far apart in solids and have fixed position in liquids.
(iii) always moving in solids and have fixed position in liquids.
(iv) closely packed in solids and move past each other in liquids.
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Q 2
Question
Which of the following statements are true? Correct the false statements.
(i) Melting ice into water is an example of the transformation of a solid into a liquid.
(ii) Melting process involves a decrease in interparticle attractions during the transformation.
(iii) Solids have a fixed shape and a fixed volume.
(iv) The interparticle interactions in solids are very strong, and the interparticle spaces are very small.
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Q 3
Question
Choose the correct answer with justification. If we could remove all the constituent particles from a chair, what would happen?
(i) Nothing will change.
(ii) The chair will weigh less due to lost particles.
(iii) Nothing of the chair will remain.
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Q 4
Question
Why do gases mix easily, while solids do not?
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Q 5
Question
When spilled on the table, milk in a glass tumbler flows and spreads out, but the glass tumbler stays in the same shape. Justify this statement.
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Q 6
Question
Represent diagrammatically the changes in the arrangement of particles as ice melts and transforms into water vapour.
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Q 7
Question
Draw a picture representing particles present in the following: (i) Aluminium foil (ii) Glycerin (iii) Methane gas.
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Q 8
Question
Observe Fig. 7.16a which shows the image of a candle that was just extinguished after burning for some time. Identify the different states of wax in the figure and match them with Fig. 7.16b showing the arrangement of particles.
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Q 9
Question
Why does the water in the ocean taste salty, even though the salt is not visible? Explain.
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Q 10
Question
Grains of rice and rice flour take the shape of the container when placed in different jars. Are they solids or liquids? Explain.
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Project 1
Project
Fix a balloon over the neck of a bottle and put the bottle in hot water. Explore what will happen?
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Key Points
The balloon inflates as the warm air expands.
Key Points / Good Practices
Hot water warms the air inside the bottle.
On heating, the air particles gain energy and move faster.
They spread out and need more space.
The expanding air pushes into the balloon and inflates it.
Try cool water too and compare what happens.
Handle the hot water carefully with an adult's help.
Heating makes gas particles spread out, so the warm air inflates the balloon.

Project 2
Project
Design and create simple models to represent particles of solids, liquids, and gases showing interparticle spacing using clay balls, beads, etc.
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Key Points
Use spacing to show each state clearly.
Key Points / Good Practices
For a solid, pack the clay balls tightly together.
For a liquid, leave a little more space between balls.
For a gas, spread the balls far apart.
Use the same size balls so only spacing changes.
Label each model clearly as solid, liquid, or gas.
Glue or trays help hold the arrangement in place.
The models should show packing increasing from tight (solid) to wide (gas).

Project 3
Project
Pretend to be particles of solids, liquids, and gases, at different temperatures—create and perform a role-play/dance showing particles in motion.
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Key Points
Show motion increasing with temperature.
Key Points / Good Practices
For a solid, stand close together and only sway in place.
For a liquid, stay near but move around each other.
For a gas, run freely all over the space.
When "heated", move faster to show added energy.
Use simple music to keep the timing together.
Explain each scene to the audience before performing.
The role-play should show particles moving more as the state changes from solid to gas.

Project 4
Project
Debate in the class — ‘Gases can spread and fill all the available space’. Is this property of gases beneficial or harmful?
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Key Points
Spreading gases can be both helpful and harmful.
Key Points / Good Practices
Beneficial: the smell of food warns us and helps us enjoy it.
Beneficial: cooking gas spreads to burn evenly.
Beneficial: room fresheners and perfumes spread quickly.
Harmful: a gas leak can spread danger fast.
Harmful: polluting gases spread through the whole air.
Conclude that the property is useful but must be handled safely.
A balanced debate shows the spreading of gases is helpful but can be harmful if unsafe.