D. Answer these questions. 1. Why do solids have a fixed shape? 2. Why do liquids flow? 3. Write two differences between liquids and gases. 4. When do we say that liquids are miscible? 5. What is a physical change? Give two examples. 6. What is a chemical change? Give two examples. 7. Give three characteristic features of a chemical change.
Answers
Answer:
1)- Solids have a fixed shape and a fixed size Because the particles cannot move around.
2)- Liquid takes the shape of the container in which it is kept. If we keep the liquid in a bottle, it will take the shape of a bottle. ... Due to this free movement of molecules, liquid can flow.
3)- liquid- intermolecular space is more, do not have definite shape but have definite volume.
gas - intermolecular space are more than in liquids, do not have definite shape and volume.
4)- if they mix or dissolve completely in each other to give a single liquid phase and are difficult to separate.
5)- A change in which a substance undergoes a change in its physical properties is called a physical change. A physical change is generally reversible. In such a change no new substance is formed.
6)- usually irreversible chemical reaction involving the rearrangement of the atoms of one or more substances and a change in their chemical properties or composition, resulting in the formation of at least one new substance: The formation of rust on iron is a chemical change.
7)- A new substance is formed.
It is normally irreversible.
Change in colour.
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1. the molecules in solids have fixed position and strong intermolecular force acting between them. therefore solid has a fixed shape.
2. liquids flow because the intermolecular force between molecules are work enough to allow the molecules to move around relative to one another.
3. Liquid
a) it has definite volume but no definite shape.
b) always flows from higher to lower level.
Gases
a) it has no definite shape and volume.
b) flows in all direction.
4. two liquids are said to be miscible if they mix or dissolve completely in each other to give a single liquid phase and are difficult to separate.
5. a change in which a substance undergoes a change in its physical properties is called a physical change.
e.g. liquid convert into ice
ice convert into water
6. a change in which one or more new substance are formed is called a chemical change.
e.g. digestion of food in our body,
ripening of food.
7. change in colour
temperature change
formation of a gas