Review the key concepts, formulae, and examples before starting your quiz.
🔑Concepts
Matter can change from one state to another (Solid, Liquid, Gas) by heating or cooling.
Melting (Fusion): The process of changing a into a state on heating. For example, Ice changing to water at .
Vaporization (Boiling): The process of changing a into a (vapor) state on heating. Water boils at .
Condensation: The process of changing a into a state on cooling. This is the reverse of vaporization.
Freezing (Solidification): The process of changing a into a state on cooling. Water freezes into ice at .
During these processes, the temperature of the substance typically remains constant until the change of state is complete.
The chemical formula for water in all three states (Ice, Water, Steam) remains .
📐Formulae
💡Examples
Problem 1:
Explain what happens to the molecules of ice when it is heated to become water.
Solution:
The process is called .
Explanation:
When ice () is heated, the molecules gain energy and start vibrating faster. They overcome the strong forces of attraction holding them in a fixed position and begin to move around, turning the ice into water ().
Problem 2:
Why do we see 'steam' coming out of a kettle when water is boiled?
Solution:
(Vaporization).
Explanation:
When water is heated to , it reaches its boiling point. The molecules gain enough energy to escape into the air as water vapor or steam.
Problem 3:
What is the phenomenon where dew drops form on grass during a cold morning?
Solution:
.
Explanation:
Water vapor present in the air (Gas) touches the cold surface of the grass. It loses heat energy and changes back into tiny droplets of water (Liquid).