Practice Phase Change in Chemistry

Use these practice problems to test your method after reviewing the concept explanation and worked examples.

Quick Recap

A transition from one state of matter to another, caused by adding or removing energy.

Add enough heat and a solid melts to liquid, then boils to gas. Remove heat and the reverse happens.

Example 1

easy
Name the six phase changes and indicate whether each absorbs or releases energy.

Example 2

medium
Why does the temperature remain constant during a phase change, even though heat is being added?

Example 3

easy
What phase change occurs when dry ice (\text{CO}_2) goes directly from solid to gas?

Example 4

hard
A heating curve shows a substance warming from -20°\text{C} to 120°\text{C}. It has a melting point of 0°\text{C} and a boiling point of 100°\text{C}. Explain why there are two flat (horizontal) sections on the curve, even though heat is continuously added.
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