instruction:
In this task, you need to write a topic word from the given fact. The topic word must have at least one word overlap with the given fact. The topic word often involves adding a new word from a related concept. In your topic word, use at least one word from the given fact. Topic words with two or more words work best.
question:
Fact: melting is when solids are heated above their melting point.
answer:
melting dissolve.


question:
Fact: a ruler is used for measuring the length of an object.
answer:
Length of object.


question:
Fact: when a gas in an open container evaporates , that gas spreads out into the air.
answer:

air contamination.