1. Where does the heat used to re-inflate a balloon come from? 2.When a cup of hot coffee cools down, where does the heat go?

3. How can you keep a cup of coffee warm?

substituting a hydrogen atom with a halogen in a hydrocarbon:

- the single bond remains single. a is wrong.

- the bond with hydrogen is as strong as with a halogen. c is wrong

- a hydrocarbon is saturated if there is no double bond. we do not know that so d is wrong.

- carbon will always have four valence electrons. e is wrong.

by elimination, the correct answer is b. the boiling point of the new compound increases.

c

explanation:

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