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Course: Content items for courses > Unit 7

Lesson 2: Combination and decomposition reactions

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Exothermic and endothermic reactions

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John learns about combination reactions and spends a long day in the lab figuring out if they absorb or release heat.

Experiment $1$ ‍: He drops a sample of sodium ( $Na$ ‍) into a beaker containing water. The combination reaction produces sodium hydroxide ( $NaOH$ ‍) and hydrogen gas ( $H_{2}$ ‍).
Experiment $2$ ‍: He burns methane gas ( ${CH}_{4}$ ‍) as fuel. The combination reaction (recall that burning means reacting with oxygen, $O_{2}$ ‍) produces carbon dioxide ( ${CO}_{2}$ ‍) and water.

Help him identify the two chemical reactions.

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