Detailed Instructions: Given a scientific passage and an answer, generate a question for the given answer.
Problem:Passage: A compound has different properties than the substances it contains. For example, hydrogen and oxygen are gases at room temperature. But when they combine chemically, they form liquid water. Another example is table salt, or sodium chloride. It contains sodium and chlorine. Sodium is a silvery solid that reacts explosively with water, and chlorine is a poisonous gas (see Figure below ). But together, sodium and chlorine form a harmless, unreactive compound that you can safely sprinkle on food. Answer: gas
Solution:
In what form of matter is hydrogen at room temperature?