Which of the following substances is in the gaseous state under standard conditions?

Study for the Cambridge Science – States of Matter Test. Prepare with flashcards and multiple choice questions, with hints and explanations for each question. Ready yourself for your exam!

Multiple Choice

Which of the following substances is in the gaseous state under standard conditions?

Explanation:
At standard conditions, a substance’s state depends on whether its phase change temperatures sit above or below 25°C and 1 atm. Helium has a boiling point of about -269°C, which is far below room temperature. That means, at 25°C and 1 atm, helium exists as a gas. Water, at 25°C, is liquid because its boiling point is 100°C and its melting point is 0°C. Ice is solid below 0°C, so at standard conditions it’s not a gas. Mercury becomes a liquid at room temperature since its melting point is about -39°C and its boiling point is about 357°C. Thus, the substance in the gaseous state under standard conditions is helium.

At standard conditions, a substance’s state depends on whether its phase change temperatures sit above or below 25°C and 1 atm. Helium has a boiling point of about -269°C, which is far below room temperature. That means, at 25°C and 1 atm, helium exists as a gas.

Water, at 25°C, is liquid because its boiling point is 100°C and its melting point is 0°C. Ice is solid below 0°C, so at standard conditions it’s not a gas. Mercury becomes a liquid at room temperature since its melting point is about -39°C and its boiling point is about 357°C.

Thus, the substance in the gaseous state under standard conditions is helium.

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