Question

a teacher asks her students to classify the substances listed in the table shown as elements, compounds, or mixtures.

substance	formula
ammonia	nh₃
water	h₂o

a student claims that all of the substances are compounds. which statement correctly describes the student’s claim?

• the student’s claim is correct because a substance that contains more of 2 of the same atom is a compound.
• the student’s claim is correct because the atoms in the substances are chemically combined to form a compound.
• the student’s claim is incorrect because the atoms in the substances are physically combined to form a mixture.
• the student’s claim is incorrect because a substance that contains more than one element is always a mixture.

Explanation:

To determine the correctness of the student's claim, we analyze each option:

• Option 1: A compound is made of different atoms, not the same atom. So this is incorrect.
• Option 2: Compounds are formed when atoms of different elements are chemically bonded. Sucrose ($\ce{C_{12}H_{22}O_{11}}$), ammonia ($\ce{NH_3}$), and water ($\ce{H_2O}$) all have atoms chemically combined (different elements), so they are compounds. This option's reasoning is correct.
• Option 3: The atoms in these substances are chemically combined (forming compounds), not physically combined (which would be a mixture). So this is incorrect.
• Option 4: A substance with more than one element can be a compound (if chemically combined), not always a mixture. So this is incorrect.

Answer:

B. The student’s claim is correct because the atoms in the substances are chemically combined to form a compound.