8th Grade Chemistry Unit Benchmark Review

1. What class of solids is made up of regularly, repeating subunits of tightly packed, orderly arrangement of atoms, ions, and molecules?

• a metallic solid
• a nonmetallic solid
• a crystalline solid
• an amorphous solid

2. Nitrogen has a melting point of -210.0 degrees C and a boiling point of -195.8 degrees C. What is nitrogen's state of matter at -215 degrees C?

• liquid
• solid
• plasma
• gas

3. Which of the following chemical formulas represents an element, but not a molecule?

• C
• H2O
• H2
• NH3

4. Which statement below is also true of the rearrangement of atoms?

• The amount of matter is conserved.
• The amount of matter decreases.
• The number of substances increases.
• The number of substances is conserved.

5. What does the data show is occurring?

• The hydrochloric acid and magnesium metal react to form a soluble compound.
• The hydrochloric acid and magnesium metal do not react.
• The hydrochloric acid and magnesium metal react to form a precipitate.
• The hydrochloric acid and magnesium metal react to form a gas.

6. Which picture correctly represents a group of molecules. Select the correct image.

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7. Which of the following statements best describes the Law Of Conservation of Mass?

• Atoms are created by some reactions and destroyed by others.
• Energy is created as atoms and destroyed in chemical reactions.
• Every atom destroyed in a chemical reaction must be replaced.
• Atoms cannot be created or destroyed by chemical reactions.

8. An orange is left on the kitchen counter. Which of the following would I do if I wanted to slow down/ decrease the movement/speed of the particles?

• Put the orange in the window on a sunny day
• Put the orange in the microwave or the oven.
• Eat for dinner.
• Put the orange in the freezer.

9. June is building a model of a water molecule with balls and sticks. Which of these is the best model for her to build. (Hint: A molecule is two or more atoms bonded together. A water molecule (H2O) is two hydrogen atoms and an oxygen atom bonded together.)

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10. Molecular motion is a measure of the movement of molecules in a substance. Molecular motion varies between the different states of matter. For example, the molecules in ___________ move more/faster than the molecules in ____________.

• liquids, gases
• gases, solids
• solids, liquids
• solids, gases