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1. Jana uses marbles of different colors and sizes to represent atoms from different elements. How can she best model how compounds form in nature?
B. Combine marbles of different colors to represent elements bonding to form a compound.
2. Marco examines an unknown milky liquid that looks evenly mixed. When he filters it, small solid bits remain in the filter paper. What evidence shows the substance is not pure?
C. The filter left behind small solid pieces.
3.Kyla tests four solutions using litmus paper. When she accidentally spills one solution, the red paper turns blue. What can Kyla conclude about the spilled solution?
C. It is basic.
4. Different mixtures of bronze melt at different temperatures. Why does this happen?
B. They contain different amounts of copper and tin.
5. Several groups test the pH of water samples around the campus. Which conclusion would be scientifically valid?
B. Differences in readings suggest nearby materials affect pH.
6. Solid air freshener slowly disappears in a warm room. What happens to its molecules?
C. They lose energy and form a liquid.
7. Liam fries an egg and then stirs sugar into coffee. Which statements describe the changes?
D. Frying an egg is physical; dissolving sugar is chemical.
8. Which situation best shows a physical change?
C. Cutting a piece of wood.
9. Which example best supports the Law of Conservation of Mass?
A. Melting 10 g of ice into 10 g of water.
10. A metal reacts slowly with cool acid, but faster with warm acid. What explains this?
A. Warm acid increases particle collisions.
11. Two substances with total mass of 12 g react to form bubbles. After the reaction, the beaker shows 9 g of mass. What best explains this result?
A. Some matter was destroyed.
12. Which correctly identifies the samples?
A. Oxygen gas – element Carbon dioxide – compound Air – mixture
13. During an experiment, a wax candle melts and then solidifies again after cooling. What kind of change occurred?
A. Irreversible chemical change
14. A plastic spoon turns black and gives off a burnt odor when exposed to flame. What type of change happened?
C. Physical change due to heat
15. After burning dry leaves, the ashes weigh less than the original leaves. How does this still follow the Law of Conservation of Mass?
A. Some mass turned into smoke and gases that escaped.
16. When vinegar reacts with baking soda, bubbles form. What does this show?
B. A new gas formed during a chemical change.
