1. A student observes that plants in a sunny window grow taller than plants in a shady corner. The student states, "Sunlight causes plants to grow taller." What part of a scientific explanation is this statement?
- A. The evidence
- B. The procedure
- C. The claim
- D. The variable
2. A scientist claims the local pond is polluted. Which of the following statements provides the strongest scientific evidence to support this claim?
- A. The pond has a strange smell.
- B. Lab tests show high bacteria levels.
- C. A nearby resident thinks the water is dirty.
- D. The water looks much greener than it did last year.
3. An engineer says, "I believe the bridge is unsafe because my inspection showed several cracked support beams." Which part of this statement represents the claim?
- A. "I believe"
- B. "the bridge is unsafe"
- C. "my inspection showed"
- D. "several cracked support beams"
4. An investigator is determining why a freezer has stopped working. Which of the following is a piece of evidence, rather than a claim?
- A. The freezer's cooling system is broken.
- B. The temperature inside the freezer is 40°F.
- C. The freezer needs to be replaced with a new model.
- D. There is an electrical fault in the appliance.
5. In the context of a scientific explanation, what is a "claim"?
- A. The data collected during an experiment.
- B. A proposed answer to a scientific question or problem.
- C. A step-by-step procedure for an investigation.
- D. A guess made before any observations are recorded.
6. Which statement best describes the relationship between the temperature of a gas and the kinetic energy of its molecules?
- A. As temperature decreases, the kinetic energy of the molecules increases.
- B. As temperature increases, the kinetic energy of the molecules increases.
- C. Temperature and the kinetic energy of molecules are unrelated properties.
- D. Temperature only affects kinetic energy when the gas is about to change phase.
7. For a gas to condense into a liquid, which two conditions are fundamentally required at the molecular level?
- A. Energy must be added to the system, and molecular attractions must be overcome by the molecules.
- B. The temperature must be raised above the boiling point, and the pressure must be increased significantly.
- C. The molecules must gain a large amount of kinetic energy, allowing them to stick together more easily.
- D. Energy must be removed from the system, allowing molecular attractions to pull the slower-moving molecules together.
8. Why does lowering the temperature of a gas promote condensation?
- A. It causes the molecules to repel each other more strongly, forcing them into a smaller volume.
- B. It decreases the average kinetic energy of the molecules, making molecular attractions more effective.
- C. It increases the space between molecules, giving them room to form liquid droplets.
- D. It breaks the molecular attractions that are keeping the substance in a gaseous state.
9. A student observes that on a hot, humid day, a cold can of soda quickly becomes covered in water droplets. What is the best explanation for this phenomenon?
- A. The soda is leaking through microscopic pores in the can.
- B. Water vapor molecules in the air transfer energy to the cold can, slow down, and condense into liquid.
- C. The cold temperature of the can causes oxygen and hydrogen in the air to combine and form water.
- D. The paint on the can reacts with the humidity to produce a thin layer of liquid.
10. During evaporation, a liquid turns into a gas. This phase change requires individual molecules to:
- A. lose kinetic energy.
- B. form stronger attractions.
- C. overcome molecular attractions.
- D. decrease their overall speed.