Q: A balloon filled with helium gas is set free and starts to move upward. Which of the following best explains why the helium balloon moves upward? OPTIONS:
- The density of helium is less than the density of air.
- The air resistance lifts the balloon up.
- There is no gravity acting on the helium balloons.
- The wind blows the balloon upward.
A: The density of helium is less than the density of air.

Air is made up of many gases. Which gas is found in the greatest amount?
OPTIONS:
- Nitrogen
- Oxygen
- Carbon dioxide
- Hydrogen

Nitrogen

Q: Which type of energy in gasoline is transformed into mechanical energy in a motorcycle engine? ---- OPTIONS:
- chemical
- nuclear
- magnetic
- electrical

A: chemical

Base your answer on the information below and on your knowledge of science. A baseball strikes the roof of a car and dents it. The paint on the roof begins to crack and chip, exposing the metal. The exposed metal on the roof rusts, eventually causing a small hole in the roof. Which event is a chemical change?
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OPTIONS:
- The baseball strikes the roof.
- The roof of the car dents.
- The paint cracks and chips.
- The exposed metal rusts.

The exposed metal rusts.

Question:
Which group of organisms can show significant trait changes in the shortest period of time?
OPTIONS:
- bacteria
- birds
- fish
- reptiles
Answer:
bacteria

*Question*: Many areas of Massachusetts have small deep ponds called kettle ponds. Which of the following best explains the formation of these ponds? OPTIONS:
- avalanche
- wind erosion
- glacial depression
- sediment deposition
*Answer*:
glacial depression