7th Science Final

Anh measured the temperature of a pond near his house. Before he left for school, the water in the pond was 18°C. When he came home from school, the temperature of the pond was higher than it was in the morning. What happened to the water molecules while he was at school?

• The molecules got closer together.

• The molecules started moving faster.

• The water lost cold molecules.

• The molecules became larger.

Scientists digging in a cave found an unknown substance. The scientists found that the substance’s molecules were moving around each other. The scientists increased the speed of the substance’s molecules and caused a phase change. How did the scientists do this, and how did this affect the substance?

• The scientists transferred energy INTO the substance, and the substance changed into a gas.

• The scientists transferred energy INTO the substance, and the substance changed into a liquid.

• The scientists transferred energy OUT OF the substance, and the substance changed into a solid.

• The scientists transferred energy OUT OF the substance, and the substance changed into a liquid.

Of the following, which is the best description of the freedom of movement in liquids?

• molecules only move in place, not around each other

• molecules move around, not away from each other

• molecules move away from each other

• molecules are charged and move away from each other

When a lot of energy is added INTO a liquid substance, but the substance does not change phase, that means ...

• the molecular attraction was stronger than the amount of energy transferred in

• the molecular attraction of a substance changed

• the molecular attraction was weaker than the amount of energy transferred in

• different substances can have weaker or stronger molecular attraction

Which statement is true about the molecule model shown?

• Model B represents a solid with the most thermal and kinetic energy.

• Model C represents a gas with the most thermal and kinetic energy.

• Model A represents a solid with the least thermal and kinetic energy.

• Model B represents a liquid with a medium amount of thermal and kinetic energy.

When a substance goes from a liquid to a solid, it is ...

• melting

• freezing

• evaporating

• condensing

a pull between two molecules that is always the same for a substance

• molecular attraction
• condensation
• evaporation
• freedom of movement

What two processes occur when energy is taken out of a substance?

• freezing

• melting

• condensation

• evaporation

Lily is doing a science experiment with a substance in a sealed jar. At first, the substance’s molecules are moving around each other. What will happen to Lily’s substance if she transfers energy into the substance and causes a phase change?

After the phase change, the substance’s molecules will move . . .

• faster, and the substance will be a liquid.

• faster, and the substance will be a gas.

• slower, and the substance will be a solid.

• slower, and the substance will be a liquid.

A population of panthers lives in the southeastern United States. Over 50 years, the size of the panther population in the region increased. What best explains the increase in the size of the panther population?

• The panther population is always increasing because no animal eats panthers.

• Fewer panthers were born than died.

• More panthers were born than died.

• A lot of panthers were born and none of them died.