Chemical Interactions 7-8 review

In which substance(s) did the particles speed up?

• Only the butter

• The butter and the cheese, but not the wax

• All of the substances

• None of the substaces

The melting/freezing point of mercury is -39 degrees Celcius. A scientist put liquid mercury into a freezer that is kept at a constant temperature of -35 degrees Celcius. Will the liquid mercury freeze? (mark the one best answer)

• No, because there is not enough energy in the freezer to freeze the mercury.

• Yes, because the particles will slow down enough for the mercury to freeze.

• No, because the freezer isn't cold enough to freeze mercury.

• Yes, because the freezer is cold enough to freeze mercury.

A student dissolved 20g of salt in a cup of water. She left the cup uncovered in an area where nobody could touch it. When she returned to the cup 10 days later, she found that all the water was gone, and there were crystals in the bottom of the cup. What is the best conclusion, based on her observations?

• The water and some salt evaporated, but some salt is left in the cup.

• There was a chemical reaction, and a new solid was left behind.

• The water evaporated, and there is 20g of salt in the cup.

• The water and salt separated and then the water evaporated, but there is no way to know what is left in the cup.

True or false: Dissolving does not require two substances.

• True

• False

True or false: Melting does not require a change in kinetic energy.

• True

• False

True or false: Dissolving is a phase change.

• True

• False

True or false: Neither melting nor dissolving require a chemical reaction to occur.

• True

• False

A student hangs a wet T-shirt on a clothesline. A few hours later, the T-shirt is dry. What happens to the water particles as the T-shirt dries? (mark the one best answer)

• The water particles are absorbed by the T-shirt.

• The water particles evaporate, forming a cloud.

• The water particles disappear and no longer exist.

• The water particles move faster and become part of the air.

A student mixed together two substances that were at room temperature. The container quickly began to feel colder in the student's hand. Please check all the boxes of answers that are true.

• Energy transferred from the student's hand to the container.

• Energy was absorbed by the mixture.

• Cold was released from the mixture.

• The hand-and-container system is at equilibrium.

The substance being dissolved is called the ________

• solvent

• solid

• solute

• solvate