AnswersDAEP-Science 7 A20 Day TermUnit Test

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To make a solution for an experiment, Gunther needs to add 40 g of a solute to 100 g of water. When making the solution at room temperature, he could only add 34 grams before the solute settled out.What could he do to dissolve the remaining 6 grams of the solute?

A
Put the solution in an ice bath, dissolve the solute, and let the solution return to room temperature.
B
Heat the solution, dissolve the solute, and let the solution cool verifying nothing settled out.
C
Add more water, boil the solution, and dissolve the solute until the some of the water evaporates.
D
Keep the solution at room temperature, add more water, and dissolve the excess solute.
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There are several different models that represent compounds. One type of model is shown.

Question illustration
A
a structural formula
B
a chemical formula
C
a space-filling model
D
a ball-and-stick model
23

Suppose that a substance in a beaker is heated over a burner in a science lab. Which observation would most likely indicate that a chemical change has occurred in the substance?

A
If the substance is a liquid or solid, an increase in temperature would indicate a chemical change.
B
If the substance is a liquid, a change of some of the liquid to gaseous form would indicate a chemical change.
C
If the substance is a solid, a change of some of the solid to liquid form would indicate a chemical change.
D
If the substance is a liquid or solid, production of an odor would indicate a chemical change.
24

Tijuan mixed a solid and a liquid together in a beaker. He determined that a chemical change occurred.

A
ice mixed into warm oil, because the change of state that occurred when the ice melted cannot be reversed
B
baking soda mixed into vinegar, because the production of bubbles indicates that a new substance formed
C
sugar mixed into hot water, because the disappearance of solid indicates that the chemical identity of the sugar changed
D
sand mixed into water, because when sand was added the mass of the beaker increased
25

Julie takes a cold glass of clear, colorless liquid out of the refrigerator and puts it on the table. As the liquid warms up to room temperature, Julie sees bubbles of gas form in the liquid and rise to the surface.Which conclusion is best supported by Julie’s observations?

A
The liquid is a pure substance because it is colorless.
B
The liquid is a mixture because its temperature rises.
C
The liquid is a pure substance because it remains liquid when cold.
D
The liquid is a mixture because it has a gas dissolved in a liquid.

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