P. 5.5 Physical and chemical changes test

A group of students weighed a sealed jar full of heavy cream. Then they shook the jar until the cream separated, and then they weighed the jar again. Which of the following would BEST describe its weight?

• The jar will have gained weight because some liquid changed to a solid.

• The jar will have gained weight because shaking added energy to it.

• The jar will have lost weight because of friction from shaking the liquid.

• The jar will have kept the same weight because it did not gain or lose any matter.

Cherise mixed 30 grams of sugar into 100 grams of water. The sugar dissolved. Find the mass of the sugar solution.

Water Mass 100 grams Volume 100 mL

Sugar Mass 30 grams Volume 15 mL

sugar solution Mass ? Volume 108 mL

• 100 grams

• 108 grams

• 130 grams

• 200 grams

Julia is following a recipe to make batter for a cake. She uses a scale to weigh each ingredient separately. Julia can BEST use this information to predict the weight of the mixed batter by

• adding the weights of each ingredient together.

• multiplying the weights of each ingredient together.

• dividing the weight of the wet ingredients from the weight of the dry ingredients.

• subtracting the weight of the wet ingredients from the weight of the dry ingredients.

A jeweler melts gold to make jewelry. As the gold melts, the mass

• increases

• decreases

• is destroyed

• stays the same

Tracy measured the mass of an empty beaker. The mass of the beaker was 100 grams (g). She filled the beaker with some water and measured the mass again. The total mass was 150 grams. Tracy put the beaker with water in the freezer. After the water froze, what was the mass of the beaker?

• 50 g

• 100 g

• 150 g

• 500 g

Students took some ice cubes out of the freezer at 1:00 p.m. An hour later, they observed how the ice cubes had changed. The change is BEST described as

• chemical because a liquid formed.

• physical because it happened over time.

• physical because no new substance was formed.

• chemical because heat caused the change.

When sugar in a beaker is heated over a low flame, the solid crystals disappear and a thick, yellow-brown liquid forms. Determine whether this change is a chemical reaction or a physical change.

• chemical reaction

• physical change

Several milliliters of water were added slowly to a container holding liquid nitrogen at a temperature of –96°C. Large bubbles formed in the mixture, and the volume of the mixture decreased. After the mixture stopped bubbling, a solid had formed the bottom of the container. When the solid was isolated, it floated in water and melted at 0°C. Based on these observations, determine whether a chemical reaction occurred.

• A chemical reaction did not occur

• a chemical reaction did occur

A student bends a piece of wire. Which of these BEST describes why bending the wire is an example of a physical change?

• because the bent wire is a more useful tool

• because the bent wire is a new material

• because the bent wire will break into two pieces

• because the bent wire can be straightened again

Manuel was having trouble opening a new glass jar of pickles. His father told Manuel to hold the metal lid of the jar under running hot water for a few seconds, then try again. Then the lid opened easily. What is the MOST likely reason Manuel’s father suggested using hot water to loosen the lid?

• Glass contracts when it is heated.

• Metals expand when they are heated.

• Metals are easier to grip when they are warm.

• Hot water reduces friction between metal and glass