Changes in Matter Review

Multiple Choice

Jia is preparing to cook a family dinner, and she begins by gathering ingredients for the main course and dessert. She realizes that most ingredients go through both physical and chemical changes as they cook.

One of the ingredients for her main course undergoes physical changes. Which of the following is a physical change?

• cooking eggs

• grilling hamburger

• baking bread

• boiling water

Explanation

The correct answer is “boiling water.” Boiling water is a physical change, because the water does not become a new substance when it is boiled. It remains water, only at a higher temperature. However, when cooking eggs, grilling a hamburger, and baking bread, each go through a chemical change to become a new substance. The heat from cooking the egg and hamburger change the protein permanently. Baked bread involves yeast, which causes a chemical change in the dough.

Multiple Choice

Jia is preparing to cook a family dinner, and she begins by gathering ingredients for the main course and dessert. She realizes that most ingredients go through both physical and chemical changes as they cook.

For dessert, she prepares to bake a delicious apple pie. During one of the steps, she notices an example of a chemical change. Which one is it?

• softening butter

• folding a sheet of aluminum foil

• heating sugar to make caramel

• dicing an apple

Multiple Choice

Jia is preparing to cook a family dinner, and she begins by gathering ingredients for the main course and dessert. She realizes that most ingredients go through both physical and chemical changes as they cook.

As her family eats the delicious dinner, Jia remembers an important fact about the law of conservation of mass. What does she remember?

• Matter always moves from hot to cold.

• Matter is not created or destroyed in any change.

• Matter can change physically or chemically.

• Matter is the amount of mass in a given volume.

Explanation

The correct answer is “Matter is not created or destroyed in any change.” The law of conservation of mass states that no mass is lost or gained during a physical or chemical change. "Matter always moves from hot to cold" applies to the movement of thermal energy. "Matter can change physically or chemically" is not a law of conservation of mass, but a statement of fact. "Matter is the amount of mass in a given volume" is the definition of density.

Explanation Slide...

The correct answer is “heating sugar to make caramel.” When sugar is heated, it goes through a chemical change because it breaks down into different substances. As you cook sugar, it changes both color and taste. It turns into another substance called caramelin. Chemical changes cannot be reversed. Softening butter, folding foil, and dicing an apple are all physical changes, because none of them are turning into new substances. Softened butter is still butter. Folded aluminum foil and dicing apples changes the shape of the original substance, but nothing new is formed.

Fill in the Blank

Fill in words that correctly complete this sentence.

Anna looks around the skating rink and notices many examples of the movement of thermal energy. For example, she sees her friend holding a cup of hot chocolate in the cold rink. Thermal energy flows from ________ matter to cold matter.

Explanation Slide...

You notice the flow of thermal energy when you are swimming in cold waters. The warmth from your body flows out to the cold water. Also, when a cold drink sits in a warm room, the warmth of the room flows in to the cold drink.

Multiple Choice

George is writing a newspaper article about the fire at the town library. His introductory paragraph has an example of conservation of mass. Which of these sentences illustrates conservation of mass?

• Our town library dealt with a terrible fire in one of its rooms over the weekend.

• The room contained much-loved books and magazines.

• Firefighters rushed to the scene, but were too late.

• All that remained of the books and magazines were ash, water vapor, and carbon dioxide fumes.

• The mayor arrived soon afterward and urged everyone to donate to help rebuild this important community building.

Explanation Slide...

The correct answer is “All that remained of the books and magazines were ash, water vapor, and carbon dioxide fumes.” The sentence lists the products of the combustion reaction, including water vapor and carbon dioxide, which are not visible, but do have mass.

Open Ended

Patrick is giving a presentation on thermal energy to his class. He knows some reactions require thermal energy to occur and others produce thermal energy during the reaction. Name and provide an example of each type of reaction.