Chapter 7: Forms of Energy

Jean and Larry are comparing the energy released by three objects: an electric oven, a glow stick, and the Sun. Which statement could be a conclusion of their comparison?

• Energy can be transferred from one object to another, but it does not change form.

• Objects may release one form of energy but not two or more forms at the same time.

• Heat and light travel in waves through matter, but they do not travel through empty space.

• Heat and light are forms of energy that may travel through matter or empty space.

Janice’s scout troop is camping in the woods. Today, the scouts are collecting wood sticks for a craft project. Janice claims that a sample of wood always contains energy, regardless of its motion or position. How can the scouts support Janice’s claim?

• Shine a light on a wood stick.

• Strike a wood stick and listen to the sound it makes.

• Burn a wood stick in a campfire.

• Roll the wood stick across a grassy slope.

George and Babi want to use a small rubber ball to demonstrate mechanical energy. Which action would show that a rubber ball can gain mechanical energy and then use that energy to cause motion?

• Roll the ball across a smooth floor and observe it roll to a stop.

• Puncture the rubber and then squeeze the air out of the ball.

• Toss the ball against a wall and observe it bounce back.

• Lift the ball from the ground and then drop it into a sandbox.

Mandy observes a slice of bread before and after it enters a toaster. Which action caused the changes to the bread?

• A. Electrical energy the bread received from the toaster.

• B. Thermal energy the bread received from the toaster.

• C. Thermal energy the bread lost to the toaster.

• D. Light energy the bread received from the toaster.

Brie and Ellen are investigating how electrical energy is changed in several devices. They find one device that is useful because it combines heat and the energy of motion. Which of these could be this device?

• a cell phone

• a robot vacuum cleaner

• an electric oven

• an electric hair dryer

Chloe’s team is investigating the flow of electrical energy in a circuit. They assemble the materials as shown in the diagram. Which sentence best explains the flow of electrical energy in the circuit?

• A. Electrical energy is flowing in a complete circuit between the battery and bulb.

• B. Electrical energy is flowing from the battery to the light bulb in both paths.

• C. Electrical energy is not flowing because the negative terminal of the battery is not included in the path.

• D. Electrical energy is not flowing because the circuit has one extra wire.

Ty and Wee-Chin are investigating electrical charges. During their investigation, they observe two balloons in the position shown in the diagram. The balloons remained in this position for several minutes. How could the students have prepared the two balloons that they observed?

• They rubbed both balloons on a carpet so that both balloons gained the same electrical charge.

• They filled two balloons with water so that both balloons gained the same electrical charge.

• They rubbed the balloons with different materials so that both balloons gained opposite charges.

• They pushed or pulled the balloons so that they gained mechanical energy.

With the teacher’s permission, Jorge slices open one of the electrical wires from a science kit. Jorge observes a copper core that is surrounded by rubber. Which statement explains the purpose of using two materials – copper and rubber – in the wire?

• The materials allow electric current to flow along the outside of the wire.

• The materials work together like a switch to stop and start the flow of electric current.

• The materials allow electric current to flow through all parts of the wire.

• The materials keep electric current flowing through the wire and not leaking out.