Energy: Forms and Transfer — Answer Key
Part A: Fix the Sentence
Each sentence has an error. Rewrite it correctly on the line.
1. Fix the sentence:
A toaster only changes electrical energy into light energy.
Corrected: A toaster changes electrical energy mostly into heat energy.
Grade 4 students learn that a toaster turns electrical energy into thermal energy to brown the bread.
2. Fix the sentence:
A flashlight uses sound energy to light up the room.
Corrected: A flashlight uses electrical energy from batteries to make light energy.
In Grade 4 Science, batteries store chemical energy that becomes electrical energy and then light in a flashlight.
3. Fix the sentence:
A cell phone only uses electrical energy and gives off no other form.
Corrected: A cell phone uses electrical energy and gives off light, sound, and a little heat.
Grade 4 students learn that phones change electrical energy into several forms at the same time.
Part B: Fill in the Blank
Write the missing word or number on each line.
1. A lamp turns electrical energy into light and heat energy.
In Grade 4 Science, lamps give off both light and waste heat as the bulb glows.
2. A toy car with a wound-up spring has stored potential energy.
Grade 4 learners study how a spring stores potential energy that becomes motion when the toy is let go.
3. A speaker turns electrical energy into sound energy.
In Grade 4 Science, speakers use electrical signals to make their cones vibrate and produce sound.
4. A battery in a flashlight stores chemical energy until you turn it on.
Grade 4 students learn that batteries hold chemical energy that changes into electrical energy when used.
Part C: Short Answer
Answer each question in one or two complete sentences.
1. How does a hairdryer change one form of energy into two other forms?
Sample answer: A hairdryer plugs into the wall and uses electrical energy. Inside, the electricity makes a small motor spin, which is motion energy, and it also heats up a coil of wire, which gives off heat energy that warms the air blowing on your hair.
Grade 4 Science uses devices like hairdryers to show how one input of energy can split into several useful forms.
2. Pick a kitchen device and describe the energy changes that happen when it is turned on.
Sample answer: A blender uses electrical energy from the wall outlet. The electrical energy goes into a motor that turns the blades very fast, which is motion energy. The spinning blades also make sound energy and a little heat as they cut through the food inside.
Grade 4 students practice tracing energy from the source through the device to several output forms.