7th grade Unit 4 Review - Energy Transformations and Heat Flow

Energy transformations occur when...

• energy is created through conduction

• energy changes from one form to another

• two forces slide together that are touching

• a chemical reaction takes place

Answer explanation

Energy transformations occur when energy changes from one form to another, such as from kinetic to potential energy. This is the fundamental principle of energy conservation and transformation.

Tags

NGSS.MS-PS3-5

NGSS.MS-PS3-3

Which energy conversion is taking place when you put gasoline in a car?

• thermal -> electrical

• mechanical -> electrical

• chemical -> mechanical

• mechanical -> electromagnetic

Answer explanation

When you put gasoline in a car, the chemical energy stored in the gasoline is converted into mechanical energy, which powers the engine and moves the vehicle. Thus, the correct conversion is chemical -> mechanical.

Tags

NGSS.HS-PS3-3

NGSS.HS-PS1-4

Which of the following shows the correct order of the energy transformations that occur when green plants produce their food from the Sun’s energy?

• chemical to thermal

• light to chemical

• thermal to light

• chemical to electrical

Answer explanation

Green plants convert sunlight (light energy) into chemical energy through photosynthesis. This process transforms light energy into chemical energy stored in glucose, making 'light to chemical' the correct order of energy transformations.

Tags

NGSS.MS-LS1-6

NGSS.MS-LS2-3

Which of the following energy transformations occur when a lamp that is plugged into a wall socket is functioning correctly?

• Chemical to light

• Electrical to chemical

• Electrical to light

• Chemical to electrical

Answer explanation

When a lamp is functioning, it transforms electrical energy from the wall socket into light energy. Therefore, the correct transformation is electrical to light, as the lamp converts electrical energy into visible light.

Which of the following shows an energy transformation from chemical energy to electrical to light energy?

• A bolt of lightning lights the night sky.

• A candle glows brightly in the dark.

• A fire in a fireplace lights up a room.

• A battery causes a flashlight to shine.

Answer explanation

A battery stores chemical energy, which is transformed into electrical energy when used. This electrical energy powers the flashlight, producing light energy. Thus, the correct choice is 'A battery causes a flashlight to shine.'

What energy transformations take place when a battery-operated radio is in use?

• Electrical to chemical to light

• Sound to chemical to mechanical

• Chemical to electrical to sound

• Light to electrical to thermal

Answer explanation

When a battery-operated radio is used, it transforms chemical energy from the battery into electrical energy, which then powers the radio to produce sound. Thus, the correct sequence is chemical to electrical to sound.

People get energy from the food that they eat and transform that energy as they move. Which energy transformations occur as a student rapidly rubs the palms of his hands together?

• mechanical to thermal to electrical

• chemical to mechanical to thermal

• mechanical to chemical to sound

• chemical to sound to electrical

Answer explanation

As the student rubs his hands, chemical energy from food is converted into mechanical energy through movement, which then transforms into thermal energy due to friction, making 'chemical to mechanical to thermal' the correct choice.

Tags

NGSS.MS-PS3-5

Which of the following devices transforms electrical energy into mechanical energy?

• An e-reader

• a fan

• a manual pencil sharpener

• ipod

Answer explanation

A fan transforms electrical energy into mechanical energy by using an electric motor to create motion, making it the correct choice. The other options do not perform this function.

Energy transformations occur when...

• energy is created through conduction

• energy changes from one form to another

• two forces slide together that are touching

• a chemical reaction takes place

Answer explanation

Energy transformations occur when energy changes from one form to another, such as from kinetic to potential energy. This is the fundamental principle of energy conservation, unlike the other options which do not accurately describe this process.

Tags

NGSS.MS-PS3-4

NGSS.MS-PS3-5

NGSS.MS-PS3-3

A teacher rubbed a match against a piece of sandpaper. The match started to burn. Which statement best describes the energy changes that occurred?

• The chemical energy stored in the match changed to thermal energy and light energy.

• The thermal energy stored in the match changed to light energy and chemical energy.

• The light energy and thermal energy stored in the match changed to mechanical energy.

• The light energy and thermal energy stored in the match changed to chemical energy.

Answer explanation

The correct choice states that the chemical energy in the match converts to thermal energy and light energy when it burns. This accurately describes the process of combustion, where stored chemical energy is released as heat and light.

Tags

NGSS.MS-PS3-5

NGSS.MS-PS1-2