Science Grade 7: Thermal Energy Unit Exam Review

What is thermal equilibrium?

• When all substances in a system have different temperatures

• When all substances in a system reach the same temperature

• When heat stops moving

• When only one substance in a system changes temperature

Answer explanation

Thermal equilibrium occurs when all substances in a system reach the same temperature, meaning there is no net heat transfer between them. This is the correct choice, as it defines the state of balance in temperature.

How does thermal energy move in a predictable pattern?

• From cooler to warmer areas

• From warmer to cooler areas

• In random directions

• It does not move

Answer explanation

Thermal energy moves from warmer to cooler areas due to the second law of thermodynamics, which states that heat naturally flows in this direction until thermal equilibrium is reached.

Tags

NGSS.MS-PS1-4

Which method of heat transfer does not require a medium?

• Conduction

• Convection

• Radiation

• Conduction and convection

Answer explanation

Radiation is the only method of heat transfer that does not require a medium, as it can occur through the vacuum of space. In contrast, conduction and convection require materials to transfer heat.

What happens to the kinetic energy of particles as the temperature of a substance increases?

• It decreases

• It remains the same

• It increases

• It fluctuates randomly

Answer explanation

As the temperature of a substance increases, the kinetic energy of its particles also increases. This is because higher temperatures provide more energy, causing particles to move faster.

Tags

NGSS.MS-PS1-4

NGSS.MS-PS3-4

In which scenario is conduction the primary method of heat transfer?

• Heating water in a pot

• A microwave oven cooking food

• A metal rod being heated at one end

• Warm air rising in a room

Answer explanation

Conduction is the primary method of heat transfer when heat moves through a solid material. In this case, a metal rod being heated at one end transfers heat along its length through direct contact between particles.

What is the primary method of heat transfer in fluids?

• Conduction

• Convection

• Radiation

• Insulation

Answer explanation

The primary method of heat transfer in fluids is convection, which involves the movement of fluid itself to transfer heat. In contrast, conduction occurs in solids, and radiation does not require a medium.

Which of the following is an example of radiation?

• Heat from a stove warming a pot

• Heat from the sun warming your skin

• Heat traveling through a metal rod

• Heat circulating in a room

Answer explanation

Heat from the sun warming your skin is an example of radiation, as it involves the transfer of energy through electromagnetic waves. The other options describe conduction or convection, not radiation.

Tags

NGSS.MS-PS4-2

Which of the following is an example of thermal energy in everyday life?

• A car engine running

• A book on a shelf

• A light bulb turned off

• A cold drink in a refrigerator

Answer explanation

A car engine running is an example of thermal energy because it generates heat as fuel is burned to produce motion. In contrast, a book, a turned-off light bulb, and a cold drink do not actively produce thermal energy.

Tags

NGSS.MS-PS1-4

Which of the following is an example of conduction in solids?

• Warm air rising from a heater

• A metal spoon getting hot from a boiling pot

• Sunlight warming the Earth's surface

• Water boiling in a pot

Answer explanation

Conduction is the transfer of heat through direct contact. A metal spoon getting hot from a boiling pot is a clear example, as heat moves from the hot pot to the spoon through direct contact.

What effect does increasing temperature have on most materials?

• They contract

• They expand

• They remain unchanged

• They become denser

Answer explanation

Increasing temperature causes most materials to expand due to increased molecular motion. This expansion is a common physical property observed in solids, liquids, and gases, making 'They expand' the correct choice.

Tags

NGSS.MS-PS1-4

NGSS.MS-PS3-4