Particles
What type of energy is the energy of motion?
Kinetic energy
In which state are particles packed closely together and mainly vibrate in place?
Solid
What are the three main ways thermal energy can be transferred?
Conduction, Convection, Radiation
You touch a hot mug and your hand becomes warm.
Conduction
A sample is heated from 20°C to 35°C. What happened to the average kinetic energy of its particles?
The average kinetic energy increased because the temperature increased.
What happens to particle motion when a substance gains thermal energy and its temperature increases?
Particles move faster
In which state can particles move or slide past one another while remaining relatively close together?
Liquid
Thermal energy naturally moves from an object with a ______ temperature to an object with a ______ temperature.
Higher/warmer lower/cooler
Warm air rises above a heater.
Convection
A student tests three materials around a warm container. Which material allowed the greatest amount of thermal energy to leave the container?
Starting temp Final temp
Foam 60°C 48°C
Metal 60°C 34°C
Cotton 60°C 43°C
Metal
Which usually has greater average kinetic energy: particles at 20°C or particles of the same substance at 80°C?
80°C
Which state generally has particles moving rapidly and far apart?
Gas
What is an insulator?
A material that slows the transfer of thermal energy.
You feel warmth from the Sun on your face
Radiation
Two identical samples begin at 25°C. Sample A is heated to 40°C and Sample B is heated to 65°C. Which sample experienced the greater increase in average kinetic energy?
Sample B
A substance is cooled. What happens to the average kinetic energy of its particles?
It decreases
As a liquid gains enough thermal energy to become a gas, what happens to particle motion and spacing?
Particles move faster and spread farther apart.
Students put 80°C water into two containers. After 20 minutes, Container A is 74°C and Container B is 57°C. Which container reduced thermal energy transfer more?
Container A
A metal spoon is left in hot soup, and the handle becomes warm.
Conduction
A student wants to reduce thermal energy transfer through the wall of a model shelter. Should the student choose a good conductor or a good insulator? Explain.
A good insulator because it slows thermal energy transfer.
A student says, “Particles get bigger when a substance is heated.” Explain what actually happens.
The particles do not get bigger. Their average motion increases, and particle spacing may change.
A gas is cooled until it becomes a liquid and eventually a solid. Describe what happens to its particles.
The particles lose kinetic energy, move more slowly, and become more closely packed.
Why does insulation help a container keep hot food warm longer?
It slows/reduces the transfer of thermal energy from the warmer food to the cooler surroundings.
Air near a heater warms, rises, cools, and then sinks. What type of thermal-energy transfer creates this circulation?
Look at the data: Which is the best insulator.
Starting temp Final temp
Material A 70°C 62°C
Material B 70°C 48°C
Material C 70°C 65°C
Material C