Energy Transfer
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84 Terms
What is energy?
Energy is the ability to cause change or do work.
Where does most energy on Earth come from?
The Sun.
What are particles?
Tiny pieces that make up matter.
How are particles arranged in a solid?
They are packed closely together and vibrate in fixed positions.
How are particles arranged in a liquid?
They are close together but can move past each other.
How are particles arranged in a gas?
They are far apart and move freely.
What happens to particles when they are heated?
They gain kinetic energy, move faster and usually spread further apart.
What is temperature?
A measure of the average kinetic energy of particles.
What is heat?
The transfer of thermal energy from a hotter object to a colder object.
Which direction does heat transfer?
From hot → cold.
What unit is heat measured in?
Joules (J).
How many joules are in 1 kJ?
1000 J.
What are the three methods of heat transfer?
Conduction, convection and radiation.
What is conduction?
Heat transfer through direct contact and collisions between particles.
Where does conduction mainly occur?
In solids.
Why are metals good conductors of heat?
They contain free-moving electrons that can transfer energy quickly through the metal.
What is an insulator?
A material that is a poor conductor of heat.
Give examples of insulators.
Air, wood, plastic, rubber and wool.
Why is air a good insulator?
Air particles are far apart, so thermal energy is not transferred easily between them.
What is convection?
Heat transfer caused by the movement of a fluid.
What are fluids?
Liquids and gases.
Where does convection occur?
In liquids and gases.
Why does warm air rise?
Heating makes the particles move faster and spread out, making the air less dense.
Why does cool air sink?
Cool air is denser than warm air, so it sinks.
What is a convection current?
A circulating movement where warm fluid rises and cool fluid sinks.
What is density?
How much matter is packed into a given space.
How does particle spacing affect density?
Particles packed closer together usually make a substance more dense.
What is radiation?
Heat transfer by electromagnetic waves.
Does radiation need particles to travel?
No.
Can radiation travel through a vacuum?
Yes.
How does heat from the Sun reach Earth?
Through radiation.
What type of radiation is mainly involved in thermal radiation?
Infrared (IR).
How fast does light travel?
300,000,000 m/s
What can happen when infrared radiation reaches a surface?
It can be transmitted, absorbed or reflected.
What does absorption mean?
The radiation is taken in by the object.
What does reflection mean?
The radiation bounces off the surface.
What does transmission mean?
The radiation passes through the material.
Which surfaces are good absorbers of thermal radiation?
Dark, dull surfaces.
Which surfaces are good reflectors of thermal radiation?
Light, shiny surfaces.
Which surfaces are good emitters of thermal radiation?
Dark, dull surfaces.
Which surfaces are poor emitters?
Light, shiny surfaces.
Why are good absorbers usually good emitters?
Surfaces that absorb thermal radiation well generally emit thermal radiation well too.
What is sound?
Sound is energy transferred through vibrations in a medium.
What produces sound?
A vibrating object.
How does sound travel?
Vibrations are passed from one particle to the next.
What does sound need to travel?
A medium containing particles.
Why can't sound travel through a vacuum?
A vacuum has no particles to pass the vibrations along.
What type of wave is sound?
A mechanical wave.
What is a mechanical wave?
A wave that transfers energy through matter using particle vibrations.
What is an electromagnetic wave?
A wave that transfers energy and does not require a medium.
What is a transverse wave?
A wave where particles move perpendicular to the direction of wave motion.
What is a longitudinal wave?
A wave where particles move parallel to the direction of wave motion.
What is a compression?
A region where particles are close together.
What is a rarefaction?
A region where particles are spread apart.
What is amplitude?
The maximum height of a wave from its resting position.
What does amplitude affect in sound?
Loudness.
What happens when amplitude increases?
The sound becomes louder.
What happens when amplitude decreases?
The sound becomes quieter.
What is frequency?
The number of vibrations or waves passing a point each second.
What is frequency measured in?
Hertz (Hz).
What does frequency affect in sound?
Pitch.
What happens when frequency increases?
The pitch becomes higher.
What happens when frequency decreases?
The pitch becomes lower.
What is wavelength?
The distance between matching points on consecutive waves.
How are frequency and wavelength related when wave speed stays constant?
Higher frequency means a shorter wavelength; lower frequency means a longer wavelength.
How does sound speed compare in solids, liquids and gases?
Sound generally travels fastest through solids, then liquids, then gases.
Why does sound travel faster through solids?
Solid particles are close together, so vibrations can be transferred between them quickly.
Out of steal, water, air, and brick, which one dose sound travel the fastest through?
Steal
What is the speed of sound in water?
1500 m/s.
What is the speed of sound in air?
330 m/s.
Which is louder: a high-amplitude or low-amplitude sound?
High-amplitude.
Which has the higher pitch: high-frequency or low-frequency sound?
High-frequency.
A sound is loud and high-pitched. What does this mean for its waves?
It has high amplitude and high frequency. If the speed stays constant, it also has a shorter wavelength.
What happens during a change of state?
Particles gain or lose energy, changing their movement and spacing.
Why does a substance usually expand when heated?
Particles move faster and spread further apart.
How do convection currents help heat a room?
Warm air rises and cool air sinks, creating a circulating current that transfers thermal energy around the room.
How does a cup of tea lose heat?
Through conduction, convection and radiation.
Why do dark surfaces heat up more easily?
They absorb more thermal radiation.
Why are shiny surfaces useful for reducing heat transfer by radiation?
They reflect more thermal radiation.
What is the difference between heat and temperature?
Temperature measures the average kinetic energy of particles; heat is thermal energy being transferred.
What is the key difference between sound and radiation waves?
Sound is a mechanical wave and needs a medium; radiation is electromagnetic and can travel through a vacuum.
What would happen to a sound wave if its amplitude increased but frequency stayed the same?
It would become louder but keep the same pitch.
What would happen to a sound wave if its frequency increased but amplitude stayed the same?
It would have a higher pitch but the same loudness.