EXPANSION
What happens to most materials when they are heated?
They expand.
What usually happens to matter when it cools?
It contracts
Can you feel heat from a heat lamp without touching it? Why?
Yes, because heat travels through radiation.
What is conduction?
The transfer of thermal energy(heat) through direct contact.
What is convection?
Heat transfer through the movement of liquids or gases.
What happens to the particles of a material when it is heated?
They move faster and usually spread farther apart
What happens to the movement of particles when a substance cools?
The particles move more slowly
Does radiation require direct contact between objects?
No
Which type of material is generally a better conductor of heat: metal or wood?
Metal
Which two states of matter commonly transfer heat through convection?
Liquids and gases
Why are small gaps left between sections of railroad tracks?
To allow the metal to expand when heated
A metal lid becomes easier to remove after cold water is poured over it. Why? Explain
The metal lid cools and contracts slightly
What type of energy waves transfer heat through radiation?
Electromagnetic waves
A metal spoon is left in a cup of hot tea. Why does the handle become warm?
Heat travels through the spoon by conduction.
When water is heated in a pot, why does the warmer water rise?
It becomes less dense than the cooler surrounding water.
Why does a balloon expand when the air inside it is heated?
The air particles move faster and spread out, causing the balloon to expand.
What happens to the length of a metal wire when its temperature decreases?
It usually becomes shorter due to contraction
Why does wearing a black shirt on a sunny day often make you feel hotter than wearing a white shirt?
Black absorbs more of the Sun’s radiation, while white reflects more of it.
In which direction does thermal energy flow when a hot object touches a cold object?
From the hotter object to the colder object
How do convection currents help warm an entire pot of water? Explain
Warm water rises and cooler water sinks, creating circulation that transfers heat.
Why does a liquid in a thermometer rise when its temperature increases?
The liquid expands as it is heated, increasing its volume.
Explain why overhead power lines may sag more on hot days than on cold days.
The metal wires expand when heated and contract when cooled
Why can radiation transfer heat through the vacuum of space, while conduction and convection cannot?
Radiation travels through waves and does not require matter.
Why are cooking pot handles often made of plastic or wood instead of metal?
Plastic and wood are poor conductors of heat, helping keep the handles cooler.
Why does smoke from a fire rise into the air instead of staying close to the ground?
The hot air and gases from the fire are less dense than the surrounding cooler air, so they rise through convection.