Thermal Energy
What is thermal energy?
Thermal energy is the energy of moving particles in an object.
What happens to particles when an object is heated?
speed up, bounce of one another and become less dense
Why does a hot drink cool down when you leave it sitting on a table?
The hot drink cools because thermal energy moves from the warm drink to the cooler air and table... convection
What happens to warm air?
It rises
Heat moving by touching is called what?
Conduction
What happens to thermal energy when an object is heated?
When an object is heated, its thermal energy increases.
How does particle motion change when an object cools down?
They slow down and become more dense
Hot air moving around a room which type?
Convection
Why does cold air sink?
It is denser than warm air.
A pot heating up on a stove which type?
Conduction
Explain the reasoning as to why an ice cube melts in your hand using the rules of thermal energy
Heat flows from hot to cold... Conduction
Why does air inside a tire expand on a hot day?
Air particles move faster and spread out on a hot day, causing the tire to expand.
Why does cold air sink?
It is denser than warm air.
X-rays are used in hospitals to see inside the human body. Explain why x-rays are considered a form of radiation and not conduction or convection.
X-rays are radiation because they transfer energy through waves and do not require direct contact or moving particles.
Why can you feel heat from a fire without touching it? (One word)
Radiation.
Which type of thermal energy transfer can occur in a vacuum (empty space)
radiation.
Define what a convection current is and explain how it works using a real-world example.
A convection current is the movement of a liquid or gas caused by heating and cooling. Warm, less dense fluid rises while cooler, more dense fluid sinks, creating a cycle.
Example: In boiling water, hot water rises and cool water sinks, spreading heat throughout the pot.
How does the Sun heat the Earth?
Radiation
A blacktop parking lot feels much hotter than grass on a sunny day. Why?
The blacktop absorbs more radiation from the Sun than grass.
Why does touching a cold desk feel cold even though it’s room temperature?
Heat moves from your hand to the desk by conduction.
A metal spoon and a plastic spoon are placed in the same cup of hot water. After one minute, the metal spoon feels hotter. Explain why this happens using thermal energy transfer.
Metal transfers thermal energy faster than plastic because it is a better conductor, so more thermal energy moves into the metal spoon.
Explain how the motion of particles changes as thermal energy moves from a hot object to a cold object.
Faster-moving particles in the hot object collide with slower-moving particles in the cold object, transferring energy and causing the cold particles to speed up.
A lava lamp works by heating and cooling liquid inside it. Explain how density changes cause the liquid to rise and sink.
When the liquid is heated, it becomes less dense and rises. As it cools, it becomes more dense and sinks, creating a continuous convection cycle.
Explain how boiling water shows convection.
Hot water rises, cool water sinks, creating a cycle.
A car is parked in the Sun with the windows closed. Explain how all three types of thermal energy transfer cause the inside of the car to heat up.
Radiation from the Sun enters the car, conduction transfers heat through the car’s materials, and convection circulates warm air inside the car.