Thermal Basics
What is thermal energy?
The total kinetic energy of all particles in a substance.
What are the three main types of heat transfer?
Conduction, convection, and radiation.
When a metal spoon is placed in hot soup, the handle becomes warm. What happens to the spoon’s particles?
They move faster as they gain energy from the soup.
What does “kinetic energy” mean?
The energy of motion — how fast particles are moving.
Two cups of water are sitting on a table. One is cold, and one is warm. How do the molecules in the warm cup compare to the cold cup?
a) They’re the same.
b) They move slower.
c) They move faster.
d) They have more mass.
✅ c) They move faster.
What happens to molecular motion when temperature increases?
Molecules move faster.
Which type of heat transfer happens when you touch a metal spoon in hot soup?
Conduction.
On a cold morning, the air around a cup of hot cocoa feels warm. What happens to the air molecules near the cup?
They gain energy, move faster.
How is average kinetic energy related to temperature?
Higher temperature = higher average kinetic energy.
Malik took two identical metal rods—one was left in the shade, and the other was placed in direct sunlight. What is true about the molecules in the rod in sunlight?
a) They move faster.
b) They move slower.
c) They stop moving.
d) They change into different atoms.
✅ a) They move faster.
What is temperature a measure of?
The average kinetic energy of particles.
What type of heat transfer moves warm air up and cool air down in a room?
Convection.
You walk barefoot on hot pavement in the summer. What happens to the molecules in your foot when you step on the pavement?
They gain kinetic energy from the pavement and start moving faster.
If two objects have the same temperature, what does that tell you about their molecules' kinetic energy level?
Their molecules have the same average kinetic energy.
A cold can of soda is placed next to a warm sandwich. What happens to the molecules in each over time?
a) The soda molecules move faster; the sandwich molecules move slower until both reach the same temperature.
b) The soda molecules stop moving.
c) Only the sandwich molecules move.
d) The sandwich molecules freeze.
✅ a) The soda molecules move faster; the sandwich molecules move slower until both reach the same temperature.
What happens to thermal energy when two objects at different temperatures touch?
It transfers from the warmer to the cooler object.
How does radiation transfer heat?
Through electromagnetic waves — no contact or medium needed.
When sunlight heats the ground, the air just above it also warms up and begins to rise. What happens to the air molecules?
They gain energy, move faster.
A small cup of hot tea and a large pot of hot tea are at the same temperature. Which has more average kinetic energy?
They have the same average kinetic energy because temperature is the same.
Two metal blocks made of the same material are compared. One is 80°C and the other is 20°C. Which statement is true?
a) The cooler block’s molecules have more kinetic energy.
b) The hotter block’s molecules have more kinetic energy.
c) Both blocks’ molecules move at the same speed.
d) The hotter block’s molecules have less motion.
✅ b) The hotter block’s molecules have more kinetic energy.
What’s the difference between temperature and thermal energy?
Temperature measures average molecular motion; thermal energy measures total energy (depends on mass and temperature).
Why does metal feel colder than wood at the same temperature?
Metal conducts heat away from your hand faster than wood.
Lava from a volcano flows over cool rocks. As the rocks heat up, what is happening at the molecular level inside the rocks?
The molecules in the rocks gain thermal energy, move faster.
What is the difference between average kinetic energy and thermal energy?
Average kinetic energy measures the energy of individual molecular motion (temperature), while thermal energy measures the total energy of all molecules (depends on mass and temperature).
A scientist heats two identical samples of gas—Sample A from 10°C to 50°C, and Sample B from 10°C to 100°C. How do the gas molecules compare now?
a) Molecules in Sample A move faster than Sample B.
b) Molecules in Sample B move faster than Sample A.
c) The molecules are identical and move the same.
d) The molecules in Sample A stop moving.
✅ b) Molecules in Sample B move faster than Sample A.