10 minutes maximum! Can you do it in 5?

 1. Conduction is a method of heat transfer between the particles in a substance. In which state of matter is conduction least effective?

  • A. Solid
  • B. Liquid
  • C. Gas
  • D. All three states of matter are equal

2. Metals are very good conductors of heat. Why is this?

  • A. Particles are close together
  • B. High kinetic energy of particles
  • C. Particles have weak bonds between them allowing freedom of movement
  • D. Large numbers of free electrons

3. The Diagram shows three blocks P, Q and R in thermal contact. P is denser than the other two blocks which are identical. All are at the same high temperature.

3 blocks in thermal contact

  

3. In which directions does heat energy flow by conduction between the blocks?

  • A. P to Q and Q to R
  • B. R to Q and Q to P
  • C. P to Q only
  • D. No net heat transfer between the blocks

4. In which states of matter can heat transfer by convection occur?

  • A. All three states
  • B. Liquids and gases
  • C. Gases only
  • D. Liquids only

5. A hot air balloon rises upwards in cold air. How does the volume and density of the balloon change when heated?

 Volume Density
A
 increases increases
B
 decreases increases
C
 increases decreases
D
 decreases decreases

6. The thermal energy transferred during conduction is written as ΔQ. Which of the following gives the correct units for the rate of thermal energy transfer and temperature gradient?

 Rate of thermal energy transfer Temperature gradient
A
 J K s-1
B
 W K s-1
C
 J K m-1
D
 W K m-1

 

7-9. These questions are about a copper rod heated at one end. The heat lost to the surroundings is negligible.

copper rod

The thermal conductivity k of copper is given as 400 W K-1 m-1. The temperature difference between the ends of the rod is 10 kelvin. The rod is 10 cm long and has a cross sectional area of 10-3 m.

 By Wdwd | CC BY-SA 3.0
7. The heat transferred per second is:
  • A. 0.4 J
  • B. 4 J
  • C. 40 J
  • D. 400 J

 

 

The rod is replaced by another with half the thermal conductivity and four times the length. The temperature difference and cross sectional area remain the same.

8. How does this affect the temperature gradient?

  • A. 2 times larger
  • B. 2 times smaller
  • C. 4 times larger
  • D. 4 times smaller

9. How does this affect the heat transfer per second?

  • A. 8 times smaller
  • B. 4 times smaller
  • C. 2 times smaller
  • D. remains the same

10. In cold countries, modern houses are built with thick, well insulated walls.

brick wall

  

10. Which of these sentences best explains why the rate of heat loss from the house is low?

  • A. The temperature gradient and the value of k are both low
  • B. The temperature gradient is high and the value of k is low
  • C. The temperature gradient is low and the value of k is high
  • D. The temperature gradient and the value of k are both high