5.1. Thermal Physics

Question 1

What is thermal equilibrium?

Answer 1

Two objects are in thermal equilibrium when there is no net flow of thermal energy between them. Any objects in thermal equilibrium must be at the same temperature.

Question 2

What is the relationship between absolute temperatures and the properties of the material?

Answer 2

Totally independent of one another.

Question 3

What is Brownian motion?

Answer 3

• Brownian motion is the continuous random motion of small particles suspended in
  a fluid, visible under a microscope.
• This proves that matter is made up of small molecules with mass and energy. Molecules in the fluid move randomly and collide with the small particles, causing their continuous random motion.

Question 4

How can you observe Brownian motion of smoke in air?

Answer 4

• Smoke particles are large enough to see under a microscope.
• The paths of these smoke particles appear random.
• This is caused by air molecules continuously colliding with the smoke particles.
• The mean kinetic energy of the smoke particles is the same as the mean kinetic energy of the air molecules (however, due to their different masses, air molecules move much faster than smoke particles).

Question 5

What apparatus is used to investigate the specific heat capacity of a solid or liquid?

Answer 5

• Solid block or beaker of liquid
• Heater and thermometer inserted into the material (suspended in the liquid or in a hole in the solid block)
• Insulation on the outside of the block or beaker (including insulation or a lid on top)
• heater connected to circuit with a power supply and variable resistor, voltmeter and ammeter
• a stopwatch to measure the time

Question 6

What techniques and procedures are used to determine the specific latent heat of fusion of a substance?

Answer 6

• Set up ice in a funnel over a beaker. Put a thermometer and a heater in the ice and connect it to a circuit with a power supply, variable resistor, ammeter and voltmeter.
• Increase the current to the heater until the thermometer is at the melting point.
• Measure the current and voltage, and use a stopwatch to get time.
• measure the mass of the water that had melted into the beaker below.
• Repeat to get a mean, use insulation etc. for better accuracy and precision.
• Use P=IV, E=Pt and E=mL to find L

Question 7

What techniques and procedures are used to determine the specific latent heat of vaporisation of a substance?

Answer 7

• Set up a flask to hold the liquid with a heater in it. then connect this to a condenser leading to a collecting flask, where gas can condense and be collected.
• Connect to a circuit with ammeter, voltmeter, power supply, variable resistor.
• measure time, current, voltage and the mass of liquid collected from the condenser.
• Repeat to get a mean, use insulation etc. to
• Use P=IV, E=Pt and E=mL to find L