3.1 - Thermal concepts - questions

1 - How is temperature explained in the particle model ?

2 -

3 - What are the three states of matter ?

4 - How do you convert from Celsius to Kelvin degrees ? What is 20K in C ?

3.2 - Thermal properties - questions

5 - What is thermal capacity ?

6 - What is the formula for thermal capacity ?

7 - What is specific heat capacity ?

8 - What is the formula for specific heat capacity ?

9 - What is the relationship between thermal capacity and specific heat capacity ?

10 - What is specific latent heat ?

11 - What is the formula for specific latent heat ?

12 - How do the temperature change when matter changes state ? Ice melts for example.

13 - There are two different specific heats. What are they called ?

14 - How is power defined ?

The figure below shows how 1kg of water is heated without energy loss to the room.
For water c = 4200 J/kg/C and L=2.27 x 10⁶ J/kg .

15 - Calculate how much power is needed to heat the water in this way !

16 - Calculate how much water is boiled away if the power is 700 W !

17 - The curve above shows how the temperature changes without energy loss. In reality there will be an energy loss. Draw a more realistic curve with energy loss.

18 - Use the information in the figure below and the specific heat capacity of water (4180) to calculate the specific heat capacity of the metal.

19 - Use the information in the figure below to calculate the latent heat of vaporization.
The temperature of the water goes up 20 ^oC.
The steam goes down in temperature with 30 ^oC.

3.3 - Ideal gas - questions

20 - How can temperature be explained in the ideal gas model ?

21 - How can pressure be explained in the ideal gas model ?

22 - How do the pressure change if the volume of a gas is decreased ?

23 - How do the pressure change if the temperature of a gas is increased ?

3.1 - Thermal concepts

a) Work = Force x distance   → work is being made on the block.
b) Work is done on the block  →  energy is being transferred to the block.
c) E_k = mv²/2  →  Since m and v are constant, E_k is not changing.
d) E_p = mgh  → Since m and h are constant, E_p is not changing.
e) The energy is used to overcome the friction and in this process the block will be heated up so the energy is transformed into increased temperature which is equal to increased kinetic energy of the particles inside the block (but not an increase of the kinetic energy of the block as a whole). We say that the internal energy of the block has increased.

3.2 - Thermal properties

Look at the data booklet:

Look at the data booklet:

The figure below shows how 1kg of water is heated without energy loss to the room.
For water c = 4200 J/kg/C and L=2.27 x 10⁶ J/kg .


Calculate how much power is needed to heat the water in this way !

P = Q / t

Q = m c ΔT

Combining these two formulas give
P = m c ΔT / t
P = 1 x 4200 x 80 / 240 = 700 W

Calculate how much water is boiled away !

P = Q / t

Q = m L

Combining these two formulas give
P = m L / t
m = P t / L = 700 x 480 / 2.27 x 10⁶ = 0.15 kg


This is the way that the same problem is solved in the book:

The curve above shows how the temperature changes without energy loss. In reality there will be an energy loss. A more realistic curve with energy loss looks like this:

3.3 - Ideal gas

Look at the data booklet: