1. Thermodynamics

2. Thermodynamics Temperature Particles Pressure, volume and temperature
Energy and Power
Heat transfer
Measuring Temperature
Specific heat capacity
Latent heat

3. Energy

4. Energy (Joule) Energy can be transferred or transformed kinetic
potential (chemical, electrical, gravitational, elastic)
radiant (sound, light and other electromagnetic waves)
internal (heat/thermal energy)

5. Temperature

6. Temperature
The temperature of an object is given by the average kinetic energy of its particles.

7. 2. Measuring temperature
Which thermometers use thermal expansion as their thermodynamic property?
a) liquid in glass
b) thermistor
c) constant volume gas thermometer
d) thermocouple

8. a) liquid in glass

9. Temperature Scales use a thermodynamic property
scales calibrated at 2 fixed points (often melting ice and boiling water

10. Internal Energy

11. Internal Energy
The internal energy of an object is the total kinetic and potential energies of the particles.
U = EK +EP

12. 5. Internal Energy
During a change of state from solid to liquid at the melting point:
a) the temperature of the substance stays the same
b) the internal energy of the substance stays the same
c) the kinetic energy of the particles stays the same

13. Internal Energy
Internal Energy = potential energy of particles + kinetic energy of particles U = PE + KE Heat  increases internal energy

14. a) the temperature of the substance stays the same and c) the average kinetic energy of the particles stays the same

15. Which liquid has more internal energy?
cup of hot tea 80oC
water in swimming pool 25oC

16. Thermal equilibrium

17. Temperature
average kinetic energy of a particle different temperatures  heat transferred until thermal equilibrium
States of matter

18. 1. Thermal Equilibrium When two objects are in thermal equilibrium:
their particles are moving at the same speed
they each contain the same amount of internal energy
the average kinetic energy of the particles in each object is the same

19. c) the average kinetic energy of the particles in each object is the same

20. Heat transfer
Which ice cube will melt first?

21. Gases

22. The Ideal Gas
all collisions between atoms or molecules are perfectly elastic no intermolecular attractive forces
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23. Charles’ Law
Charles’ Law: the volume of a gas is proportional to the Kelvin temperature at constant pressure V = kT V1 = T1 V2 T2

24. Absolute zero
Absolute zero is the temperature at which the particles of a substance have no kinetic energy. This occurs at -273oC.

25. Kelvin temperature scale
The Kelvin scale of temperature is defined by absolute zero and is designed so that 1 Kelvin = 1 oC. This gives absolute zero (0K) as oC.

26. Convert temperatures to Kelvin. 40C = 313K 75C = 348K
Example: Calculate the volume at 75ºC of of a gas sample that at 40ºC occupies a volume of 2.32 dm3
Convert temperatures to Kelvin. 40C = 313K
75C = 348K
2.32 dm3 = 313 K
V K
(313K)( V2) = (2.32 dm3) (348K)
V2 = 2.58dm3

27. Heat Transfer

28. How is heat transferred?
Conduction
Convection
Radiation

29. specific heat capacity
How much energy is needed to increase temperature?

30. Heat capacity
Describe what happens to the temperature of liquid coffee at 90°C when it is poured into a cup at room temperature.
Which direction does heat flow?
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31. Heat capacity
The heat capacity of an object is the energy required to raise its temperature by 1°C
Image:

32. Heating water
It takes 4180J of heat energy to increase the temperature of 1kg of water by 1°C. a) how much heat is needed for 0.5kg by 1°C? b) how much heat is needed for 1kg from 20 to 50C? c) how much heat for 5kg from 20 to 100C?

33. specific heat capacity
Heat energy = mass of × specific heat × temperature substance capacity change E = m × c × ∆T (J) (kg) (J/kg/°C) (°C) The specific heat capacity is the amount of heat needed to raise the temperature of a mass of one kilogram of a substance by 1 degree Celcius.

34. Coffee example

35. 6. Specific Heat Capacity
Specific heat capacity of water is 4180J/kg/K
This means 4180J of energy is needed to
a) increase the temperature of 10g of water from 20 to 30C
b) increase the temperature of 1 litre of water from 20 to 21C
c) increase the temperature of 0.1kg of water from 40 to 50C

36. b) increase the temperature of 1 litre of water from 20 to 21C and c) increase the temperature of 0.1kg of water from 40 to 50C

37. Specific Heat Capacity
E = mcΔT
shc found from 'the electrical method' or 'the method of mixtures'.

38. Latent heat

39. Latent Heat
Latent heat of fusion: energy needed to melt a solid without a temperature rise
Latent heat of vaporization: energy needed to boil a liquid without a temperature rise.
Energy = mass × spedific latent heat
E = mL

40. Ideal gases

41. 3. Temperature and Pressure
The temperature of an ideal gas (in Kelvin) is proportional to its pressure so
a) at absolute zero the pressure is zero
b) at absolute zero the particles have no kinetic energy
c) below absolute zero the pressure is negative

42. at absolute zero the pressure is zero and b) at absolute zero the particles have no kinetic energy

43. Pressure
Gas pressure due to collisions of gas particles with container walls.
Higher temperature > more collisions, more KE
Unit of pressure: Pascal 1 Pa = 1 N/m2

44. 4. Pressure, Volume and Temperature
When the pressure of an ideal gas is doubled
a) the volume is half if the temperature is kept constant
b) the volume is double if the temperature is kept constant
c) the temperature is double if the volume is kept constant

45. the volume is half if the temperature is kept constant and c) the temperature is double if the volume is kept constant

46. Pressure, Volume and Temperature
P1V1 = P2V2 for a fixed mass of gas
T T2