A2 Unit G484: The Newtonian World

Module 1: Newton’s laws and momentum• 4.1.1 Newton’s laws of motion

• 4.1.2 Collisions

Module 2: Circular motion and oscillations• 4.2.1 Circular motion

• 4.2.2 Gravitational Fields

• 4.2.3 Simple harmonic oscillations

Module 3: Thermal Physics• 4.3.1 Solid, liquid and gas

• 4.3.2 Temperature

• 4.3.3 Thermal properties of materials

Module 3: Thermal Physics

• 4.3.1 Solid, liquid and gas

• 4.3.2 Temperature

• 4.3.3 Thermal properties of materials

What is the difference between heat and temperature?

Is there a

maximum temperature?

4.3.2 TemperatureYou should be able to:

(a) Explain that thermal energy is transferred from a region of higher temperature to a region of lower temperature;

(b) Explain that regions of equal temperature are in thermal equilibrium;

(c) Describe how there is an absolute scale of temperature that does not depend on the property of any particular substance (ie the thermodynamic scale and the concept of absolute zero);

(d) Convert temperatures measured in kelvin to degrees Celsius (or vice versa):

T (K)= θ (°C) + 273.15;

(e) State that absolute zero is the temperature at which a substance has minimum internal energy.

What unit is this?

°C

°CWhat unit is this?

• The Celsius scale is an absolute scale.• It is the absolute thermodynamic scale

minus 273.15 exactly.

Absolute scale/K Celsius Scale/oC

Absolute zero 0 -273.15

Triple point of water 273.16 0.01

Ice point 273.15 0.00

Steam point 373.15 100.00

Why did Einstein win a Nobel prize?

Because of his work on the photoelectric effect and on

kinetic theory.

The First Law of Thermodynamics

Change in Internal Energy = Heat Transfer + Work Done

ΔU = ΔQ + ΔW

i.e. if you put energy into a system, its internal energy will increase

An Obvious Law of Thermodynamics

Thermal energy is transferred from a region of higher temperature to a region of lower temperature.

The Zeroth Law of Thermodynamics

If A is in equilibrium with B, and B is in equilibrium with C, then A and C must be in equilibrium.

A CB

• Read pages 296-300 in APFY• Complete questions 1,2,3 and 4 on page

305

The rms speed of the molecules in a gas is 600ms-1 and the mass of the molecules is 4.6 x 10-26 kg. What is the temperature of the gas in degrees Celsius? 127oC

4.3.3 Thermal properties of materials

You should be able to:

(a) Define and apply the concept of specific heat capacity.

(b) Select and apply the equation E = mcΔθ

(c) Describe an electrical experiment to determine the specific heat capacity of a solid or a liquid.

(d) Describe what is meant by the terms latent heat of fusion and latent heat of vaporisation.

Specific Heat Capacity

The specific heat capacity is the energy needed to raise the temperature of 1 kg by 1 K

ΔU = m c Δθ change in = mass x specific heat x temperature

internal energy capacity change

Calculating the specific heat capacity of a metal

Calculating the specific heat capacity of a metal

mm= mass of metal [kg] =

cm = s.h.c of the metal [J kg-1 K-1] = ?

θm = initial temperature of the metal [K or oC] =  

Calculating the specific heat capacity of a metal

mw= mass of water [kg] =

cw = s.h.c of the water [J kg-1 K-1] = 4180 J kg-1 K-1

θw = initial temperature of the water [K or oC] =

Calculating the specific heat capacity of a metal

Once in thermal equilibrium…

 θf = final temperature of the water and metal =

Calculating the specific heat capacity of a metal

Thermal energy lost by metal = mmcmΔθ Thermal energy gained by water = mwcwΔθ

θw final = θm final

mmcmΔθ = mwcwΔθ

cm = mwcw(θw final – θw initial) mm(θm initial – θm final)