Course

A2 Physics: Thermal Physics (9702)

Name: A2 Physics: Thermal Physics (9702)
Price: 1799 BDT

9702 topics 14, 15 and 16. Temperature is not heat, and the difference is most of the marks: both come from the random motion of molecules, and this module makes that quantitative.

39 lessons3h 55mEnglish

What you'll learn

Say what temperature measures, and why two objects at the same temperature need not hold the same energy
Use c and L in a calorimetry calculation, including where the phase change hides the temperature rise
Apply pV = nRT, and derive pV = (1/3)Nm<c^2> rather than quoting it
State the first law with the sign convention the mark scheme expects
Explain a thermal process in terms of molecules, which is what the explain marks are for

Requirements

AS topic 5: work done as force times distance, and conservation of energy
O Level particle model: solids, liquids and gases as arrangements of moving particles
Comfortable with standard form and with units built from other units, such as J kg^-1 K^-1
Able to read a gradient and an area off a graph

Course content

39 lessons · 3h 55m

14.1-14.3 · Temperature

Temperature is not stored energy. What thermal equilibrium fixes, why the kelvin scale needs no substance at all, and how q = mcΔθ and the two latent heat plateaus account for every joule a heater supplies.

0/12

Temperature sets the direction, not the amount

A spoon in hot tea. Decide what has to become equal before the transfer stops.

Preview6m 2.

What a temperature reading actually measures

Raise the temperature of a gas and only one thing about the molecules changes.

Preview6m

A thermometer measures something else

No instrument can see kinetic energy, so every thermometer reads a stand-in property.

The scale that needs no substance

Convert a fever of 39 °C into kelvin, then find which equations refuse Celsius.

Why the scale has a bottom

Extend the pressure line of a cooling gas downwards and every gas meets zero at one place.

Same heater, same mass, different rise

Aluminium and lead under identical heaters. One of them gets hot far faster.

Determining c, and the error you must name

Pt = mcΔθ gives a number. Say why the experiment always makes that number too large.

The heater is on and the reading holds still

Two flat sections appear in a heating curve. Predict them before you press start.

Melting pays for spacing, not for speed

Ice floats because its lattice is open. Melting collapses that lattice, and that costs energy.

10.

Why boiling costs so much more than melting

A clay water pot on a hot afternoon, and the reason the water inside stays cool.

11.

One exam question, end to end

Nine marks, three parts, no options: find c, find the latent heat, then explain what poor insulation does.

12.

Temperature: quick revision

Reconnect equilibrium, heating and changes of state, then retrieve the distinctions exam questions test.

15.1-15.3 · Ideal gases

Counting molecules by weighing them, the equation of state pV = nRT, and the derivation that turns bouncing molecules into pressure. Ends where kinetic theory meets temperature: mean kinetic energy is three halves of kT.

0/12

Counting particles by weighing them

The mole is a count, not a mass and not a volume. Find the mass of one mole of oxygen.

Preview6m 2.

From moles to molecules, and back to one molecule

Kinetic theory needs the mass of a single molecule. A cylinder label gives you kilograms.

Preview6m

Halve the volume at fixed temperature

The molecules are not squeezed. Say what actually changes when the pressure doubles.

Heat it in a sealed can

Two separate effects raise the pressure together, and only kelvin makes the graph honest.

pV = nRT, and its twin pV = NkT

Three gas laws are one equation. Predict the volume of one mole before you compute it.

What the model agrees to ignore

Five assumptions, and the one that fails first when you compress a real gas hard.

Where pV = ⅓Nm⟨c²⟩ comes from

One molecule, one wall, one bounce. Then multiply by N and divide the directions by three.

Why the equation squares the speed first

Five speeds. Decide whether the mean of the squares equals the square of the mean.

Every gas, same temperature, same mean energy

Helium or oxygen at 300 K. Choose which one has the larger mean molecular kinetic energy.

10.

The cylinder that holds a liquid

An LPG cylinder breaks the ideal model on purpose. Name the assumption it breaks.

11.

One exam question, end to end

Nine marks, four parts, no options: amount, molecules, energy per molecule, then why the gas does not matter.

12.

Rebuild ideal gases in 7 minutes

Connect molecular motion to gas laws, rebuild the calculation route, then review weak ideas.

16.1-16.2 · Thermodynamics

Internal energy is what a body stores. Heating and doing work are the two processes that change it. The first law ΔU = q + w, the work w = -pΔV under a p-V graph, and why the path matters while the state does not.

0/12

A hot body does not contain heat

Name what is actually stored inside a warm gas, and what the word random rules out.

Preview6m 2.

The half of internal energy a thermometer misses

Melting ice absorbs energy at constant temperature. Decide whether internal energy changed.

Preview6m

Two processes, one result

Friction warms a track with no hot body anywhere. Say which process did it.

The first law and its signs

ΔU = q + w costs marks only through its signs. Fix the convention once, here.

Work done by an expanding gas

A piston moves out at constant pressure. Derive w = -pΔV in three lines.

Two paths, same states, different work

Same start, same end, two routes. Predict whether the work done is the same.

Compress it and keep the temperature

A cylinder in a large water bath. Work is done on the gas, so where does it go?

No heating, so the temperature must move

Set q to zero and the first law has only two terms left. Predict the temperature.

A sealed pot does no work at all

A pressure cooker on a Dhaka stove, and why the rice cooks faster inside it.

10.

Round a closed loop, ΔU is zero

An engine returns to its starting state every cycle. Say what that forces q + w to be.

11.

One exam question, end to end

Eight marks, three parts, no options: the work done, the change in internal energy, then the temperature.

12.

Thermodynamics: quick revision

Reconnect heat, work and internal energy, then rehearse the sign choices behind every gas process.

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