This clear and concise summary of the key topics from Thermal Physics covered during A-level will give you all the information necessary to ace your exam. It covers all of the the essential definitions and background physics necessary, to make it as easy a read as possible. Every vital equation nee...
1 Introduction
Thermal physics is a combination of three areas of study in physics which include
Statistical Physics(which aims to describe physical phenomena by using statis-
tical methods and probability theory),Thermodynamics(the study of heat, work
and temperature and their relation to energy and entropy) and Kinetic theory
of gases which is a classical model for the thermodynamic behaviour of gasses;
modelling them as submicroscopic particles in constant, random motion. Thank-
fully in this topic we will only worry about the results from these three branches
of physics and mainly ignore the underlying math which can become quite com-
plex.
2 Thermal energy transfer
The internal energy of a substance is equal to the sum of the kinetic and potential energies
of all it’s particles. Since the particles move randomly this means that the poten-
tial and kinetic energies are randomly distributed throughout the substance.
We can increase the internal energy of a system by doing two things;
• We can do work on the system i.e by moving particles or changing the
shape by applying a force.
• Increasing the temperature of the system will increase the kinetic energy
of the constituent particles thus increase the internal energy.
, When the state of a substance changes,its internal energy also changes. This is
due to the fact that the potential energy of the substance changes while the ki-
netic energy remains constant. A good example is that of frozen water; the water
reaches its freezing point of 0∘ c and its kinetic energy remains constant while the
potential energy decrease as Hydrogen bonds within the object form.
Given below is the graph of temperature 𝑇 against internal energy 𝑈 of a sub-
stance:
𝑇
Gas
Liquid
Boiling Point
Solid
Melting Point
𝑈
The amount of heat gained or lost by a substance 𝑄 is given by the equation,
𝑄 = 𝑚𝑐Δ𝜃 (0.1)
where 𝑚 is the mass of substance, 𝑐 is the specific heat capacity of the sub-
stance(which is substance specific) and Δ𝜃 is the change in temperature expe-
rienced by the substance given in Kelvin(K).
The Specific heat capacity of a substance is defined to be - The amount of
energy required to increase the temperature of 1kg of a substance by 1∘ c/1K,
without changing its state.
By using some dimensional analysis we can easily find the units of 𝑐, to start
we know that the units of heat is J thus we have,
[𝑄] = J = [𝑚𝑐Δ𝜃] = Kg K ⋅ 𝑋
2
The benefits of buying summaries with Stuvia:
Guaranteed quality through customer reviews
Stuvia customers have reviewed more than 700,000 summaries. This how you know that you are buying the best documents.
Quick and easy check-out
You can quickly pay through credit card for the summaries. There is no membership needed.
Focus on what matters
Your fellow students write the study notes themselves, which is why the documents are always reliable and up-to-date. This ensures you quickly get to the core!
Frequently asked questions
What do I get when I buy this document?
You get a PDF, available immediately after your purchase. The purchased document is accessible anytime, anywhere and indefinitely through your profile.
Satisfaction guarantee: how does it work?
Our satisfaction guarantee ensures that you always find a study document that suits you well. You fill out a form, and our customer service team takes care of the rest.
Who am I buying these notes from?
Stuvia is a marketplace, so you are not buying this document from us, but from seller DylanStanden. Stuvia facilitates payment to the seller.
Will I be stuck with a subscription?
No, you only buy these notes for £6.49. You're not tied to anything after your purchase.
