Year 1 Sem 2/LC Temperature and Matter/Lecture 01
Course Welcome
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Study guide and full revision notes (from Prof. Mike Gunn) on Canvas.
- The course has changed a bit recently, so the full revision notes have additional theory/content which isn’t examinable.
- Series of non-assessed problems also on Canvas.
Course Aims
We want to be able to explain the properties of matter (in the macroscopic world) of various kinds, based on their microscopic behaviour. We also want to be able to understand more about the microscopic behaviour of matter from macroscopic observables.
Recommended Reading
- Young and Freedman, Ch14 and Ch17-19.
- Properties of Matter, Flowers and Mendoza.
- Introduction to Thermal Physics, Adkins.
Intro to Matter
States of Matter
We want to move away from a simple "cold stuff is a solid, warmer stuff is a liquid and hotter stuff is a gas" by also considering how different materials change state as a function of both pressure and temperature:
At “Standard Pressure and Temperature” (at $20 \mathrm{^\circ\!C}$ and $1$ATM), we see that increasing pressure of C02 takes it to a liquid state. However, at lower temperatures, decreasing the pressure can cause it to sublimate straight from a solid to a gas, without a liquid intermediary.
Taking water as an example, pushing the pressure/temperature causes another high-energy state altogether called a “supercritical fluid”. The gradient for the initial vertical portion of the solid/liquid boundary around the freezing point is slightly negative, so applying pressure to ice on this boundary causes it to become liquid. This is uncommon for many materials.
This is because water is weird, where the solid form is less dense than the liquid form. This is how ice skating works, where applying pressure (from a skate) causes a thin upper layer of ice to melt. This thin water layer is what the ice skate can travel on.
Every material also has a “triple point” where the material can act simultaneously in all three standard states of matter.