3 Thermal Flashcards
Solid
Objects have fixed shape although this can be altered when forces act on them. They are usually dense (when compared to gases) and are very difficult to compress.
Liquids
Can flow or be poured from one container to another and when they are in the container they flow to the bottom. It is also difficult to compress a liquid.
Gases
Flow even more quickly than a liquid but they completely fill the container they are in instead of moving to the bottom. Gases are much easier to compress than either liquids or solids; their volume can be decreased significantly.
Gases and pressure
Adding more particles produces a larger force and makes the balloon inflate due to the increased pressure.
As the temperature rises, the gas particles move faster and collide with the balloon surface with more force and more often. These collisions on the internal surface of the balloon create gas pressure.
Brownian motion
The random motion of small, microscopic particles caused by collisions with even smaller, invisible particles. Named after Robert Brown’s observations of the movement of pollen grains in water.
Effects on pressure
Change in T at constant V: T^=P^, T!=P!
Change in V at constant T: V^=p!, V!=p^
Effect on pressure formula
PV = nPT
n=moles
R=constant
T= temp(K)
Kelvin
-273.15 °C
Specific heat capacity
The energy needed to change the temperature of a unit mass by a unit temperature
C=Change in Energy(E) ÷ Mass x change in temp
Internal energy
Is a measure of the average kinetic energy of the particles in a substance
Evaporation
A small amount of liquid will also change to a gas at temperatures lower than the boiling point.
Boiling is different as boiling happens throughout the liquid, not just at the surface, and at a specific temperature for the material.
Expansion and particle behaviour
Heating a material will increase the movement of the particles it is made from.
In a solid, they will stay in the same relative position but will move slightly further apart and take up slightly more volume.
In a liquid, the particles will also move faster and more freely when they are heated.
This is the same for a gas.
Conduction
Occurs in solids
Particle vibration(kinetic energy)
Delocalised electrons have a low specific heat capacity
Convection
When a part of a fluid is heated, it will expand – the particles move slightly further apart.
This means that the density of that region will decrease slightly, and that area is now less dense than the regions surrounding it.
A less dense material will float above a denser one and so the heated fluid will rise upwards, towards the surface if it is a liquid or to the top of the container if it is a gas.
Once the heated fluid reaches the surface, it will gradually cool and become denser again.
This will cause that part of the fluid to sink back downwards, especially if another part of the fluid is still being heated and rising upwards.
Radiation
This can occur in a vacuum
Travels as infrared waves
Dark/Dull colours absorb energy easily emitters and good emitters, but bad reflectors
Light/Shiny colours absorb energy badly and are bad emitters, good reflectors
Objects at a constant temp absorb and emit energy at the same rate.
