Solids, Liquids and Gases FULL NOTES

These are my class notes for GCSE PHYSICS topic SOLIDS, LIQUIDS AND GASES.

If you learn these you're bound to get an A*

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- Paige

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  • Created by: Paige
  • Created on: 27-01-14 18:44
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Solids, Liquids and Gases
SO what's density? Well, all solids, liquids and gases have different properties and characteristics.
One such characteristic is density. Solids are often very dense, liquids are less dense than solids, and
gases have very low densities. Density is how much mass something has for a certain volume ­ in
other words, how `squashed up' something is.
To calculate density, use this equation:
Density = Mass/Volume
P = m/v
Example: A piece of iron has a mass of 390kg and a volume of 0.05m3. What is its density?
P = m/v
P = 390kg/0.05m3
= 7800kg/m3 Remember the unit! Density can be kg/m3, g/cm3...etc
Calculating Volumes for the Density
For a cuboid like this, simply multiply its length, width and height. I'm assuming
you know this, but if not, work up your maths man...
As for irregular solids, measure out a certain
amount of water with a measuring
cylinder. This is the control (something to
compare results to). Do the same with
another measuring cylinder, and drop the solid in. Note the rise in
the level of water. The difference between the two measurements
is the volume of the solid, in this case, 10ml.
Pressure in Solids
Lets start like this: You can easily push a pin into a piece of wood quite easily, but it is pretty much
impossible to make a hole in the wood with your finger. You can try with little success (and end up with
splinters all over your fingers). Why is that? The small point of the drawing pin concentrates all your
pushing force into a tiny area, so the pin goes into the wood easily.
To get to the point, pressure is defined as the force per unit area. Force is measured in newtons (N)
and area is measured in square metres (m2). The unit for pressure is N/m2 or Pa (for Pascals).
Unfortunately, there is an equation that comes with pressure and this is ONLY FOR SOLIDS:

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Pressure (in Pascals) = Force (in newtons)/Area (in square metres)
p = f/a
Example: A woman weighs 600N and the total area of her shoes in contact with the ground is
0.0015m2. Find the pressure she is exerting to the ground.
p = f/a
p = 600N/0.0015m2
= 400000Pa (or 400kPa)
Pressure in Liquids and Gases
Pressure in liquids act equally in all directions as long as the liquid is not moving. This is the same for
gases.…read more

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And in words...
Boyle's Law: At a constant temperature and with a fixed mass of gas, pressure is inversely
proportional to volume.
Question: How does a gas exert a pressure on the walls of its container?
Billions of tiny air particles move about in continual random motion. Particle collisions with the walls of
the container exerts a force, which gets distributed over the area of the wall of the container, hence,
exerting a pressure.…read more

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We must first convert the temperature in Kelvin, so:
T1 = 20 + 273 = 293K (This is the temperature OUTSIDE the tin)
T2 = 50 + 273 = 323K (This is the temperature INSIDE the tin)
p1/T1 = p2/T2
100kPa/293K = p2/323K
p2 = 110kPa
Now to summarise the Pressure Law:
Pressure Law: With a fixed mass of gas at a constant volume, pressure is proportional to temperature
(in Kelvins).…read more


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