# Physics- P1 ~ Matter

OCR Gateway Physics P1 Matter: Topic Summary

• Physics- P1 ~ Matter
• Density
• Density = Mass (kg) / Volume (m^3)
• Different densities have different states; solids, liquid & gas
• Different densities also have different masses of atoms
• Different densities all have a different  arrangement
• Air & Water
• There is less air pressure up a mountain, it increases as you go down
• Difference in liquid pressure between A and B (Pa) = height of column (m) x density of liquid (kg/m^3) x g (N/kg)
• Water pressure is less at the surface, increases as you go down
• Pressure depends on  depth and density of liquid
• Changes of State
• Mass is conserved when substances change state
• Heating increases energy stored which changes state (physical change, not chemical reaction, can be reversed
• Thermal energy for a change in state (J) = mass (kg) x specific latent heat (J/kg)
• Change in thermal energy (J) = mass (kg) x specific heat capacity (J/kg celsius) x change in temperature (celsius)
• Atoms
• Everything is made up of atoms. Atoms are about 10^-10 in diameter
• Pressure
• Gas pressure is from molecules colliding so temperature & pressure goes up
• Pressure & volume, changing volume changes pressure, or vice versa
• Pressure (Pa) x Volume (m^3) = constant
• Pa = pascals = 1 N / m^2
• Atmospheric Pressure- If we assume our atmosphere has uniform density : Pressure is bigger near surface of Earth due to weight of air above
• Atmospheric pressure = 100 kPa