Pressure, Volume, Temperature
Gases
are molecules moving at such high speeds that they expand to
completely fill their container. The total amount of space in the
container is the volume, the speed of the molecules is
measured as temperature and the total amount of force felt by
the walls of the container (since the molecules keep colliding with
it) is the pressure.
One of the weird things about pressure, volume and temperature is that they can be measured with different units. You're probably already familiar with the units of ºC, Kelvin (K) and maybe even Fahrenheit (ºF).
For pressure, we have different units as well:
“atmospheres”: 1 atm = approximately atmospheric pressure
“kilopascals”: 101.3 kPa = 1 atm
“millimetres of mercury”: 760 mmHg = 1 atm
“torr”: 760 torr = 1 atm
Note that “torr” and “mmHg” are the same unit, but are just given different names.
You can be expected to interconvert all of these different units. When I'm doing chemistry problems, I convert ALL pressures to “atm” by default, just because it's easier for me to keep track of.
For volume, we have:
“millilitres”: 1 mL = 1 cm3
“litres” 1 L = 1000 mL = 1 dm3
Note that “mL” and “cm3” are the same unit, but are just given different names.
Note that “L” and “dm3” are the same unit, but are just given different names.
For MOST problems, I convert all volumes to litres or millilitres. The only exception is when there are problems about crystalline solids ... but you'll know those when you see them.
Be familiar enough with these units that they don't scare you to see them used.
One of the weird things about pressure, volume and temperature is that they can be measured with different units. You're probably already familiar with the units of ºC, Kelvin (K) and maybe even Fahrenheit (ºF).
For pressure, we have different units as well:
“atmospheres”: 1 atm = approximately atmospheric pressure
“kilopascals”: 101.3 kPa = 1 atm
“millimetres of mercury”: 760 mmHg = 1 atm
“torr”: 760 torr = 1 atm
Note that “torr” and “mmHg” are the same unit, but are just given different names.
You can be expected to interconvert all of these different units. When I'm doing chemistry problems, I convert ALL pressures to “atm” by default, just because it's easier for me to keep track of.
For volume, we have:
“millilitres”: 1 mL = 1 cm3
“litres” 1 L = 1000 mL = 1 dm3
Note that “mL” and “cm3” are the same unit, but are just given different names.
Note that “L” and “dm3” are the same unit, but are just given different names.
For MOST problems, I convert all volumes to litres or millilitres. The only exception is when there are problems about crystalline solids ... but you'll know those when you see them.
Be familiar enough with these units that they don't scare you to see them used.
