Solids, liquids, and gases
Density
m
Density ¿ ⍴=
v
Density is mass per unit volume
Investigating density of solids
- For a regular solid, find volume (e.g. by multiplying length, width, and height)
- For an irregular solid, measure volume of liquid displaced (using eureka can)
o Make sure measuring cylinder is on level surface and avoid parallax error
- Use weighing scales to measure mass of solid, divide mass by volume
Pressure
force (N) F
Pressure ( Pa ) = 2 p=
area(m ) A
Pressure is force per unit area
Pressure in liquids and gases act equally in all directions, as long as the liquid or gas is not moving
Pressure difference in two points in a liquid/gas:
Pressure difference ( Pa )=height ( m ) × gravitational field strength ¿
p=h× g× ⍴
(Consider liquid as a column between 2 points to work out pressure difference)
Solids, liquids, and gases
State Solid Liquid Gases
Density High- closely Medium- Low- far apart
packed closely packed
Arrangemen Regular lattice Randomly Randomly arranged
t of particles arrangement arranged
Movement Vibrate around Move freely Move quickly in all directions
of particles each other around each
(move randomly and in straight lines
other
between collisions)
Energy of Low Greater Highest
particles
Shape and Fixed shape and No fixed No fixed shape or volume, can be
volume volume shape, fixed compressed because there are large gaps
volume between particles and it is easier to push
particles close together
2D diagram
Density
m
Density ¿ ⍴=
v
Density is mass per unit volume
Investigating density of solids
- For a regular solid, find volume (e.g. by multiplying length, width, and height)
- For an irregular solid, measure volume of liquid displaced (using eureka can)
o Make sure measuring cylinder is on level surface and avoid parallax error
- Use weighing scales to measure mass of solid, divide mass by volume
Pressure
force (N) F
Pressure ( Pa ) = 2 p=
area(m ) A
Pressure is force per unit area
Pressure in liquids and gases act equally in all directions, as long as the liquid or gas is not moving
Pressure difference in two points in a liquid/gas:
Pressure difference ( Pa )=height ( m ) × gravitational field strength ¿
p=h× g× ⍴
(Consider liquid as a column between 2 points to work out pressure difference)
Solids, liquids, and gases
State Solid Liquid Gases
Density High- closely Medium- Low- far apart
packed closely packed
Arrangemen Regular lattice Randomly Randomly arranged
t of particles arrangement arranged
Movement Vibrate around Move freely Move quickly in all directions
of particles each other around each
(move randomly and in straight lines
other
between collisions)
Energy of Low Greater Highest
particles
Shape and Fixed shape and No fixed No fixed shape or volume, can be
volume volume shape, fixed compressed because there are large gaps
volume between particles and it is easier to push
particles close together
2D diagram
