IGCSE PHYSICS – TOPIC 5
SOLIDS, LIQUIDS AND GASES
a) DENSITY AND PRESSURE
DENSITY:
• DENSITY – the mass per unit volume of a material
o Objects made from low density materials, typically have a low
mass, whilst similar sized objects made from high density materials
have a high mass:
Density (g/cm3 or kg/m3) = Mass/ Volume
ρ = m/V
PRACTICAL TO INVESTIGATE: the density of regular
or irregular shaped objects
Method (REGULAR):
• The width and length or an object can be
measure using digital calipers
• Several measurements to be taken and
average calculated
• Calculate the volume
• Measure the mass using a balance
• Use equation ρ = m/V to find the density
PRACTICAL TO INVESTIGATE: the density of regular
or irregular shaped objects
Method (IRREGULAR):
• Fill a Eureka can with water
• Place an empty measuring cylinder below it’s
spout
• Now carefully lower the object into a Eureka
can (using a piece of string)
• Measure the volume of water displace water
(the volume of the object) and use equation
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, PRESSURE:
• PRESSURE – the concentration of a force
o If a force is spread over a large area there will be a smaller
pressure, but if there is a force over a small area there will be a
bigger pressure
Pressure (N/cm2 or N/m2 or Pa) = Force/ Area
P = F/A
• When an object is immersed in a liquid, the liquid exert a pressure,
squeezing the object
• The pressure is exerted EVENLY ACROSS THE WHOLE SURFACE AREA
of the liquid, IN ALL DIRECTIONS:
Pressure (N/cm2 or N/m2 or Pa) = Height x Density x Gravitational Field
Strength
P=hxρxg
b) CHANGE OF STATE
• The molecules within a substance have two 2 types of energy –
KINETIC ENERGY (vibration) and POTENTIAL ENERGY (bonds between
molecules) – these make up THERMAL ENERGY of that substance –
when heated kinetic energy INCREASES
• The TEMPERATURE OF THE MATERIAL is related to the KINETIC
ENERGY of the molecules
• When the substance reaches a specific temperature, the kinetic
energy will stop increasing and the heat will go to POTENTIAL ENERGY
and the bonds will BE BROKEN and the material CHANGES STATE
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SOLIDS, LIQUIDS AND GASES
a) DENSITY AND PRESSURE
DENSITY:
• DENSITY – the mass per unit volume of a material
o Objects made from low density materials, typically have a low
mass, whilst similar sized objects made from high density materials
have a high mass:
Density (g/cm3 or kg/m3) = Mass/ Volume
ρ = m/V
PRACTICAL TO INVESTIGATE: the density of regular
or irregular shaped objects
Method (REGULAR):
• The width and length or an object can be
measure using digital calipers
• Several measurements to be taken and
average calculated
• Calculate the volume
• Measure the mass using a balance
• Use equation ρ = m/V to find the density
PRACTICAL TO INVESTIGATE: the density of regular
or irregular shaped objects
Method (IRREGULAR):
• Fill a Eureka can with water
• Place an empty measuring cylinder below it’s
spout
• Now carefully lower the object into a Eureka
can (using a piece of string)
• Measure the volume of water displace water
(the volume of the object) and use equation
30
, PRESSURE:
• PRESSURE – the concentration of a force
o If a force is spread over a large area there will be a smaller
pressure, but if there is a force over a small area there will be a
bigger pressure
Pressure (N/cm2 or N/m2 or Pa) = Force/ Area
P = F/A
• When an object is immersed in a liquid, the liquid exert a pressure,
squeezing the object
• The pressure is exerted EVENLY ACROSS THE WHOLE SURFACE AREA
of the liquid, IN ALL DIRECTIONS:
Pressure (N/cm2 or N/m2 or Pa) = Height x Density x Gravitational Field
Strength
P=hxρxg
b) CHANGE OF STATE
• The molecules within a substance have two 2 types of energy –
KINETIC ENERGY (vibration) and POTENTIAL ENERGY (bonds between
molecules) – these make up THERMAL ENERGY of that substance –
when heated kinetic energy INCREASES
• The TEMPERATURE OF THE MATERIAL is related to the KINETIC
ENERGY of the molecules
• When the substance reaches a specific temperature, the kinetic
energy will stop increasing and the heat will go to POTENTIAL ENERGY
and the bonds will BE BROKEN and the material CHANGES STATE
31
