SCI_MODULE_01a_i_MATERIALS_STATES_OF_MATTER

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MATERIALS
Module 01a(i)
States of matter
States of matter
State the distinguishing properties of
solids, liquids and gases.
Matter
• The ‘stuff’ that everything is made from
• Made up of particles
• http://www.harcourtschool.com/activity/state
s_of_matter/
There are three states of matter
Relate the properties of solids, liquids and gases to the
forces and distances between molecules and to the
motion of the molecules
• http://lgfl.skoool.co.uk/content/keystage3/ch
emistry/pc/learningsteps/SLGLC/launch.html
Bonds holding the
particles together
Very weak bonds
vary in strength
Changes from one state to another
• Need energy because:Particles move faster
• This energy is supplied in the form of
Heat
"Latent heat" is the term used to describe
energy which causes a change of state
without change of temperature.
Sublimation
Melting
Solidification or freezing
Evaporating
Condensing
Molecular model
Describe qualitatively the molecular
structure of solids, liquids and gases.
• This means you should be able to describe
how the particles are arranged in solids,
liquids and gases
• Supplying or removing heat energy changes
the movement of the particles
• This changes the arrangement of the particles
and therefore the state
You can change the state of a substance by
heating or cooling it.
• When the change is from a liquid to a solid it
is called freezing.
• When the change is from a gas to a liquid it is
called condensing.
• When the change is from a solid to a liquid it
is called melting.
• When the change is from a liquid to a gas it is
called boiling or forced evaporation.
Relate the properties of solids, liquids and gases to the forces
and distances between molecules and to the motion of the
molecules.
• The particles in solids are held most strongly
and move the least
• The particles in gases are held together least
strongly and move fastest
Interpret the temperature of a gas in
terms of the motion of its molecules
• The higher the
temperature the
faster the
molecules move
•
http://www.epa.gov/apti/bces/m
odule1/kinetics/animation/kani1/
kani104.htm
Changes of state
Describe qualitatively the pressure of a gas
in terms of the motion of its molecules.
• It is the force of
collision and the
number of collisions
with the walls of a
container that cause
gas pressure
• This pressure is
measured in terms of
the force per unit area.
Describe qualitatively the effect of a change of temperature on
the pressure of a gas at constant volume
• As temperature increases
• The pressure of gas increases
• Because the molecules move faster and hit the
sides of the container more frequently
Relate the change in volume of a gas to change in pressure applied to
the gas at constant temperature and use the equation pV = constant
at constant temperature
• Pressure is inversely
proportional to the
volume
• As an equation this is
P1V1=P2V2
• Where P=pressure &
v=volume
• 1 & 2 refer to original
values and altered values
• Or PV = constant.
•
http://www.grc.nasa.gov/WWW/k12/airplane/aboyle.html
Evaporation
Describe evaporation in terms of the escape of more
energetic molecules from the surface of a liquid.
• As molecules are heated they gain energy
• The liquid molecules gain enough energy to
escape from the surface
• This is evaporation
• Look at this animation
• http://www.absorblearning.com/media/attac
hment.action?quick=t1&att=2080
Demonstrate understanding of how temperature,
surface area and air flow over a surface influence
evaporation.
• http://www.ehow.com/info_10041602_experime
nts-evaporation-surface-area.html
• Higher temp means more energetic molecules –
more can escape – more evaporation
• More surface area more area over which
molecules can escape
• Air flows removes evaporated
molecules
• This means there is more space for molecules to
move into – more evaporationevaporate
Relate evaporation to the consequent
cooling
• To change state to a gas the molecules in the liquid
need more heat energy
• When the molecules escape and the liquid evaporates
heat energy is taken from the surroundings
• This cools the surroundings
• eg water evaporating from your skin cools the skin
• Take two thermometers wrap one in dry cotton wool
and the other in wet cotton wool
• Compare the temperatures after a while
Melting and boiling
Describe melting and boiling in terms of energy input
without a change in temperature.
• When a substance melts or
boils it has to take in heat
energy
• When this change of state
occurs there is NO change in
temperature
•
http://en.wikipedia.org/wiki/Melting#Thermodynami
cs_of_melting
State the meaning of melting point
and boiling point.
• http://www.harcourtschool.com/activity/hotp
late/index.html
• Melting point is the point at which a
substance changes from a solid to a liquid
• Boiling point is the point at which a liquid
turns to a gas
Melting
• When a substance melts, some of the attractive
forces holding the particles together are broken or
loosened
• so that the particles can move freely around each
other but are still close together.
• The stronger these forces are, the more energy is
needed to overcome them
• and the higher the melting temperature
Boiling
• When a substance boils, most of the
remaining attractive forces are broken so the
particles can move freely and far apart.
• The stronger the attractive forces are, the
more energy is needed to overcome them
• and the higher the boiling temperature.
Use the terms latent heat of vaporisation and latent
heat of fusion and give a molecular interpretation of
latent heat.
• The energy required to change the state of a
substance is known as a latent heat.
• The word latent means hidden.
• When the state change is from solid to liquid
• we must use the latent heat of fusion, and
• when the state change is from liquid to a gas,
• we must use the latent heat of vaporisation.
Distinguish between boiling and
evaporation
• http://www.vtaide.com/png/boiling.htm
Evaporation vs Boiling
• Ordinary evaporation is a surface phenomenon
• The pressure inside the liquid is equal to
atmospheric pressure
• Therefore bubbles of water vapour cannot form
inside the liquid.
• But at the boiling point bubbles of water vapour
form inside the liquid
• The vaporization becomes a volume phenomena.
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