Particulate Model of Matter
Jan 19, 2016
Particulate Model of MatterParticulate Model of Matter
22.1 What Matter is Made Up of
• What is matter made up of?
• Ancient Greek philosophers thought that matter was made up of fire, air, earth and water.
• However, scientists today have deduced from experiments that matter is made up of tiny particles that are in constant and random motion.
22.2 Evidence for Moving Particles
• The spreading of smells, such as from cooking or perfumes, is because of the movement of tiny particles in air.
• These particles move about randomly in all directions, and hence the smells spread.
• We say that diffusion has taken place.• Diffusion is a process by which particles of
matter move from a region of higher concentration to a region of lower concentration.
Experiment 1: Diffusion in Gases
Prepare a gas jar of bromine vapour by placing a few drops of liquid bromine in the gas jar. Then invert a gas jar containing air over it. Observe what happens.
After some time, both gas jars become filled uniformly with a reddish-brown colouration.
22.2 Evidence for Moving Particles
22.2 Evidence for Moving Particles
• Diffusion also occurs in liquids.
• However, it takes place more slowly than in gases.
• This shows that particles in a liquid move around more slowly than in gases.
Experiment 2: Diffusion in LiquidsPlace a few crystals of potassium permanganate at the bottom of a beaker of water. Leave the set-up to stand and observe it from time to time.
After a few days, the purple colouration of potassium permanganate will spread throughout the mixture.
22.2 Evidence for Moving Particles
water
potassium permanganate crystals At the
beginningAfter a few days
22.3 Particulate Model of Matter
Property Solids Liquids GasesShape • Have fixed
shapes• Have no fixed
shapes• Take the
shape of their containers
• Have no fixed shape
• Take the shape of their containers
Volume • Have fixed volumes
• Have fixed volumes
• Have no fixed volume
• Fill up the space of their containers
Compressibility • Cannot be compressed
• Cannot be compressed
• Can be compressed
22.3 Particulate Model of Matter
• Scientists use the particulate model of matter to explain that the three states of matter are different because of the differences in the movement (motion) and arrangement of the particles.
• We can use the particulate model to explain why the behaviour of solids, liquids and gases differs form one another.
Particulate model of solids
• The particles in the solid state:o are strongly attracted to each othero are packed very closely togethero are arranged in a fixed, regular pattern; and o can only vibrate about their fixed positions.
Particulate model of solids
• The particles in a solid are unable to move freely. Thus, a solid has a definite shape and volume.
• There is no space between the particles to enable them to get any closer to one another. This is why solids cannot be compressed.
Particulate model of liquids
• The particles in the liquid state:o are attracted to one another;o are packed closely together;o are not arranged in a fixed, regular pattern; and o can move over short distances.
Particulate model of liquids
• The particles in the liquid state are farther away from one another than the particles in a solid.
• However, the particles in a liquid are still held closely together.
• Thus, like solids, liquids have a fixed volume and cannot be compressed.
• Unlike solids, the particles in a liquid are not fixed in regular positions and are able to slide past one another. This is why a liquid has no definite shape.
Particulate model of gases
• The particles in the gaseous state:o are weakly attracted to one anothero are far apart from one another; ando can move freely in any direction.
Particulate model of gases
• The particles in a gas are spaced far apart from one another and so a gas can be compressed easily.
• The particles are also able to move freely to occupy any available space.
• This explains why a gas has no definite shape or volume.
22.4 Changes of States of Matter
• Matter can exist in the solid, liquid or gaseous state, depending on its temperature and atmospheric pressure.
• At a fixed pressure, the temperature of an object will determine its state.
Boiling occurs when ice is heated to a temperature of 0 0C and above.
Boiling occurs when liquid water is heated to a temperature of 100 0C.
Freezing occurs when water is cooled to 0 0C and below.
Condensation occurs when water vapour is cooled to a temperature of 100 0C and below.
Melting
• When a solid is strongly heated, the particles gain energy and vibrate more vigorously in their fixed positions.
• When the particles have enough energy (i.e. reach the melting point), they break free from one another and move about randomly.
• The particles are no longer held in fixed positions, but they are still close to one another.
• This change in arrangement and motion of particles is known as melting.
Solid LiquidGain in energy
Freezing
• When a liquid is cooled, the particles lose energy and they move about more slowly.
• As the temperature falls, the particles lose more and more energy until they are close enough to allow the forces of attraction to make them return to their fixed positions.
• The substance has changed from a liquid to a solid.• This change in arrangement and motion of particles is
called freezing.
Liquid Solid
Loss in energy
Boiling• When a liquid is heated, the particles gain energy
and vibrate and move about more vigorously. • When the particles have enough energy (i.e reach
the boiling point), they break free from one another.
• The particles become randomly arranged, very far apart and moving about at great speeds.
• This change in arrangement and motion of the particles is known as boiling.
Liquid GasGain in energy
Condensation
• When a gas is cooled, the particles lose energy and they move about less vigorously and at lower speeds.
• As the temperature falls, the particles lose more and more energy until they are close enough to be attracted to one another.
• The substance has turned from a gas to a liquid.• This change in arrangement and motion of particles is
known as condensation.
Gas Liquid
Loss in energy
Miscellaneous
• http://www.bbc.co.uk/schools/ks3bitesize/science/chemistry/particle_model_intro.shtml
• http://www.chem4kids.com/files/matter_intro.html
• http://www.abpischools.org.uk/resources/solids-liquids-gases/slg2.asp
• http://www.chem.purdue.edu/gchelp/liquids/character.html