Model of Matter Summary NotesEverything in the universe is made of matter. Matter is tiny little particles known as atoms, molecules or ions. These particles make everything we see including me and you.

Solids Liquids and gases Solid Liquid Gas

There are 3 states of matter: Solids Liquids Gases

Solids: Have a fixed shape. Have a fixed volume. Cannot be compressed.

Liquids: Have no fixed shape. Have a fixed volume. Can be slightly compressed.

Gases: Have no fixed shape. Have no fixed volume. Can easily be compressed.

DiffusionDiffusion is the movement of particles to fill spaces. Gases have the biggest spaces between particles, so diffusion occurs faster in gases than in liquids. Diffusion does not occur in solids because there is no space for particles to move into.

Changing States of MatterHeating and cooling a substance can cause it to change state.

While a substance goes through a change of state, there is no change of temperature.

This is because: Heat energy is produced when bonds are formed, which happens

during these changes: gas → liquid → solid.

Heat energy is used up when bonds are broken, which happens during these changes: solid → liquid → gas.

The Water CycleWater naturally exists in all 3 states and changes state throughout the Water Cycle.

There are different types of precipitation, including rain, snow and hail.

SolubilityWhen you add sugar to tea it gives it a sweet taste. You can’t see the sugar anymore, but it is still there as you can taste it. The sugar has dissolved. When a substance dissolves, the particles mix with the particles

of the liquid. As sugar dissolves in water to make a solution, sugar is said to be soluble.

In a solution, the substance that is dissolved is called the solute. The solvent is the substance which does the dissolving. When the solute dissolves in the solvent, the mixture produced is called a solution.

A solution containing a lot of sugar is called a concentrated solution. A solution containing a lot of solvent (water) is called a dilute solution. Since the sugar has dissolved it is said to be soluble.

If you put lots of sugar in your cup of tea or coffee, it may not all dissolve. If the solution cannot dissolve more solute it is called a saturated solution. If a substance is not soluble (it doesn’t dissolve) it is insoluble.

Methods of heat energy transfer

Heat can be transferred by conduction, convection and radiation.

Conductors and insulators

Conductors allow heat energy to travel easily through them. Metals and carbon are good conductors. Some metals are better conductors than others and therefore let heat travel from one end to the other quicker than the others. Copper is a good conductor. Insulators are poor conductors of heat energy. They do not let heat energy travel through them easily. Glass, plastic, wood, rubber and air are all good insulators.

Conduction

When heat flows through solids it is known as conduction. It moves from the hot end to the cold end. When a solid substance is heated, its particles gain energy and vibrate more vigorously. The particles bump into nearby particles and make them vibrate more. This is why the handle of a metal spoon soon gets hot when the spoon is put into a hot drink.

ConvectionLiquids and gases are called “fluids”. Heat energy can travel through fluids by convection. The particles in liquids and gases are free to move about. A convection current happens when particles with a lot of heat energy in a liquid or gas move further apart causing the liquid or gas to become less dense as there are spaces between the particles. The less

Heat source

Direction of heat travel

Cold end

dense liquid/gas rises and as it cools the particles move closer and the liquid/gas becomes denser and sinks down. Heat energy is transferred from hot places to cold places by convection currents.

Radiation

All objects transfer heat energy by infrared radiation. The hotter an object is, the more infrared radiation it gives off. Infra-red radiation is often just called radiation, heat rays or simply heat.Infra-red radiation is emitted in all directions in straight lines.

No particles are involved in radiation, unlike conduction and convection. This means that heat energy transfer by radiation can even work in space, but conduction and convection cannot. Space is known as a vacuum as it has not particles in it.

Radiation is the reason we can feel the heat of the Sun, even though it is millions of kilometres away in space.

Depending on the position of the heat source we can set up single or double convection currents as shown in these two diagrams.

Colour and Radiation

All hot objects radiate heat, but some are better than others.Dark, dull surfaces absorb (take in) more heat energy than light, shiny surfaces. Dark, dull surfaces also radiate heat better when they are hot. Light, shiny objects will reflect (bounce) heat energy.

A black car will warm up faster on a hot summer’s day.

Houses are often painted white in warm, sunny countries so that they stay cooler for longer as the white/silvery surface reflects away much of the Sun’s infra-red heat rays.

Insulation

Air is a very good insulator, which means it does not let heat travel through it easily. Trapped air is a very good insulator. This is because there are large gaps between particles making it hard to transfer the heat energy. Trapped air in clothing and blankets help to prevent heat loss. Fur, feathers and hair can also trap air to prevent heat loss.

Reducing heat loss

In our homes we can use double glazing where trapped air between two panes of glass prevents heat escaping by conduction or convection.

We can also use cavity wall insulation which prevents heat loss by conduction. Loft insulation traps air in the fibres and reduces the amount of heat escaping through the roof by convection.

Chemical changes and physical changes

Chemical changes happen when chemical reactions occur. All chemical reactions involve forming a new substance, this is known as a product.

Physical changes do not lead to new chemical substances forming. In a physical change, a substance simply changes physical state, eg from a solid to a liquid.

Physical changes can often be reversed but chemical changes are much more difficult to reverseFor example:Liquid water becoming steam (when water boils) is a physical reaction:

Whereas:Liquid water decomposing into hydrogen and oxygen, eg when an electric current is passed through water, is a chemical reaction:

Controlling the speed of chemical reactionsFor a chemical reaction to happen, particles must collide (crash) with each other. They must collide with enough energy (speed) and at the correct angle to join and form new products.To make a chemical reaction go faster we must make particles collide more often.This can be done by:

Decreasing particle size Increasing temperature Increasing concentration Addition of a catalyst

Particle sizeAs the particle size decrease, the rate of reaction increases.

New substance

s made

This is because as the particle size decreases, the surface area increases. The greater the surface area the more chance particle have of bumping into each other. The more particles bump off each other, the more reactions take place.

TemperatureAs the temperature increases, the rate of reaction increases. This is because temperature is a measure of the energy of particles. As the temperature increases, the particles gain energy and move faster. The faster the particle move, the more likely they are to bump into each other meaning more reactions take place.

ConcentrationConcentration is the measure of how many particles have been dissolved into a solution.As the concentration increases, the rate of reaction increases.As the concentration increases there are more particles present. The more particles there are, the more likely they are to bump into each other meaning more reactions take place.

CatalystsCatalysts increase the rate of a reaction. They take part in the reaction but are not used up. This means they can be used again.If a catalyst is present, the particles can collide more often with less energy and so the reaction can occur at lower temperatures.

Catalysts are used every day. Some examples include

Use of platinum in car exhausts. Platinum is used speed up the reaction turning carbon monoxide (poisonous) into carbon dioxide (not poisonous)

We have chemicals in our bodies that act like catalysts called enzymes. Amylase and Pepsin are two types of enzymes that help to break down our food for digestion