Author: jmcminn

Year 5
Term 3

Where would we be without water?
Properties of everyday materials

In this unit the children will:
Compare and group together everyday materials on the basis of their properties, including hardness, solubility, transparency, conductivity (electrical and thermal), and response to magnets
Know that some materials will dissolve in liquid to form a solution, and describe how to recover a substance from a solution
Use knowledge of solids, liquids and gases to decide how mixtures might be separated, including through filtering, sieving and evaporating
Give reasons, based on evidence from comparative and fair tests, for the particular uses of everyday materials, including metals, wood and plastic
Demonstrate that dissolving, mixing and changes of state are reversible changes
Explain that some changes result in the formation of new materials, and that this kind of change is not usually reversible, including changes associated with burning and the action of acid on bicarbonate of soda
Plan different types of scientific enquiries to answer questions, including recognising and controlling variables where necessary

Key Vocabulary
Organic materials - materials derived from living organisms
Natural materials - a natural material that comes from living things or from the ground
Man-made materials - a material that is created by humans and isn’t naturally occurring
Weathering - the breakdown of materials due to long expose to the atmosphere
Decay - the rotting or decomposing of organic matter due to the action of bacteria and fungi
Durability - the ability to withstand wear, pressure or damage
Malleable - the ability for a material to be forced into shape without it breaking or cracking
Brittle - hard but breaks easily
Reversible changes - changes that can be undone or reversed
Irreversible changes - changes that cannot be changed back again, resulting in the formation of a new material
Evaporating - to change a liquid into a gas by heating
Filtering - to pass a mixture through a filter paper to remove undissolved substances
Sieving - to remove larger particles from a mixture by passing it through a sieve
Melting - to turn a solid into a liquid using heat
Dissolving - to incorporate a solid into a liquid to form a solution
Suspension - a mixture of solids particles that do not dissolve in a liquid
Solution - a mixture of a liquid and a solid that has been dissolved in the liquid
Solubility - the ability to be dissolved in a liquid, especially water
Electrical conductivity - the ability to conduct an electrical current
Thermal conductivity - the rate at which heat passes through a material

Key Knowledge
Speciﬁc properties make different materials suitable for particular uses. Scientists continue working on developing new materials and modifying existing ones to improve their properties. E.g. ‘non-sticky’ glue was developed by Spencer Silver and used in ‘Post it’ notes, and properties of ‘super absorbent’ powders and gels have been improved for use eg. in babies’ nappies.
Manufacturers select materials for products dependent upon their properties and durability. Most materials have more than one property and can be natural, man-made, strong, weak, heavy, light in weight, rough, smooth, shiny, dull, hard, soft, flexible, brittle, magnetic, non-magnetic, transparent, opaque, electrical conductor, electrical insulator, conductor of heat, thermal (heat) insulator, burn when heated, does not burn, melt easily or not melt easily.
Materials can be natural or man-made. Many materials show signs of ‘wear and tear’ over time which is something that needs to be considered when choosing which material to use for a product. ‘Wear and tear’ may be due to weathering or regular use (or abuse). Organic materials, for example wood, will decompose (rot) once the surface seal or varnish is broken, whereas some plastics start to break down and can become brittle. Metals that contain iron (eg steel) rust when they are exposed to water and oxygen.
Thermal properties of materials
A thermal insulator is a material that provides high resistance to heat flow, for example, types of foamed plastics like polystyrene, wood, some fabrics and cork. Polystyrene is a very good thermal insulator and is able to keep cool things cool and hot things hot. It has the added advantage of being resistant to moisture, mould and mildew. It is frequently used in cool bags.
https://www.bbc.co.uk/bitesize/topics/zryycdm
Changing Materials
All materials exist in one of the three states of matter; a solid, liquid or gas, at room temperature.
Materials can be changed, these changes can be reversible or irreversible.
Irreversible changes
A change can be irreversible if it cannot be changed back again.
In irreversible changes new materials are always formed. Sometimes the new materials are useful to us.
Heating
Heating can cause an irreversible change. For example you heat a raw egg to cook it. The cooked egg cannot be changed back to a raw egg again.

Mixing
Mixing substances can cause an irreversible change. For example, when vinegar and bicarbonate of soda are mixed, the mixture changes and lots of bubbles of carbon dioxide are made. These bubbles and the liquid mixture left behind, cannot be turned back into vinegar and bicarbonate of soda again.
Burning
Burning is an example of an irreversible change. When you burn wood you get ash and smoke. You cannot change the ash and smoke back to wood again.
https://www.bbc.co.uk/bitesize/topics/zcvv4wx/articles/z9brcwx
Reversible changes
A reversible change is a change that can be undone or reversed.
If you can get back the substances you started the reaction with, that's a reversible reaction.
A reversible change might change how a material looks or feels, but it doesn't create new materials.
Examples of reversible reactions include dissolving, evaporation, melting and freezing.
Dissolving
Some substances dissolve when you mix them with a liquid eg water
When a substance dissolves, it might look like it has disappeared, but in fact it has just mixed with the liquid to form a solution.
Substances that dissolve in water are called soluble substances. When you mix sugar with water, the sugar dissolves to make a transparent solution. Salt is soluble in water too.
Substances that do not dissolve in water are called insoluble substances. When you mix sand or flour with water, they do not dissolve but instead form a suspension. In a suspension, very small pieces of solid are spread through a liquid but do not dissolve. If left still, the solid pieces will separate from the liquid and either fall to the bottom or rise to the top. Sand in water is a suspension.
Heat can help some substances dissolve faster in water. Salt, for example, will dissolve quicker in hot water than in cold water.
https://www.bbc.co.uk/bitesize/topics/zjty4wx/articles/zpbdpbk

Separation
Mixtures can be separated by methods like sieving, filtering and evaporating.
Sieving
A mixture made of solid particles of different sizes, for example sand and gravel, can be separated by sieving.
Filtering
You can separate a mixture of sand and water by passing it through a piece of filter paper. The water is able to pass through the tiny gaps in the paper but the sand particles are too big and are left on the surface of the filter paper.
If salt was also added to the mixture salt water would pass through the filter paper because the salt would be dissolved in the water.
Evaporating
By dissolving salt in water you make a solution. You can separate the salt from the water again by boiling the solution. The water will evaporate until it is all gone. The salt will be left behind.