UNIT 4 SCIENCE - MATTER

Aquí tenéis la unidad completa número 4 (Materia) con la que estamos trabajando ahora mismo. Os la dejo también en PDF completa, tanto en inglés como en castellano, para que podáis ayudar a vuestros hijos en caso de tener alguna duda, y también para que la puedan descargar, imprimir, o llevar con ellos en tablets, teléfonos móviles u ordenadores. 

PDF de la unidad en inglés                     PDF de la unidad en castellano



Absolutely everything is made of matter. All matter has a mass and a volume. Mass is the amount of matter and volume is the space it occupies. Matter can be natural or man-made and exists in three states: Solid, liquid and gas. By the end of this unit you will understand more about what matter is made of and its different properties.

What is matter?

An atom is the smallest particle of matter. It is extremely small you need a very special microscope to see one.

Scientists have found approximately 100 different types of atoms. Each one has a name and is represented by one or two letters. Oxygen (O), hydrogen (H), carbon (C), gold (Au) and iron (Fe) are examples of atoms.

A molecule is made when two or more different atoms join together. For example, two hydrogen (H) atoms and one oxygen (O) atom join together to make an H2O molecule.

Do you know the name of the substance H2O molecules make?

Pure substances are made from one type of atom or one type of molecule. There are two types of pure substances. Elements are made of atoms, for example, pure gold. Compounds are made from molecules, for example, pure water.

Properties of materials: 

- Hard or soft. Hard materials are very difficult to scratch or cut. Soft materials are cut or scratched easily. A diamond is a hard material. Chalk is a soft material.

- Tough or fragile. Tough materials are very difficult to break. Fragile materials break easily. Steel is a tough material. Glass is a fragile material.

- Plastic or elastic. Plastic materials are easy to bend. Elastic materials go back to their shape after we squash or stretch them. Polythene is a plastic material. Sponge is an elastic material.

Thermal insulators and conductors 

Why is a pan made of metal with a plastic handle? 

The molecules in matter are never still. Sometimes they move slowly and sometimes they move quickly. We can't see this movement but we can feel it as heat. 

At low temperatures, for example in an ice cube. the water molecules move very slowly. We touch the ice cube and it feels cold. 

At high temperatures, for example in a cup of tea, the water molecules move quickly. We touch the cup of tea and it feels hot.

Water is a thermal conductor. Its molecules are free to move about. This means it can get very hot. Glass and metal are thermal conductors too.

Other materials are thermal insulators. Their molecules are close together and can't move about. This means they can't get hot. Plastic and wood are thermal insulators.

Look at the photos. Say which materials are conductors and which are insulators. 

The plastic stops the heat from the metal reaching your hand.	We cook with wooden spoons because they don't get hot.	The metal gets very hot and cooks the egg.	The glass gets very hot and starts a fire.

Mixtures and solutions

When two substances are mixed together they form a mixture. A mixture is not a pure substance. There are two basic types of mixture: a heterogeneous mixture and a homogeneous mixture.

In a heterogeneous mixture we can see the separate substances. This is because their molecules don't mix. 

In a homogeneous mixture we can't see the separate substances. This is because one substance dissolves into the other and their molecules mix. 

A homogeneous mixture is also called a solution. The substance that is dissolveed is called the solute and the substance that dissolves it is called the solvent.

Hot chocolate is an example of a solution. Chocolate powder is the solute and milk is the solvent.

Each chocolate molecule still exists but it is now surrounded by milk molecules.

When you dissolve a solid in a liquid it looks like it disappears. Check the mass to know it is still there. 

Look at these examples of solutes and solvents in everyday life. How do they work? 

Nutrients are solutes	Water is a solvent, shampoo is a solute	Water is a solvent	Nail varnish remover is a solvent

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Changes in matter

Matter can change. There are two types of changes.

In a physical change, the molecules move about but their structure doesn't change.

In a chemical change, new molecules are made and the matter is changed forever. 

Physical changes

We can fold paper and change its shape, but it's still paper.	We can freeze yoghurt and change its state, but it's still yoghurt.	We can fly a nylon kite and change its place, but it's still made of nylon.	We can heat milk and change its temperature, but it's still milk.

Chemical changes 

When an apple rots, new molecules form and make different matter.	When wood burns, new molecules form and make different matter.	When iron rusts, new molecules form and make different matter.	When milk ferments, new molecules form and make different matter.