Unit 6: Matter. Science 6º

Unit 6: Matter

1.- Physical changes.

2.- Chemical changes

3.- Separating mixtures

1.- Physical changes

                            - Change in state.

                            - Change in shape.

                            - Change in positition or texture.

                            - Types of physical changes.

                            - Mass, volume and density.

1.1 Change in state

- We can see water in three states:

                            - Solid.- Example: ice. The atoms are packed together.

- Liquid.- water we drink. The atoms move around each other.

- Gas.- water when is heating. The atoms are opened each other.

1.2 Change in shape

- When we cut the wood, fold a piece of paper or break a glass.

1.3 Change in position or texture.

- Matter can change its position without changing its properties.

- Matter can also change its texture.

1.4.- Types of physical changes

- Reversible.- They come back again. Example: chocolate and juice can be liquid. Then solid freezing and liquid again when it is heating.

- Irreversible.- They are permanent. Example: if we cut bread, we cannot put the slices back  again.

1.5.- Mass, volume and density

·        Mass.- It is the amount of matter in an object. We can measure the mass in grams( g) and kilograms. ( Kg).

·        Volume.- It is the space an object occupies. We measure volume  in millimitres (ml) and litres ( l ).

·        Density.- It is calculated by dividing the mass of an object by its volume.

2.- Chemical changes

- When we are talking about chemical changes, we can find: combustion, oxidation and fermentation.

2.1.- Combustion

- It is a chemical reaction that produces energy on the form of heat and light.

- It happens when oxygen rects with fuels such as wood, gas and oil. The process is called burning.

- When the fuels are burning constitute new substances such as ash and smoke.

2.2.- Oxidation

- It is produced when some  metals react with the air.

- The atoms are changed into a new substance.

- This substance is called rust and it is brown. Then, the oxidation is produced.

2.3.- Fermetation

- Fermetation is the chemical reaction in fungi and bacteria.

- During the fermentation fungi produce alchohol and bacteria produce lactic. Oxigen does not take part.

- Fermetation is used to make food ( cheese and bread) and drinks( wine).

- Fermetation is also used to preserve food such as vegetable, fruits and fish.

3.- Separating mixtures

                                 - Magnetic separation

                                      - Decantation.

                                      - Filtration.

                                      - Evaporation.

                                      - Distilation.

3.0 Introduction

- There are two types of mixtures: heterogeneous and homogeneous.

·        Heterogeneous.- We can see the individual substances and they are easy to separate.

·        Homogeneous.- We cannot see the individual substances and it is difficult to separate.

3.1.- Magnetic separation

- Magnets attract certain types of metals.

- We can use magnets for magnetic separations.

3.2.- Decantation

- Heavy sediments in liquids are at the bottom.

- When we separate the water and the heavy sediments, we are using decantation method.

- We can use decantation as well with two liquids such as water and oil.

3.3.- Filtration

- Filtration separate small particles from a liquid or gas.

- A filter is used to catch the particles but allows the liquid to pass.

3.4.- Evaporation

-  It is the process where a liquid is turning into vapour.

- Evaporation happens as well when the Sun heat the water of the rivers, oceans and seas.

3.5.- Distillation

- It is the process where two liquids, such as water and ethanol, evaporate together but at a different rate.

- We can divide these two types of gas by the distillation process.

- Distillation is used to produce alchohol.