NS 5: MATTER AND FORCES

 

Unit 7: matter and forces

      7.1 Matter and its properties.

      7.2 Forces and their effects.

      7.3 A new world  of materials.

7.1 Matter and its properties.

- Matter is everything around us and it is made up of atoms and molecules.

- It has got three states: solid, liquid and gas.

- It has got  common properties such as colour, odour and taste.

- Other important properties are: volumen, density, mass, hardness and solubility.

- According to the composition we can classify matter into two types:

·     Pure substances.- It consists of only one type of matter. Example: salt or silver.

·     Mixtures.- They are made up of two or more substances. They can be:

-       Homogeneous mixture.- We cannot see individual subtances. Example: sea water.

-       Heterogeneous mixture.- We can see individual substances. Example: salad. 

-There are different methods to separate mixtures such as: filtration and evaporation.

7.2Forces and their effects.

-A force is a push or pull that acts on an object.

- We cannot see forces, just their effects. There are two types of forces:

·     Non-contact forces.- They act from a distance. The most important ones are: magnetism and gravity.

·     Contact forces.- Thet act through physical contact. The most important ones are: friction and buoyancy.

-Depending on their density some objects sink and other float.

7.3A new world  of materials 

-We can find natural materials and man-made materials.

·     Natural materials.- We can find the in the nature. Examples: Wood and gold.

·  Man-made materials.- They are made by men. Example: steel  and ceramic material.