Properties of matter and materialsChemistryChapter 9

Elements

A substance that has only one kind of atom.

93 elements are natural, while 24 are man made.

Molecules

A substance made of groups of one or more element.

Metals and non-metals

- Scientists divided all the elements into 2 groups: Metals and non-metals

Look at the following pictures and describe some of their properties

Metal Non-metal

Property Metal Non-metalSurface Shiny Dull

Physical state at room temp.

Usually solid Solid, liquid or gas

Strength Shaped by pressing and stretching

without breaking easily

Soft or brittle

Melting point Usually high Usually lowBoiling point Usually high Usually low

Density Usually high Usually low Conduction of heat Good Very poor

Conduction of electricity

Good Very poor

Non-metal UseChlorine - Purify water (kills

microorganisms)- In swimming pools (keeps the

water clean)Phosphorus - Used on tip of matchesIodine - Used in some portable water

purifying kits (used by people who take adventure holidays)

- Some metals and non-metals are exception to the rules.

Example:- Magnesium (metal), but it has a dull surface.

- Graphite (non-metal), conducts electricity.

- Iodine (non-metal), shiny surface

The properties of materials

- There are a number of properties that materials may have.

1) Surface appearance

- Shiny, dull, rough or smooth

2) Rigid- Cannot be bent or squashed.- Example: Rock

3) Flexible

- Can be bent or squashed.- Example: Flexible piece of

wood (Used as bows)

4) Hard or soft

- Usually hard materials are rigid and soft materials are flexible.

5) Malleable

- Materials that can be shaped by hammering or pressing.

- Example: Gold, silver and copper are malleable

6) Brittle

- Materials that break suddenly when they are bent or hit.

- Example: Biscuit or chocolate bar

7) Absorbent

- Materials have holes in their surface to let the water pass through and have spaces inside where the water can collect.

- Some rocks (sandstone and limestone) have gaps(pores) they are porous.

8) Waterproof

- Materials that do not pass water through.

Water resistant

Water repellent- Made of fibres.

- There are holes between the fibres (water passes through)

- Fibres are coated with silicones (does not allow water to be absorbed)

- Used to make: Umbrellas, outdoor jackets and trousers

- Do not have any holes in it through which water can pass

- Used to make: Wellington boots

9) Transparent

10) Translucent

11) Opaque

- Lets light pass through it (can see objects clearly through it).

- Lets some of the light pass through

- Do not let the light pass through

12) Heat conductor

13) Heat insulator

- Allows heat to pass through

- Does not allow heat to pass through

14) Electrical conductor

15) Electrical insulator

- Allows electricity to pass through

- Does not allow electricity to pass through

Property profile

- A description of a material in term of its properties is called a property profile.