24 properties of matter and materials.

Properties of matter and materialsChemistryChapter 9

Is water an element?

• People believed that water was an element until about 1800.It was only then that a scientist passed electricity through water and found that it split up into two gases (Hydrogen and oxygen).

Review

• Atom : The smallest building unit of matter.• Element : A substance that is made of just one kind of atom.• Molecule : A small group of same type of atoms joining together tightly.• Compound : Group of different atoms joined together tightly.

Elements

A substance that has only one kind of atom.

93 elements are natural, while 24 are man made.

Particle accelerator

• Is an apparatus used to make atoms of new elements by adding particles inside the accelerator and then made to crash into each other.

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 when heated it

catch fire and burns with a brilliant white flame.

- Graphite (non-metal), is form of carbon and used to make pencil ,it conducts electricity .

- Iodine (non-metal), shiny surface and looks ,but it is a non-metal.

Metal alloys

• Metal alloys : mixture of metals.• Bronze is a mixture of copper and tin , used to bells as it makes ringing sound

when struck.• Brass is a mixture of copper and zinc ,it is strong and corrosion resistant.• Steel is mixture of iron ,carbon ,magnesium ,sulfur ,nickel.• Stainless steel is a mixture of steel and chromium , used to make knives ,spoons and kitchen sinks.

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.