UNIT 3 MATTER

MATTER

What ismatter?

Definition

- Matter is everything that exists, has mass and occupies space (oxygen, tables, orange juice...). - Matter has volume and mass. - It can be found solid, liquid or gas. - Matter is formed by atoms and atoms form molecules.

Classification of matter:

Pure substances:

Mixtures:

2 or more pure substances.

Homogeneous

Heterogeneous

Only consist of one type of matter. Ex: silver.

VOLUME, MASS AND WEIGHT

They are common to all matter, but they don´t help us to identify the type of matter.

Volume

Weight

Mass

Amount of space that occupies. Litres (l).

Amount of matter in an object. Grams (g).

Measure of the amount of gravity on matter. Gravity in space is almost zero.

How can weidentify matter?

Properties of matter:

Elasticity

Colour

Hardness

This is the ability of a solid object or substance to return to its original shape after removing the force which deformed it.

Objects or substances can be different colours or different shades of colour.

It is the measure of how resistant to pressure or scratching an object is.

Magnetic properties

Density

This is the amount of mass per unit of volume in an object. density = mass/ volume It is a measure of how tightly packed the molecules are. Every object has its own density. Density measured in kg/l (kilograms per litre).

It is the ability of certain substances to attract metals.

Melting point

Boiling point

Solubility

This is the ability of a substance to dissolve in another substance and form a solution.

• If a substance dissolves well in another substance, it is soluble.

• If a substance does not dissolve well in another substance, it is insoluble.

When the temperature of an object or substance increases, it can reach melting point. This is the temperature at which a solid changes to a liquid.

When the temperature of a liquid increases, it can reach boiling point. This is the temperature at which a liquid changes to a gas.

Electrical conductivity

Thermal conductivity

This is the ability to conduct electrical current through it.

• Some materials, such as copper, gold and graphite are good electrical conductors.

• Others like glass, cotton and rubber are electrical insulators.

This is the ability to conduct heat.

• Metals, such as copper and iron, are good heat conductors.

• Materials like wood, paper, plastic, glass and wool are heat insulators.

Why do some objects float and others sink?

FLOAT / SINK

FLOAT / SINK

The reason why some objects FLOAT in water (or other liquids) and others SINK is because of:

Density

2 forces

An object is going to FLOAT when its density is lower than the density of the liquid.

An upward force which pushes the object toward the surface.

Buoyancy

If the object is denser than the liquid it will sink. - If the object is less dense than the liquid it will float.

Gravity

A downward force which pushes down the object.

THE AVERAGE DENSITY

But... How can ships or cruises float in water ? They are made of steel and metals, which are denser than the water

Because the average density is what determines whether it floats or sinks. It takes into account: - The steel that the ship is made of. - The air that is trapped in the body of the ship. If an object's average density is less than the water it will float. For example, a cruise ship has a lot of air inside it, and its average density is lower than water so it floats

How do drones and planes fly?

Flying machines fly because of the four forces of flight.

The push that lets the plane move upwards.

Lift

The resistance that air opposes to movement.

The force which forces the plane forwards.

Thrust

Drag

Weight

the force of gravity on the plane.