1º THE MOLECULE

2º PHYSICAL PROPERTIES

3º STATES OF WATER

4º THE UNIVERSAL SOLVENT

5º SEPARATION TECHNIQUES

WATER

1. MOLECULE OF WATER

O

HH

A molecule of water has one atom of Oxygen and two atoms of Hydrogen.

H2O

The chemical formula of water is

1. MOLECULE OF WATER

One molecule of water has got a very small mass of 0.000 000 000 000 000 000 000 03 g.

That’s a very small number. Isn't it?

3 10-23 g

1. MOLECULE OF WATER

When we drink a glass of water (240g), we are drinking 8,000,000,000,000,000,000,000,000 molecules of water.

That's a very big number. Isn't it?

1. MOLECULE OF WATER

2. PHYSICAL PROPERTIES

The density of liquid water is 1 gram per cubic centimetre.

d = 1 g

cm3

1 g

1 cm

1 cm

1 cm

2. PHYSICAL PROPERTIES

The density of liquid water is higher than the density of ice (frozen water).

The ice floats above the water

2. PHYSICAL PROPERTIES

The fusion point of water is 0 ºC (zero degrees Celsius).

Ice and liquid water can be together at 0 ºC.

2. PHYSICAL PROPERTIES

The boiling point of water is 100 ºC (one hundred degrees Celsius).

Liquid water and water vapor can be together at 100 ºC.

3. STATES OF WATER

Solid

1. Molecules are strongly united

2. Molecules are perfectly ordered

3. Molecules can’t move

4. All molecules form a crystal structure

Why do you think a solid has got a fixed form?

Why do you think it’s very difficult to compress a solid?

3. STATES OF WATER

Liquid

1. Molecules are strongly united

2. Molecules are disordered

3. Molecules form small groups

4. These groups can move among themselves

Why do you think a liquid hasn’t got a definite form?

Why do you think it’s very difficult to compress a liquid?

3. STATES OF WATER

Gaseous

1. Molecules aren’t united

2. There isn’t any force between them

3. Molecules are totally disordered

4. Molecules can move freely in all directions

Why do you think a gas hasn’t got a definite form?

Why do you think it’s very easy to compress a gas?

3. STATES OF WATER

VaporisationFusion

Solidification

Sublimation

Sublimation

Condensation

SOLID LIQUID GASEOSOUS

0 ºC 100 ºCTEMPERATURE

Changes of states

4. THE UNIVERSAL SOLVENT

Water is the universal solvent. In nature we can find water in the seas, rivers, subterranean… and water always contains many other substances.Living beings, drinks, foods, and chemical products are formed by water.

4. THE UNIVERSAL SOLVENT

A solution is a homogeneous mixture. The most abundant part is called the solvent, and the less abundant part is called the solute.

Salt Water Salted water

+ =

Solute + Solvent = Solution

4. THE UNIVERSAL SOLVENT

The molecules of water capture the ions of the salt. Later, all the molecules of salt are mixed among the molecules of water. The crystal structure of salt is destroyed.

++

++

++

++

Salt before being mixed

+

++

+

+

++

+

How a salt is dissolved in water

Salt after being mixed

5. SEPARATION TECHNIQUES

Filtration

Beaker

Funnel

Filter

We use this technique to separate dissolved particles in water

We put a paper filter in a funnel

If particles have a size bigger than the porous of the paper filter, they won’t be able to pass through them

Clean water can pass and fall down into a beaker

5. SEPARATION TECHNIQUES

Decantation

Oil

Water

Separating funnel

tap

stopper

We use this technique to separate two immiscible liquids.

Oil, less dense, is above water

Opening the tap, water is falling down, drip-drop

When oil is going to escape we turn off the tap

5. SEPARATION TECHNIQUES

Crystallization

Crystallizer

Aqueous solution

Salt

Evaporation

The solution is heated by the sun

Water is evaporated

Finally, we can see crystallized salt in the crystallizer

Distillation

5. SEPARATION TECHNIQUES

Clamp stand

Bunsen burner

Ethyl alcohol and water

Steam

Clamp Thermometer

Distillation flask

Condenser

Cooling water

Condensed alcohol

Cold water

Receiving flask

Distilled alcohol

We use this technique to separate mixed liquids

We heat the mixture in a distillation flask

At 78 ºC ethyl alcohol is boiling and it escapes from the flask

Alcohol is condensed into the refrigerator tube

Finally we have distilled alcohol in an Erlenmeyer flask