WATER 1º THE MOLECULE 2º PHYSICAL PROPERTIES 3º STATES OF WATER 4º THE UNIVERSAL SOLVENT 5º SEPARATION TECHNIQUES

1. MOLECULE OF WATER O H A molecule of water has one atom of Oxygen and two atoms of Hydrogen.

The chemical formula of water is 1. MOLECULE OF WATER The chemical formula of water is H2O

That’s a very small number. Isn't it? 1. MOLECULE OF WATER 3 10-23 g 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?

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

The density of liquid water is 1 gram per cubic centimetre. 2. PHYSICAL PROPERTIES 1 g 1 cm The density of liquid water is 1 gram per cubic centimetre. d = 1 g cm3

2. PHYSICAL PROPERTIES The ice floats above the water The density of liquid water is higher than the density of ice (frozen water). The ice floats above the water

2. PHYSICAL PROPERTIES Ice and liquid water can be together at 0 ºC. 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 Why do you think a solid has got a fixed form? Molecules are strongly united Molecules are perfectly ordered Molecules can’t move 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 Molecules are strongly united Molecules are disordered Molecules form small groups 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 Why do you think a gas hasn’t got a definite form? Gaseous Molecules aren’t united There isn’t any force between them Molecules are totally disordered 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 Changes of states Sublimation Fusion Vaporisation Solidification Condensation SOLID LIQUID GASEOSOUS Sublimation 0 ºC 100 ºC TEMPERATURE

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.

Solute + Solvent = Solution 4. THE UNIVERSAL SOLVENT Solute + Solvent = Solution + = Salt Water Salted water A solution is a homogeneous mixture. The most abundant part is called the solvent, and the less abundant part is called the solute.

Salt before being mixed 4. THE UNIVERSAL SOLVENT + How a salt is dissolved in water Salt after being mixed Salt before being mixed + 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.

5. SEPARATION TECHNIQUES Filtration 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 Funnel Beaker

5. SEPARATION TECHNIQUES Decantation stopper Separating funnel 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 Oil Water tap

5. SEPARATION TECHNIQUES Crystallization The solution is heated by the sun Water is evaporated Finally, we can see crystallized salt in the crystallizer Evaporation Crystallizer Aqueous solution Salt

5. SEPARATION TECHNIQUES Distillation 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 Thermometer Clamp Distillation flask Condenser Cooling water Condensed alcohol Steam Ethyl alcohol and water Cold water Receiving flask Bunsen burner Distilled alcohol Clamp stand