SOLUTIONS

Unit 3

Solution

It is a homogeneous mixture that is formed when a substance is dissolved in another substance.

Homogeneous VS. Heterogeneous Mixture

A homogeneous mixture is a mixture where the components that make up the mixture are uniformly distributed throughout the mixture.

Homogeneous mixtures: air, blood, saturated sugar water

A heterogeneous mixture is a mixture where the components of the mixture are not uniform or have localized regions with different properties.

Heterogeneous mixtures: rocks, oil and water, soup, pizza

Solute and Solvent

Solute - The dissolved substance

Solvent - The substance that dissolves

Characteristics

Transparent and clear Homogeneous Solute does not

separate from solvent when left to stand on its own

No residue when filtered

Examples

Dilute, Concentrated, Saturated

Serial Dilution Method

Uses of Solute and Solvent

1. Name at least 5 uses for solute and 5 uses for solvent

2. Describe the importance of water as a solvent.

3. Is water a universal solvent?

4. Write in your Science notebook

Solutions

Dilute Concentrated Saturated

Has very little solute

Has a lot of solute

Has the maximum amount of solute in it

Can dissolve a lot more solute

Can dissolve a little bit more solute

Cannot dissolve any more solute

Concentration of a solution

A volume of solution is usually measured in cm³ or dm³

1 dm³ = 1000 cm³ A concentration of a solution is measured in grams

per dm³ (g/dm³). Example: a concentration of 10 g/dm³ means there

are 10 g of solute in every 1000 cm³ of solution To prepare 10 g/dm³ of sodium chloride, you need

to weigh 10 g of sodium chloride and dissolve it in 1000 cm³ of distilled water.

Test Yourself

1. Which are the solvent and solute when salt is added into water to make a salt solution?

2. To prepare 20 g/dm³ of NaCl, how much cm³ of solvent distilled water do you need?

Suspension & Colloid Characteristics

SUSPENSION Heterogeneous mixture Insoluble solids obtained

at the filter paper when filtered

Pushed down to the bottom/does not dissolve

COLLOID Light can reflect

- Particles are large enough to reflect light- Are not affected by gravity (they usually not settle at the bottom)- Heterogeneous (but looks homogeneous)

Which One Has Scattered Light?

Solution Colloid

DISSOLUTION

Solubility gives us a measure of how much solute can dissolve in a solvent

Solubility is the maximum amount of solute in grams that will dissolve in 100 g of solvent at a given temperature

SOLUBILITY

A solvent can only dissolve a certain amount of solute. Solubility gives us a measure of how much solute can dissolve in a solvent.

For example, the solubility of sodium chloride in a water at a temperature of 20ºC is 38 g per 100 g of water. This means that a maximum of 38 g of sodium chloride can dissolved in 100 g of water at 20ºC. The solution produced is a saturated solution.

LAB CHEMICALS

Chemical Name Formula Uses & Other names

sodium chloride NaCl Table salt / common salt

dihydrogen monoxide H₂O Water

glucose C6H12O6 Carbohydrate / simple sugar

potassium nitrate KNO3 Potash, Food preservatives, fertilizers, gun powder

Factors Affecting Solubility

Nature of Solvent Nature of Solute Temperature Pressure

NATURE OF SOLVENT

The solubility of a solute varies in different solvent

NATURE OF SOLUTE

Different solutes have different solubility in a given solvent.

PRESSURE

For solid and liquid solutes, changes in pressure have no effect on the solubility.

For gaseous solutes, an INCREASE in pressure increases the solubility and a DECREASE in pressure decreases the solubility.

PRESSURE AFFECTS GAS SOLUBILITY

For gaseous solutes, an INCREASE in pressure increases the solubility and a DECREASE in pressure decreases the solubility.

RATE OF DISSOLUTION

Temperature of the Solvent Rate of Stirring Size of the Solute Particles

TEMPERATURE OF THE SOLVENT

The higher the temperature of the solvent, the faster the solute dissolves.

RATE OF STIRRING

The faster the stirring is, the faster the solute will dissolve in the solvent.

SIZE OF THE SOLUTE PARTICLES

The smaller the size of the solute particle is, the faster it dissolves in a solvent.

Difference between solubility and dissolution

Dissolution is a kinetic process and is quantified by its rate.

Solubility is the property of a solid, liquid, or gaseous chemical substance called solute to dissolve in a solid, liquid, or gaseous solvent to form a homogeneous solution of the solute in the solvent.