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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.