Solutions

 

Solutions are mixtures that are homogeneous.

( same throughout)

 

For example sugar mixed with water.

 

A solution forms when one substance dissolves in another. There cannot be a solution without dissolving.

 

The substance that dissolves is called the solute.

The substance that does the dissolving is called the solvent.

 

For example when you mix sugar and water the solute is the sugar and the solvent is the water.

 

The substance present in the most amount is always the solvent. For example air is a solution- the solvent is Nitrogen which makes up 78% of air and oxygen is a solute.

 

Some Examples

 

Solution                  solute                     solvent

 

Kool-aid        Kool-aid ( solid)             water ( liquid)

Pepsi           carbon dioxide ( gas)        water ( liquid)

air                 oxygen ( gas)                  nitrogen ( gas)

Bronze         zinc ( solid)                     copper ( solid)

mixed gas   motor oil ( liquid)             gasoline ( liquid)

 

A substance that is able to dissolve in a solvent is called soluble. For example: sugar, salt, vinegar, motor oil, oxygen

 

A substance that is unable to dissolve in a solvent is called insoluble. For example rock, wood, sand,glass, iron

 

Some substances are soluble in one substance but insoluble in others. For example:

 

- motor oil will not dissolve in water but will dissolve in gasoline

- chlorophyll will not dissolve in water but will dissolve in rubbing alcohol.

 

Dissolving/ Particle Theory

 

The particles in a substance are attracted to one another. This is what keeps a substance together.

 

If you put a substance in water, there is attraction between the water particles and the particles in the substance.

 

- if the attraction between the particles of the substance are stronger then the attraction between the particles and the water particles - the substance will not dissolve.For example if we put sand in water, the attraction between the sand particles are stronger then the attraction between the water and sand particles so the sand will not dissolve

 

- if the attraction between the particles of a substance are not as strong as the attraction between the particles and the water particles. the substance will dissolve. For example if we put sugar in water, the attraction between the sugar particles are not stronger then the attraction between the water and sugar particles so the sugar will dissolve.

 

Solubility

When we make a solution, the amount of solute and solvent determines the solutions concentration.

 

If we have a solution with a lot of solute and a little solvent, then the solution is concentrated. This type of solution is often a dark color and we might call it "strong." For example: if we put a lot of kool-aid powder in a little water we would get a concentrated( strong) solution of kool-aid.

 

If we have a solution with a little solute and a lot of solvent, then the solution is dilute. This type of solution is usually lighter colored and we would call it "weak." For example: If we put only a little kool-aid powder in a lot of water we would get a dilute( weak) solution of kool-aid.

 

The amount of solute mixed with a certain amount of solvent is a solutions concentration. For example 5 grams of sugar in 1 liter of water makes a solution with a concentration of 5g/L.

 

This way of expressing concentration is called quantitative ( with numbers).

 

We can also express concentration qualitatively ( with words) such as saying dilute or weak.

 

The solubility of some common substances are:

sugar 1792 g/L

salt 357g/L

oxygen 0.07g/L

 

The rate of dissolving

 

The time it takes a solute to dissolve depends on several factors.

 

- The size of the particles. The more surface area the faster the solute dissolves.

 

- The temperature. The higher the temperature the faster a solute will dissolve.

 

- Pressure.. The higher the pressure the faster the solute will dissolve.

 

- Movement of the solvent. If we stir water a solute will dissolve faster.

 

 

There is a limit to how much solute that can be dissolved in a certain amount of solvent. As we dissolve the solute in the solvent we eventually reach a point where no more solute can be dissolved. 
The saturation point is the point where the solvent cannot hold anymore solute.

 

If a solution can dissolve more solute we say it is unsaturated.

 

If a solution cannot dissolve any more solute it is saturated.

 

The saturation point is where a solution goes from unsaturated to saturated.

 

If we increase the temperature and pressure, we
can dissolve more solute than could normally be ?dissolved. We can increase the Saturation Point
For example: rock candy or co2 in pepsi