CHE1: MIXTURE S.1

MIXTURE

What is a mixture?

A mixture is a combination of two or more substances that are not chemically combined.

Give examples of mixtures (e.g from home)

Sugar, salt and water mixture

Iron filling, salt and sugar mixture

Are mixture are impure substances

Mixtures are impure substances

How do we get pure substances from mixture?

The following are examples of getting pure substances:

• Winnowing
• Sorting
• Crystallization
• Decantation

Pot method

• Magnetism decantation
• filtration
• sieving

Experiment:

Aim

To get pure common salt from a mixture of salt and soil/sand

Method:

Describe the produce as follows:

Water was added to the mixture of salt and until it dissolved. The water with salt was filtered from the sand using filtration paper. Then the water and salt mixture was boiling to evaporation.

Observation:

The water evaporated and the soil remained at the bottom of container. The soil stayed on the filtration paper.

Explanation

Common salt dissolves in water but soil is in soluble in water, when the mixture was added to water and stirred, the solution containing on the dissolved salt and remaining on the filter papers as the residue. The solute in the filtered crystallized when the solvent evaporated.

NB

The solution of salt in water contained salt as a solute and water as a solvent.

Conclusion

This method is used to separate a mixture of 2 solids, one of which is soluble in a a solvent (e.g. water)

Diagram of a condenser

• To get pure water from salty water

• To get pure water from salty, the apparatus is set up as the diagram. The salty water is heated in the flask. The solvent vaporizes and condensers in the lie big condenser. The distillate is received in a beaker or test tube.

Observation

What does the liquid in the flask taste like?

It is salty

What does distillate taste like?

Tasteless

Supposing the liquid in flask is heated to dryness, what would be seen in the flask?

White crystal

Conclusion

This method of getting pure water from salty water is called simply distillation. It can be used to get a pure solvent from its solution.

How does the lie big condenser work?

It cools a vapor until it turns into a liquid

Exercise

Using simple English show what you understand by the terms;-

Mixture

A combination of two or more substances that are not chemically combined

Solution

Is a uniform/homogeneous two substances mixture of a solute and a solvent?

Solute

Is a solid, gas, liquid that can be added into a solvent to form a solution, e.g. chalk? Is a substance (solid) that can mix in any solvent?

Solvent

Is a liquid into which a solute is added dissolves to form solution e.g. water?

Suspension

A liquid that contains small particles of a solid which are spread throughout a liquid and get settled on standing solids particles that don’t dissolve

Filtration

Is what is got in container after filtration has been done the liquid obtained after filtration?

Distillate

Is that result got after distillation done?

Residue

This is what remains in the server or filtrate paper after filtration

To separate a mixture of liquids that:

Mix uniformly e.g. water + ethanol when a homogenous mixture is formed, we say water and ethanol are miscible

The apparatus is set up as follows

Diagram of a condenser

Observation

The mixture of ethanol and water did not burn it was lit. But when the distillate was lit it burnt. The distillate burnt with a blue flame

Which of the two substances in a mixture burns with a blue flame?

Ethanol burns with a blue flame

Name the distillate.

Ethanol

How does a fractionating works.

When the mixture of water is heated, both the water and ethanol evaporate. In the column, water condenses and flows back into the flask. But the ethanol vapor continues rising into the lie big condenser, where it is condensed.

To make sure the column works properly, the temperature at point X trust be maintain at the boiling point of ethanol at about 78^oc.

Conclusion

This method of separating liquid mixtures is called fractional distillation. It only works if the liquids have different boiling point. (Industrial)

Application                    

Distillation of crude petroleum

For example:

Diesel, kerosene

Do not mix uniformly

They are heterogeneous mixture/immiscible mixtures

-When immiscible liquids are poured in to the separating funnel the form separate layers

-When the top is opened, the denser liquid pours off first. When it is drained off, the top is closed, and then the less dense liquid can be poured into separated beaker

How to separate a mixture of solids both of which are soluble in a common solvent

THIS VIDEO EXPLAINS MORE ABOUT MIXTURES