chemistry - separating mixtures

Question 1

Define dissolve.

Answer 1

To mix a solid substance into a liquid so that it becomes part of the liquid and is no longer visible.

Question 2

Define solution.

Answer 2

When one substance (the solute) is completely dissolved in another (the solvent).

Question 3

Define solvent.

Answer 3

Dissolves a solute to form a solution.

Question 4

Define solute.

Answer 4

A solute is a substance that is dissolved in a solvent to form a solution.

Question 5

Define soluble.

Answer 5

The ability of a substance to dissolve in a solvent, typically a liquid.

Question 6

Why do pure substances have a fixed melting point?

Answer 6

All the particles of a pure substance are alike, requiring the same amount of energy to transition from a solid to liquid state.

Question 7

Explain the definition of evaporating.

Answer 7

Evaporation is the process by which a liquid turns into a gas only at the surface and below its boiling point.

Question 8

Explain the definition of boiling.

Answer 8

Boiling is the process in which a liquid turns into a gas (vapor) throughout. This happens when the liquid reaches its boiling point.

Question 9

What effect does salt have on the boiling point of water?

Answer 9

Adding salt to water causes boiling point elevation, meaning the water will boil at a higher temperature than 100°C.

Question 10

What effect does salt have on the melting point of water?

Answer 10

Adding salt to water causes the melting point

Question 11

How can you carry out a simple distillation?

Answer 11

Heat a liquid mixture in a flask until the component with the lowest boiling point evaporates. The vapor passes through a cooled condenser, where it turns back into liquid and is collected in a separate container. The remaining substances with higher boiling points stay behind in the original flask.

Question 12

How can you carry out a fractional distillation?

Answer 12

A mixture of liquids is heated so the one with the lowest boiling point evaporates first. The vapor rises through a fractionating column (which helps separate the components), then condenses in a cooled condenser and is collected, with other liquids collected as the temperature rises.

Question 13

Describe crude oil as a mixture of lots of different compounds.

Answer 13

Crude oil is a complex mixture of many different hydrocarbons and other chemical substances. It contains a wide range of components, including gases like methane, liquids like gasoline, diesel, and kerosene, and solids such as asphalt, all having different boiling points.

Question 14

List the use for these fractions in crude oil: REFINARY GASES, PETROL, NAPHTHA, KEROSENE.

Answer 14

refinary gases: domestic heating+cooking
petrol: fuel for cars
naphtha: chemicals to make plastics
kerosene: fuel for aircraft

Question 15

List the use for these fractions in crude oil: DIESEL OIL, FUEL OIL, LUBRICATING OIL, BITUMEN.

Answer 15

diesel oil: fuel for SOME cars and trains
fuel oil: fuel for power stations
lubricating oil: reduce friction between moving parts
bitumen: road surfaces/roof covering

Question 16

Explain an experiment to purify rock salt.

Answer 16

To purify rock salt, dissolve it in water, then filter out the insoluble impurities. Finally, evaporate the water to leave behind the purified salt crystals.

Question 17

What is chromatography?

Answer 17

A way of finding out whether a liquid is a pure substance or a mixture.

Question 18

What is distillation?

Answer 18

Distillation is a method used to separate liquids based on their boiling points. The mixture is heated until one part evaporates, then the vapor is cooled and condensed back into a liquid and collected separately.

Question 19

How do you use chromatography to investigate different colours of ink?

Answer 19

Place a small ink spot on a pencil line drawn near the bottom of chromatography paper. Put the paper in a beaker with a little water and as the water travels up the paper, it carries the different dyes at different rates.

Question 20

When sand is added to water, the boiling point does not change. Why?

Answer 20

Sand is insoluble and does not dissolve in water unlike salt which is soluble.

Question 21

The white solid is mostly calcium carbonate (chalk). Why does the mineral water contain this?

Answer 21

It is found normally underground or quite low.

Question 22

What is fractional distillation?

Answer 22

It involves the separating of crude oil into lots of different fractions. It uses a tall column order in order to produce many temperatures. Hotter towards bottom.

Question 23

What does hydrocarbon contain?

Answer 23

Carbon and Hydrogen.

Question 24

What happens if a hydrocarbon has a higher boiling point?

Answer 24

It will exit the fractional column at a lower level.

Question 25

How many carbons is Methane made out of?

Answer 25

1 carbon.

Question 26

How many carbons is Hexane made out of?

Answer 26

Six carbons.

Question 27

Sally wants to separate a mixture of salt and sand. How?

Answer 27

Add water to the mixture, filter the mixture, the sand should collect in the filter paper. Lastly, evaporate the solution to collect the salt crystals.

Question 28

What is the role of the apparatus called a condenser.

Answer 28

Allows the filtrate to condense inside it so it can then have the water to drip in the conical flask.

Question 29

Which processes occur during distillation?

Answer 29

Evaporation then condensation.

Question 30

What should the line where the ink spots are placed to be drawn with in chromatography? Why?

Answer 30

Pencil so that it won't be brought up along with the dots.

Question 31

Which separation technique can obtain sand from a mixture of sand and sea water?

Answer 31

Filtration.

Question 32

Which separation technique can obtain diesel oil from crude oil?

Answer 32

Fractional distillation.

Question 33

Which separation technique can obtain pure water from salt solution?

Answer 33

Distillation.

Question 34

Which separation technique can obtain salt from salt solution?

Answer 34

Evaporation.