1. Experimental Chemistry

Question 1

What are some physical quantities

Answer 1

1. Time is how long takes for something to happen
2. Temperature how hot or cold something is
3. Length is the distance between two points
4. Mass is how much matter is present in a substance
5. Volume is the amount of space something occupies

Question 2

Measurement of time

Answer 2

1. Digital stopwatch: 0.01s
2. Analogue stopwatch: 0.1s

Question 3

Measure of temperature

Answer 3

1. Alcohol thermometer
2. Digital laboratory thermometer
3. Oral digital thermometer

Question 4

Measurement of length

Answer 4

1. 1m=10dm=100cm=1000mm
2. Metre rule
3. Measuring tape

Question 5

Measurement of mass

Answer 5

1. 1kg=1000g=1 000 000 mg
2. Beam balance
3. Electronic balance

Question 6

Measurement of volume

Answer 6

1. 1m³=1000dm³=1 000 000 cm³

Question 7

Different type of measure of volume

Answer 7

Pipette measure accurate fixed volume
3. Volumetric flask measure accurate fixed volumes that are larger
4. Measuring cylinder measures a range of volumes to the nearest 0.5 cm³
5. Burette measures a range of volumes to the nearest 0.05 cm³

Question 8

Measuring the volume of a gas

Answer 8

Using a gas syringe to measure the volume of gas

Question 9

Measuring the volume of a gas

Answer 9

Using a gas syringe to measure the volume of gas

Question 10

How are gases collected?

Answer 10

1. Water displacement when the gas is insoluble
2. Downward delivery where the gas is denser than air
3. Upward delivery where the gas is less dense than air

Question 11

Magnetic attraction

Answer 11

A magnet can be used to separate magnetic solids from non-magnetic solids

Question 12

Sieving

Answer 12

A sieve can be used to separate solids with different particle sizes

Question 13

Using suitable solvents

Answer 13

A suitable solvent can be used to separate solid-solid mixtures in which only one of the solids is soluble in the solvent

Question 14

Filtration

Answer 14

1. Filtration can be used to separate insoluble solids from liquids
2. The liquid that passes through the filter paper is called the filtrate
3. The solid that remains on the filter paper is known as the residue

Question 15

Evaporation to dryness

Answer 15

1. Evaporation to dryness is used to separate a dissolved solid from its solvent by heating the mixture until all the solvent has vaporised
2. The substance with a lower boiling point will turn into a gas first

Question 16

Crystallisation

Answer 16

Crystallisation is used to obtain a pure solid from its saturated solution(is one in which no more solute can be dissolved)

Question 17

Describe the process of crystallisation

Answer 17

1. Gently heat the solution in an evaporating dish to evaporate most of the liquid till the solution is saturated
2. Stop heating the solution before the solvent have evaporated
3. Cool the solution gradually till the crystals appear within the solution
4. Carefully pour the mixture through a funnel lined with filter paper to collect the solid crystals
5. The crystals are washed with some cold distilled water to remove impurities

Question 18

Simple distillation

Answer 18

Simple distillation is used to separate a pure solvent from a solution

Question 19

Describe the process of simple distillation

Answer 19

1. The solution is heated, boiling chips are added for smooth boiling
2. At 100°C , the water boils. The vapour rises and enters the condenser through the exit sidearm of the distillation flask
3. The water vapour cools in the condenser and condense back to liquid water
4. Pure water is collected in the conical flask as the distillate
5. As more water vaporises, the solution becomes more concentrated
6. Eventually, a solid residue of salt remains in the distillation flask

Question 20

Chromatography

Answer 20

Chromatography is used to separate a mixture of substances which have different solubilities in a given solvent

Question 21

Fractional distillation

Answer 21

Fractional distillation is used to separate miscible liquids with different boiling points

Question 22

Describe the process of fractional distillation

Answer 22

1. As the solution is heated, both ethanol and water vapour rise up the column
2. 1 solution has a higher boiling point, it condenses on the cool surfaces within the fractioning column and the solution with higher boiling point returns to the flask
3. The second solution with a lower boiling point continues to rise and exits the column through the sidearm at the top
4. The hot vapour of solution 2 condenses into a liquid as it travels through the inner tube of the condenser
5. Liquid solution 2 flows into the conical flask

Question 23

Purity of substance

Answer 23

A pure substance has a specific melting and/or boiling point under fixed conditions