chapter 1: experimental chemistry

Question 1

SI unit of time

Answer 1

second (s)

Question 2

SI unit of temperature

Answer 2

kelvin (K)

Question 3

SI unit of length

Answer 3

metre (m)

Question 4

SI unit of mass

Answer 4

kilogram (kg)

Question 5

SI unit of volume

Answer 5

cubic metre (cm^3)

Question 6

WATER DISPLACEMENT METHOD
- what is the solubility of gas in the water?
- what is the density of gas?
- an example of the gas?

Answer 6

• insoluble to slightly soluble
• density does not affect gas collection
• hydrogen, oxygen, carbon dioxide

Question 7

DOWNWARD DELIVERY
- what is the solubility of gas in the water?
- what is the density of gas?
- an example of the gas?

Answer 7

• can be soluble to insoluble
• denser than air
• chlorine, hydrogen chloride, sulfur dioxide

Question 8

UPWARD DELIVERY
- what is the solubility of gas in the water?
- what is the density of gas?
- an example of the gas?

Answer 8

• can be soluble or insoluble
• less dense than air
• ammonia

Question 9

what is a mixture?

Answer 9

a mixture consists of two or more substances that are not chemically combined

Question 10

what are the different mixtures to separate (eg solid, liquid, gas)?

Answer 10

• solid-solid mixtures
• solid-liquid mixtures
• liquid-liquid mixtures

Question 11

SEPARATING SOLID-SOLID MIXTURES
using magnetic attraction
- how does it work?
- examples of magnetic substances?

Answer 11

• magnetic substances can be separated from non-magnetic substances
• examples are iron, cobalt, nickel and some alloys
  -> waste in a landfill can be sorted using magnetic attraction

Question 12

SEPARATING SOLID-SOLID MIXTURES
sieving
- how is it separated?

Answer 12

a sieve is used to separate solids with different particle sizes

Question 13

SEPARATING SOLID-SOLID MIXTURES
using suitable solvents
- how to separate the solvents?

Answer 13

• solids of different solubility in the solvent can be separated
• solvent: liquid that dissolves in the solvent
• solute: solid that dissolves in the solvent

Question 14

SEPARATING SOLID-LIQUID MIXTURES
filtration
- how does it separate?
- where can it not be dissolved in (insoluble / soluble, solid / liquid)

Answer 14

• separates an insoluble solid from a liquid
• an insoluble solid is one that is unable to dissolve into the liquid it is placed in
  -> filtrate: liquid that passes through the filter
  -> residue: solid that remains on the filter

Question 15

SEPARATING SOLID-LIQUID MIXTURES
evaporation to dryness
- how is it separated?

Answer 15

• separates a dissolved solid from its solvent. the mixture is heated until all the solvent has vaporised

Question 16

SEPARATING SOLID-LIQUID MIXTURES
crystallisation
- how is it separated?

Answer 16

• separates a pure solid from its saturated solution (meaning of saturated solution: in which no more solute can be dissolved)

Question 17

SEPARATING SOLID-LIQUID MIXTURES
simple distillation
- how is it separated?

Answer 17

• separates a pure solvent (liquid) from its solution

Question 18

meaning of miscible liquids

Answer 18

• liquids that form a uniform solution

Question 19

meaning of immiscible liquids

Answer 19

• liquids that do not form a uniform solution

Question 20

SEPARATING LIQUID-LIQUID MIXTURES
chromatography
- how is it separated?

Answer 20

• separates a mixture of substances which have different solubilities in a given solvent
• components in a mixture can be identified by comparing chromatograms of the sample with that of pure substances

Question 21

SEPARATING LIQUID-LIQUID MIXTURES
fractional distillation
- how is it separated?

Answer 21

• separates miscible liquids with different boiling points

Question 22

PURITY OF SUBSTANCES
colourful crystals
- how does a pure crystalline aluminium oxide appear as (appearance, colour)

Answer 22

• it appears as coloured gemstones in the presence of impurities

Question 23

how can the purity of substances be determined?

Answer 23

• a pure substance has a specific melting and / or boiling point under fixed conditions
• mixtures melt or boil over a range of temperatures