chapter 4

Question 1

types of separation techniques

Answer 1

• magnetic attraction
• filtration
• distillation
• chromatography

Question 2

separating a mixture of magnetic and non-magnetic substances

Answer 2

magnetic attraction

Question 3

how does magnetic attraction work

Answer 3

magnetic substance will be attracted to the magnet, which would be placed near the substances

Question 4

application of magnetic attraction

Answer 4

scrapyards: iron attracted in scrapyards can be reused/recycled

Question 5

separating a mixture of substances with different particle sizes/ soluble substance mixed with insoluble substance

Answer 5

filtration

Question 6

filter paper characteristic

Answer 6

has pores of different sizes:
particles bigger than the pores will be retained as residue, particles smaller than the pores will be collected as filtrate

Question 7

filtration technique example

Answer 7

a mixture of chalk and water is pored on a filter

Question 7

components of filtration technique

Answer 7

• filter funnel lined with filter paper
• container for the filtrate

Question 8

filtering process example

Answer 8

• a mixture of chalk and water is poured into a filter funnel lined with filter paper, which acts as a sieve
• the pores of the filter paper allow water particles to pass through, but not chalk particles, which are bigger than the pores -> retained by the filter paper
• solid that is left on the filter paper: residue
• liquid that passes thorugh the filter paper: filtrate

Question 9

application of filtration (tea)

Answer 9

a tea strainer that seperates tea leaves from the tea
- tea leaves remain in a tea strainer while the tea passes through the holes in the tea strainer

Question 10

application of filtration (nose)

Answer 10

the hair the nostrils + mucus (thick liquid produced in the nose), help trap large solid particles in the air that we breather in
- prevents such particles from entering the lungs

Question 11

obtaining a solute from a solution

Answer 11

evaporation

Question 12

evaporation explained

Answer 12

the solvent changes from liquid to gas state at a much lower temperature than the solute. after the solvent evaporates, we will be left with the solute as residue

Question 13

components of evaporation

Answer 13

• evaporating dish/ crucible
• wire gauze
• tripod stand
• bunsen burner

Question 14

evaporation process example

Answer 14

• heat is applied to the salt solution in the crucible, speeding up the change of water into water vapour
• water changes state at a lower temperature than salt, thus evaporating and leaving salt as the residue

Question 15

applications of evaporation

Answer 15

preserving food:
- as water is essential for the decomposition of food, removing water through evaporation allows the preservation of herbs, spices, dried small fishes (ikan billies) etc…

Question 16

obtaining liquid from a mixture of substances with different boiling points

Answer 16

distillation

Question 17

distillation explained

Answer 17

a mixture is boiled, and the substance with the lowest boiling will gain heat and evaporate to form vapour. the vapour will come in contact with the cooler surfaces in the condenser, lose heat contract and condense to become condensed vapour, which is collected.

Question 18

components of distillation

Answer 18

• distillation flask
• boiling chips (smooth boiling)
• thermometer (mouth of the condenser)
• condenser
• receiving flask
• bunsen burner

Question 19

distillation process explained

Answer 19

• salt solution is heated in the distillation flask until it starts to boil
• water gains heat and changes into steam which passes thorugh the condenser
• the condenser, with cold water running thorugh it, acts as a cold surface that the vapour loses heat to, and condenses into pure water (distillate)

Question 20

distillation application (pure water)

Answer 20

obtaining pure water using a solar still
- two rocks clamp down a plastic sheet, in which a pebble is place on top of in the middle
- water form the ground start to gain heat and evaporate to form water vapour, which loses heat to the cool plastic sheet, and condenses to form pure water droplets, which drop downwards and into the cup due to the rock on top.

Question 21

distillation application (perfume)

Answer 21

obtaining perfume:
- plant parts (eg: petals) are boiled in water
- vapour collected as the distillate is made into perfumes

Question 22

separating a mixture of substances that dissolve to different extents in a solvent

Answer 22

chromatography

Question 23

chromatography explained

Answer 23

• some substances are more soluble than others, which will travel longer distances form the starting point
• insoluble substances will remaind at the starting point

Question 24

chromatography components:

Answer 24

• filter paper
• ink spot on paper
• on the drawing line (pencil drawn)
• water

Question 25

chromatography process

Answer 25

• a drop of ink is placed near the bottom of the filter paper
• the paper strip is dipped into water (commonly the solvent)
• water travels up the filter paper with the substances in the ink
• substance X, the most soluble, travels the furthest distance
• substance Y, insoluble, remains at the starting point

Question 26

application of chromatographys

Answer 26

• identify colours in dyes
• identify substance used in food products

Question 27

sources of water in singapore

Answer 27

• imported water
• local catchment
• NEWater
• desalinated water

Question 28

desalination of water

Answer 28

• pre-treated seawater is pumped through partially permeable membranes at high pressure
• membrane: thin piece of material with small pores
• allows water particles, but not salt particles, to pass through

Question 29

conserve water

Answer 29

3Rs:
- reduce
- reuse
- recycle