1.3 how are substances in mixtures seperated + 1.4 how can the purity of a substance be determined

Question 1

types of mixtures

Answer 1

1. solid-solid mixtures
   2.solid-liquid mixtures
   3.liquid- liquid mixtures

Question 2

separating techniques for solid-solid mixtures

Answer 2

magnetic attraction
sieving
using suitable solvents
sublimation

Question 3

magnetic attraction

Answer 3

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

Question 4

sieving

Answer 4

a sieve can he used to separate solids with different particle sizes

Question 5

when is sieving used

Answer 5

when a mixture consists of bigger and smaller particles, they can be separated by using a sieve with suitable pore sizes

Question 6

using suitable solvents

Answer 6

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

Question 7

solvents

Answer 7

liquids that can dissolve solids

Question 8

solutes

Answer 8

solids that dissolve in solvent

Question 9

sublimation

Answer 9

can be used to separate a substance that changes from the solid to the gaseous state directly

Question 10

how does sublimation work

Answer 10

the solid sublimes into a gas and moves away from the mixture
the gas will change state back to a solid on the cool surface (eg. boiling tube filled with ice)
results in a solid deposit known as sublimate

Question 11

how can sublimate be collected

Answer 11

by scraping them of the cool surface

Question 12

separating techniques for solid-liquid mixtures

Answer 12

filtration
evaporation to dryness
crystallisatiom
simple distillation

Question 13

filtration

Answer 13

used to separate insoluble solids from liquids

Question 14

filtrate

Answer 14

liquid that passes through filter paper

Question 15

residue

Answer 15

solid that remains on filter paper

Question 16

evaporation to dryness

Answer 16

used to separate dissolved solid form its solvent by hearing the mixture until all the solvent has vaporised

Question 17

crystallisation

Answer 17

used to obtain a pure solid form it’s saturated solution

Question 18

saturated solution

Answer 18

a solution in which no more solute can be dissolved

Question 19

when is crystallisation used

Answer 19

when a solute decomposes or breaks down into simpler substances when strongly heated

Question 20

simple distillation

Answer 20

send to separate a pure solvent (liquid) from a solution

Question 21

parts of a simple distillation set up

Answer 21

thermometer
distillation flask
bunsen burner
condenser
round bottom flask
flask (to collect distillate)

Question 22

process of distillation (for salt water)

Answer 22

1.solution is heated. At 100 °C, the water boils. the vapour rises and enters the condenser through the exit sidearm of the distillation flask
2. water vapour cools in the condenser and condenses back to liquid water. pure water is collected in the conical flask as the distillate.
3.as more water vapour ones, the salt solution becomes more concentrated. eventually, a solid residue of salt remains in the distillation flask.

Question 23

separating techniques for liquid liquid mixtures

Answer 23

separating funnel
chromatography
fractional distillation

Question 24

miscible liquids

Answer 24

liquids that form a uniform (homogeneous) solution when mixed together

Question 25

immiscible liquids

Answer 25

liquids that do not mix well together (heterogenous) forms layers know as phases when left undisturbed (least dense at the top and densest at the bottom)

Question 26

separating funnel

Answer 26

used to separate immiscible liquids (liquids that form not mix well with each other

Question 27

how does a separating funnel work

Answer 27

a heterogeneous mixture is left to settle and separated into layers each component can be removed by opening the tap at the bootleg and collecting it in separate flasks or beakers

Question 28

chromatography

Answer 28

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

Question 29

chromatograms

Answer 29

show the separated substances on the paper after chromatography

Question 30

retention factor

Answer 30

distance a particular substance moves compared to solvent front

Question 31

retention factor (rf) value formula

Answer 31

distance travelled by substance/ distance travelled by the solvent

Question 32

locating agents

Answer 32

chemicals that react with colourless substances to form coloured spots

Question 33

application of chromatography

Answer 33

-identity unauthorised substances (eg pesticides and poisons in food) -detect small quantities of banned substances in an athlete urine or blood sample -separate components like DNA fragments in samples for forensic investigations

Question 34

fractional distillation

Answer 34

used to separate miscible liquids with different boiling points

Question 35

how does fractional distillation work (ethanol water mixture)

Answer 35

1.as the solution is heated , both ethanol and water vapour rises up the column 2.water has a higher boiling point than ethanol. the water vapour condenses on the cool surfaces within the fractionating column and the liquid water returns to the flask 3.ethanol vapour condenses to rise. at its boiling point 78 °C, it exits the column through the sidearms at the top 4.hot ethanol vapour cools and condenses into a liquid as it travels through the inner tube of condenser 5.liquid ethanol (distillate) flows into conical flask (receiver)

Question 36

part of fractional distillation set up

Answer 36

thermometer condenser fractionating column glass beads/ plates found in fractionating column round bottom flask bunsen burner receiver (for distillate)

Question 37

purity or a substance

Answer 37

a pair substance has a specific melting and or boiling point t under fixed conditions