past paper QS

Question 1

independent variable

Answer 1

is the factor that you purposefully change eg. concentration

Question 2

dependent variable

Answer 2

responds to the change in the independent variable

Question 3

control variable

Answer 3

a factor that held constant/controlled

Question 4

if the reaction between magnesium and
excess hydrochloric acid used an acid with higher concentration

Answer 4

the magnesium would react faster

Question 5

how does increasing temperature affect rate of reaction

Answer 5

rate increases because particles have more energy so there are more frequent collision

Question 6

crude oil is formed

Answer 6

by the decomposition of plankton

Question 7

compare the structure and properties of methane and hexane

Answer 7

methane has 1 carbon atom, hexane has 6
* methane has 4 hydrogen atoms, hexane has 14
* both contain C – H bonds
* only hexane contains C – C bonds
* both are hydrocarbons
* hexane has a higher melting point than methane (or converse)
* hexane has a higher boiling point than methane (or converse)
* methane is a gas at room temperature
* hexane is a liquid at room temperature
* both are small molecules
* hexane has larger molecules than methane
* weak forces between molecules
* forces between hexane molecules stronger than between
methane molecules
* hexane is more viscous than methane
* both are flammable

Question 8

test for alkene

Answer 8

bromine water:
turns from orange to colourless, its an alkene

Question 9

copper sulfate test

Answer 9

add water to anhydrous copper
sulfate
colour changes from white
to blue

Question 10

what is a pure substance

Answer 10

a single element or compound

Question 11

how distillation is used to obtain potable water from salty water

Answer 11

heat salty water
(so) water evaporates (as water
vapour)
cool the (water) vapour
(which) condenses to form
potable / liquid water

Question 12

why is obtaining potable water from salty water is more expensive than obtaining potable
water from ground water.

Answer 12

distillation requires energy (to
boil salty water)
(but) ground water only needs
filtering and sterilising

Question 13

five stages in phytomining

Answer 13

1. Plants absorb metal compounds.
   2.Plants are harvested.
   3.Plants are burned.
   4.Copper compounds from ash are dissolved in acid
   5.Solution of copper compound is electrolysed.

Question 14

disadvantages of phytomining compared with traditional mining methods

Answer 14

(phytomining is) slower to
produce copper
* large area of land required
* insufficient yield to meet
demand

Question 15

how nitrogen dioxide (NO2) is produced in the engine of a car that burns fossil fuels.

Answer 15

at high temperatures (in the
engine)
nitrogen
reacts with oxygen (to produce
nitrogen dioxide

Question 16

why carbon dioxide emissions during use and operation are not the total carbon footprint for a car

Answer 16

(because carbon dioxide is
emitted in) extracting /
processing raw materials
(and) manufacturing
(and) disposal at the end of its
useful life

Question 17

how a sample can be tested to show that carbon dioxide is not present in
the mixture.

Answer 17

use limewater
or
use calcium hydroxide solution
(which) does not turn milky /
cloudy

Question 18

how a catalyst increases the rate of a reaction.

Answer 18

provides an alternative pathway
(which has) a lower activation
energy

Question 19

how an equilibrium is reached.

Answer 19

(when) the apparatus prevents
the escape of reactants and
products
(and the) forward and reverse
reactions occur at same rate

Question 20

how the catalyst affects the equilibrium position.

Answer 20

equilibrium position stays the
same
increases the rate of the forward
and the reverse reaction by the
same amoun

Question 21

What is the effect of increasing the pressure on the reaction to produce ammonia?

Answer 21

the yield of ammonia increases

Question 22

The forward reaction is exothermic.
Explain the effect of increasing the temperature on the yield of ammonia gas
produced at equilibrium

Answer 22

yield of ammonia decreases
(because) system shifts in
endothermic direction