past paper QS Flashcards
(22 cards)
independent variable
is the factor that you purposefully change eg. concentration
dependent variable
responds to the change in the independent variable
control variable
a factor that held constant/controlled
if the reaction between magnesium and
excess hydrochloric acid used an acid with higher concentration
the magnesium would react faster
how does increasing temperature affect rate of reaction
rate increases because particles have more energy so there are more frequent collision
crude oil is formed
by the decomposition of plankton
compare the structure and properties of methane and hexane
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
test for alkene
bromine water:
turns from orange to colourless, its an alkene
copper sulfate test
add water to anhydrous copper
sulfate
colour changes from white
to blue
what is a pure substance
a single element or compound
how distillation is used to obtain potable water from salty water
heat salty water
(so) water evaporates (as water
vapour)
cool the (water) vapour
(which) condenses to form
potable / liquid water
why is obtaining potable water from salty water is more expensive than obtaining potable
water from ground water.
distillation requires energy (to
boil salty water)
(but) ground water only needs
filtering and sterilising
five stages in phytomining
- 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.
disadvantages of phytomining compared with traditional mining methods
(phytomining is) slower to
produce copper
* large area of land required
* insufficient yield to meet
demand
how nitrogen dioxide (NO2) is produced in the engine of a car that burns fossil fuels.
at high temperatures (in the
engine)
nitrogen
reacts with oxygen (to produce
nitrogen dioxide
why carbon dioxide emissions during use and operation are not the total carbon footprint for a car
(because carbon dioxide is
emitted in) extracting /
processing raw materials
(and) manufacturing
(and) disposal at the end of its
useful life
how a sample can be tested to show that carbon dioxide is not present in
the mixture.
use limewater
or
use calcium hydroxide solution
(which) does not turn milky /
cloudy
how a catalyst increases the rate of a reaction.
provides an alternative pathway
(which has) a lower activation
energy
how an equilibrium is reached.
(when) the apparatus prevents
the escape of reactants and
products
(and the) forward and reverse
reactions occur at same rate
how the catalyst affects the equilibrium position.
equilibrium position stays the
same
increases the rate of the forward
and the reverse reaction by the
same amoun
What is the effect of increasing the pressure on the reaction to produce ammonia?
the yield of ammonia increases
The forward reaction is exothermic.
Explain the effect of increasing the temperature on the yield of ammonia gas
produced at equilibrium
yield of ammonia decreases
(because) system shifts in
endothermic direction
