GCSE Flashcards
How would you ensure no heat is lost when measuring temperature?
Insulate the funnel to prevent heat loss/temperature drop
Evidence of a chemical reaction:
energy given out
flame produced
precipitate/powder formed
new substance formed
Uses of nanoparticles:
- wound dressings and surgical masks - silver nanoparticles have antibacterial properties and are added to polymer chains
- high SA:V means they can be used as catalyst
- can be used in electrical circuits - some nanoparticles conduct electricity
- in sunscreen
- nanomedicine - fullerenes are absorbed by the body easier so can be used to deliver drugs to cells
Pure substance
contains one element or one compound
Types of bonding:
- covalent - the electrostatic force of attraction between positively charged nuclei and the shared pair of electrons
- ionic - the electrostatic force of attraction between oppositely charged ions
- metallic - the electrostatic force of attraction between positive metal ions and the delocalised electrons
Why does the rate of reaction slow down between hydrochloric acid and marble chips?
acid is used up
so concentration decrease
so fewer collisions per second
so rate decreases
Why does the separator when making industry ethanol contain ethanol + water?
both the water vapour and the ethanol condense
Transition metals vs Alkali metals
Transition metals are:
- denser
- less reactive
- have higher boiling point
- stronger
- conduct heat and electricity
- harder
- form coloured compounds
Ionic compounds properties
- strong bonds - high melting + boiling points
- form lattice structure
- do not conduct when solid but do when molten or in an aqueous solution
Mendeleev left gaps for
undiscovered elements
Why is it important for a company to calculate the mass of product made?
- to know how much product they will make
- so no reactant is wasted
Properties of noble gases:
- inert (unreactive) so non-flammable
- colourless gases
- monatomic gases
- full outer shell (8 electrons)
What is galvanising?
it involves covering iron or alloys of iron (steel) with zinc.
Zinc prevents moisture and air from reacting with the iron causing it to rust.
If the zinc coating gets scratched, the zinc will still corrode instead of the iron as it is more reactive - this is sacrificial protection
How does aluminium not corrode?
aluminium reacts with the oxygen in the air to form a thin layer of aluminium oxide which coats the metal.
If it shows graphite and asks for its element, what is the element?
carbon
Why are alloys stronger than metals?
contain different sized atoms
which disrupts the layers
so layers can’t slide
Alloys are a…
mixture
What are the 2 ways to obtaining a soluble salt from a solution?
- evaporation - heat to evaporate the solvent, crystals will appear, continue to heat until all solvent is evaporated
- crystallisation - heat until crystals just start to form and allow to cool
What reaction conditions can affect the properties of an alkene?
temperature
pressure
catalyst
Conditions needed for iron to rust:
iron + oxygen + water —> hydrated iron(III) oxide
Corrosion only happens at the
surface, where the metal is exposed to air
but the rust/corroded metal flakes off - as it is soft - so a new area is exposed
Corrosion only happens at the
surface, where the metal is exposed to air
but the rust/corroded metal flakes off - as it is soft - so a new area is exposed
Nanoparticles contain how many atoms?
a few 100 - so are therefore 100x larger than atoms
H20 IS NOT H2 so must be a
liquid
A catalyst
provides an alternative pathway with lower activation energy
carbon monoxide is
poisonous
Why is a sun cream with nanoparticles better than one without?
better coverage
protects the skin from harmful UV rays
Impurities will… the melting point and… the melting range
lower, increase
Impurities will… the boiling point
increase
Formulations are used in:
cleaning products
fertilisers
fuels
cosmetics
metal alloys
Test for sulfate ions
add few drops of HCl
add few drops of barium chloride
white precipitate formed if present as barium sulfate formed
Test for halide ions
add few drops of dilute nitric acid
add few drops of silver nitrate
Why should the platinum wire be cleaned before a flame test?
so there are no impurities
Advantages of instrumental methods (like electroscopes) for chemical analysis:
faster
more accurate
require very small amount of sample to measure - more sensitive
The only metal ions that produce a colour other than white in sodium hydroxide are:
copper - blue
iron 2 - green
iron 3 - brown (think rust - which is iron 3 oxide)
aluminium - white to colourless
If no more carbon dioxide gas is produced when calcium carbonate reacts with hydrochloric acid then:
they have stopped reacting
as calcium carbonate has been used up
1 or more chains of polypeptides is a
protein
In a hydrogen fuel cell, the voltage is dependent on:
type of electrodes (want 1 reactive and 1 less reactive for max voltage)
type of electrolyte
temperature of electrolyte
concentration of electrolyte
You can store hydrogen by:
compressing it under high pressures
cooling it
Create a 6V battery with 1.5V cells
connect 4 1.5V cell in series
Non-rechargeable batteries run out because
reaction stops
as reactant is used up
Distilled water is
pure
Carbon/soot can cause… in humans
respiratory problems
Acid rain damages
- buildings and statues
- aquatic animals as it can make lakes acidic - destorying habitats
- trees
Sustainability
Development that meets the needs of current generations without compromising the ability of future generations to meet their own needs
Solar energy is sustainable because
it is renewable
Solar energy may not meet current electricity demands because:
- sunshine is unreliable
- not enough space
- increased demand for energy
Lead is
toxic
Pros of recycling copper
- recycling saves energy
- recycling conserves reserves of copper ore
- recycling reduces waste going to landfill sites
- mining/quarrying damages habitats
How is glass recycled?
separated by colour and chemical composition
crushed
melted
and reshaped into new glass objects
Bioleaching
bacteria convert copper compounds to soluble copper compounds - which separate the copper from the ore
the leachate contains copper ions and can be extracted through electrolysis or displacement with scrap iron
Leachate
solution produced by bioleaching
Phytomining
grow plants in soil containing copper ions
copper builds up on leaves - can’t be used by plants
the plant is harvested, dried and burnt
ash produced contains copper ions and is dissolved into acid
solution is electrolysed
Why is phytomining not used often?
takes a long time - slow
land not available
high grade ores still available
Methods of desalinating salty water - with loads of energy
distillation
reverse osmosis
Potable water
water taken from rivers or aquifiers
it is screened
pass through wire mesh to remove large solid bits - e.g. twigs
pass through bed of sand + gravel - to remove undissolved solids
sterilise it using ozone, chlorine gas or UV rays
to kill microbes
Obtaining fresh water from wastewater is more difficult because:
it requires more processes
as it contains more microbes and more toxic chemicals
Why is producing drinking water from salt water expensive?
it requires lots of energy
Alloys are… than pure metal
harder
A stronger acid has a … ph which means it has a … concentration of …
very low
higher concentration
H+ ions
If the reaction is reversible, then the acid is … + why?
weak
as partial ionisation
Why does a strong acid have a faster rate of reaction?
higher concentration of H+ ions
so more collisions per second
Write an ionic equation for the neutralisation of hydrochloric acid with
potassium hydroxide.
H+ + OH- —> H2O
Why is a metal oxide or carbonate added to an acid until it is in excess?
to make sure all the acid reacts
