Paper 2 Flashcards
Group 1
2 qualities of Alkali metals
Soft
Low mp/bp
Group 1
As you go down, reactivity…
…increases
Group 1
Reactions with water include:
Lithium = move around surface fizzing Sodium = melts in heat of reaction Potassium = ignites the H2 producued
Group 7
Colour of chlorine
Green poisonous gas
Group 7
Colour of bromine
Red-brown liquid / orange vapour at room temp.
Group 7
Colour of iodine
Dark grey crystalline solid / purple vapour when heated
Group 7
Qualities of halogens
diatomic, mp/bp increases as you go down the group
Group 7
As you go down, reactivity…
…decreases
Test for chlorine
Damp blue litmus paper will be bleached, turning it white
May turn red for a moment as solution of chlorine is acidic
Group 7
What is formed when a halogen and metal react?
A salt called metal halides
Group 7
What is formed when halogens react with hydrogen?
Hydrogen halides, which dissolve in water to form acidic solutions
Group 0
Qualities to noble gases
monatomic, inert, colourless gases, non-flammable
Group 0
Use of argon
Provides inert atmosphere in filament lamps to stop hot filament burning
Group 0
Use of noble gases in flash photography
Argon, krypton and xenon stop flash filament from burning up during high temperatures of flash
Group 0
Uses of helium
Airships / party balloons as it has a lower density than air so can float
Group 0
As you go down the group, bp/mp and density…
…increase
How SA affects rate
The finer the particles of marble chips…
…the faster the reaction, meaning the powered chips on a graph goes up steeper
How conc. affects rate
The more conc. a solution…
… the faster the reaction occurs, so the steeper the line on a graph
How temp. affects rate
The higher the temperature…
…the faster the reaction
Sodium thiosulfate and HCL
What is the experiment?
Use different temperature solutions and time how long it takes for them to react - the reaction is finished when you can’t see a black cross underneath beaker
What does IFOSC
Increased frequency of successful collisions
What are enzymes?
Biological catalysts
How are enzymes used to produce alcoholic drinks?
Enzymes from yeast cells are used in the fermentation process of alcoholic drinks
How do catalysts affect activation energy?
Decrease activity ion energy by providing an alternative reaction pathway that has a lower AE, so more particles have at least the minimum energy to react
Qualities of catalysts
Doesn’t alter products / is unchanged itself / doesn’t use up its mass
Formula for rate of reaction
Amount of reactant used / formed
————————————————
Time
What can be used to measure how much gas is given off?
Gas syringe
What 3 factors impact collision theory?
Temperature / concentration (pressure) / SA
Define an exothermic reaction
One which gives out energy to the surroundings, usually shown by a rise in temp of surroundings
Define an endothermic reaction
One which takes energy in from the surroundings, usually shown by a fall in temp of the surroundings
Graphs of endo- and exo- thermic reactions
Picture 6
Define activation energy
The minimum amount of energy needed for bonds to break and a reaction to start
What is activation energy on a reaction profile
The energy difference between the reactants and the highest point on the curve
Formula for overall energy change
Energy required to break bonds - energy required to make bonds
What reaction is bond breaking?
Endothermic as energy used to break bonds is greater than the energy released by forming them
What reaction is bond making?
Exothermic as the energy released by forming bonds is greater than the energy used to break them
Temperature change
Dissolving salts in water experiment
Adding the salt to a polystyrene cup of water and measuring the change in temp when the salt had dissolved
Dissolving salts in water experiment
Ammonium chloride =
Decreases the temperature of the reaction mixture - its endothermic
Dissolving salts in water experiment
Calcium chloride =
Causes temp of solution to rise = exothermic
Temperature changes
Neutralisation reactions
Most are exothermic
Reaction between ethanoic acid and sodium carbonate is endothermic
Temperature changes
Displacement reactions
Release of energy - exothermic
Temperature changes
Precipitation reactions
Exothermic
What do hydrocarbons contain?
Hydrogen and carbon
Crude oil is:
- a complex mixture of hydrocarbons
- containing molecules in which carbon atoms are in chains or rings
- an important source of useful substances
Is crude oil renewable?
No it’s finite
Qualities of longer hydrocarbons
Higher bp so turn into liquids and drain out of the column early on when they’re near the bottom
Qualities of shorter hydrocarbons
Lower bp so then to liquid and drain out much later on, near to the top of the column where it’s cooler
Use of gases at top of colouring
Domestic heating and cooking
Use of petrol
Used as fuel in cars
Use of kerosene
Used as fuel in aircraft
Use of diesel oil
Fuel in larger vehicles (trains) and some cars
Use of fuel oil
Fuel for large ships and in some power stations
Use of bitumen at bottom of column
To surface roads and roofs
Define a homologous series
A family of molecules which have the same general formula and share similar chemical properties
Neighbouring homologous series differ by:
a CH2 unit
What is viscosity?
The measure of how easily a substance flows
Which fractions have a higher viscosity?
Longer hydrocarbons - thick like treacle
Which fractions have lower viscosity?
Shorter hydrocarbons - runnier
Which hydrocarbons are easy to ignite and why?
Shorter hydrocarbons - have lower bp so tend to be gases at room temp
What state are longer hydrocarbons usually in at room temperature?
Liquid
How do inter molecules forces break in smaller molecules?
Easily as the forces are much stronger in big molecules than in small ones
What is complete combustion?
burning hydrocarbons in plenty of oxygen to produce CO2 and wayer
What sort of reaction is complete combustion?
Exothermic
What is incomplete combustion?
Not enough oxygen is present so the products are:
Carbon dioxide, water, carbon monoxide and carbon (soot)
Why is carbon monoxide dangerous?
Can combine with red blood cells and stop blood from carrying oxygen
A lack of oxygen in blood to brain can lead to fainting, a coma, or death
What is the issues with soot?
Makes buildings look dirty, reduces air quality, can cause or worsen respiratory problems
Where does sulfur dioxide actually come from?
Sulfur impurities in fossil fuels
What happens when sulfur dioxide mixes with clouds?
It forms dilute sulfuric acid, and falls as acid rain
Why is acid rain harmful?
Causes lakes to become acidic so fish and plants die
Kills trees, damages limestone buildings, causes metal to corrode
How are nitrogen oxides formed?
From a reaction between nitrogen and oxygen in the air, caused by the energy released by combustion reactions
Why are nitrogen oxides harmful?
Contribute to acid rain / cause photochemical smog
What is photochemical smog?
A type of air pollution that causes breathing difficulties, headaches and tiredness
Cons to hydrogen as a fuel to power vehicles
Special, expensive engine needed
Expensive to manufacture hydrogen
Hard to store
Not widely availble
Pros to hydrogen as a fuel to power vehicles
Very clean = only water waste product
Renewable
Can be obtained from the water produced by the cell when used in fuel cells
What is cracking
Turning long saturated (alkane) molecules into smaller unsaturated (alkene) and alkane molecules
What happens in cracking
A form of thermal decomposition when one substance breaks down into two new ones when heated
What conditions does cracking need?
Heat, moderate pressure and a catalyst
Why is cracking important?
To meet supply and demand by breaking down unwanted hydrocarbons into wanted ones
What was the earth’s atmosphere in the first billion years?
Volcanoes erupting, releasing gases mainly CO2, steam, methane and ammonia
What gases made up the atmosphere in the first billion years?
Mostly CO2 and water vapour which later condensed to form oceans
What was the Earth’s atmosphere from 1-3 billion years?
A lot of CO2 dissolved into oceans
Green plants evolved over the earth, removing more CO2 and adding O2
How was nitrogen added to the atmosphere 1-3 billion years ago?
N2 gas was formed by ammonia reacting with oxygen, and was also released by denitrifying bacteria
Not reactive so was being made but not broken down
Where did CO2 in the 1-3billion year atmosphere get trapped?
In fossils and sedimentary rocks
What has the presence of oxygen in the last billion years meant for animals?
- early organisms died who couldn’t cope with oxygen in air
- evolution of more complex organisms
What has the presence of O2 in the last billion years made in the atmosphere?
Created the ozone layer O3 blocking harmful rays from the Sun, there is virtually no CO2 left jow
What is the test for oxygen
If the gas is present, it will relight a glowing splint
What is the greenhouse gas effect stages?
- Earth radiates some of the heat radiation it absorbs as longer wavelength = IR
- Some of this IR is absorbed by GG
- Some IR is re-emitted back towards Earth by GG
- Some IR is re-emitted back into space
- The absorption and remission of IR by GG keeps the Earth warm
What is the enchanted greenhouse effect?
Conc of GG increases, more heat radiation from the Earth is absorbed and less is reemitted back into space
How has the increasing human population affected the composition of air?
more people = more land for housing and crops = less trees = less removal of CO2 and production of O2
more energy (fossil fuels) used as well
How has the concentration of methane increased in the atmosphere?
Methane is produced in digestive processes of certain livestock
More livestock to feed growing population means more methane is produced
How can carbon dioxide emissions be reduced?
Limit use of fossil fuels and become more energy efficient
How can data be collected about what the atmosphere was like?
- fossils
- tree rings
- gas bubbles trapped in ice sheets
How do you carry out a flame test?
- clean a nichrome wire loop by dipping it in HCL and rinsing it with distilled water
- dip wire loop in metal compound
- put loop in clear blue part of flame
Flame test for lithium and sodium
Lithium = crimson red Sodium = yellow
Flame test for potassium and calcium
Potassium = lilac Calcium = orange-red
Flame test for copper
Green flame
Metal Ions - Precipitate with NaOH
Colour of aluminium precipitate
White at first, but redissolves in excess NaOH to form a colourless solution
Metal Ions - Precipitate with NaOH
Colour of calcium precipitate
White
Metal Ions - Precipitate with NaOH
Colour of copper precipitate
Blue
Metal Ions - Precipitate with NaOH
Colour of iron(II) precipitate
Green
Metal Ions - Precipitate with NaOH
Colour of iron(III) precipitate
Brown
What is the test for ammonia gas?
Damp red litmus paper will turn blue
Qualities of ammonia
Strong smell, is an irritant and toxic
How do you tell if a substance contains ammonium ions?
Add sodium hydroxide solution to a solution of mystery substance and gently heat it - if ammonia has is given off then it has ammonium ions in it
How do you test for halide ions?
Add some dilute nitric acid followed by a few drops of silver nitrate solution to the halide
Halide Ion Test
Colour of chloride precipitate of silver chloride
White precipitate
Halide Ion Test
Colour of bromide precipitate of silver bromide
Cream precipitate
Halide Ion Test
Colour of iodide precipitate of silver iodide
Yellow precipitate
What is the test for carbonate ions?
Add some dilute acid - if carbonate ions are present, the mixture will fizz as carbonate will react with the acid to produce CO2 gas
What is the test for sulfate ions?
Add dilute HCL to sample - this stops any precipitation reactions not involving the sulfate ions happening
Then add some barium chloride solution - if there are sulfate ions, a white precipitate will form
What is flame photometry?
An instrumental method that allows you to identify ions in a dilute solution
How do you work out which ion is present in flame photometry?
Each ion produces a unique line spectrum with different lines present in different places
How do you work out the concentration of an ion present in flame photometry?
The intensity of the measured wavelength indicates conc.
The intensity can be found using a calibration curve (reading off a graph)
Why is flame photometry better than flame tests?
Can identify different ions in mixtures, but flame tests only identify a single metal ion
Why do chemists often use instrumental analysis (machines) to analyse unknown substances?
Very sensitive - detects tiny amounts
Very fast - automated
Very accurate - no human error
How small are nanoparticles?
1-100nm across, contain a few hundred atoms - so they’re bigger than atoms and simple molecules
What are fullerenes?
Nanoparticles, including nanotubes = tiny hollow carbon tubes - all the carbon bonds make them very string
What is nanoparticles SA:V?
Big SA:V
Why are nanoparticles good catalysts?
Reactions take place on the surface of catalysts, so the big SA gives more space for collisions
How are nanoparticles used cosmetically?
In sunscreens as the small particles provide better protection but don’t leave white marks on the skin
What is the idea behind nanomedicine?
Tiny fullerenes are absorbed more easily by the body than most particles, so they could deliver drugs right into the cells needed
What could lubricant coatings using fullerenes be used in?
Artificial joints and gears
How are nanotubes used in computer chips?
They conduct electricity so can be used in tiny electric circuits
How do nanoparticles improve plastics?
Make them stronger, more durable, without adding much mass
What and why are silver nanoparticles?
Added to polymer fibres used to make surgical masks and wound dressings - gives the fibres antibacterial properties
What are the worries about nanoparticles?
We don’t know the side effects or long-term impacts on health, so they must be tested thoroughly
What is high-density poly(ethene) used for and it’s qualities?
Make water pipes - strong/rigid
What is low-density poly(ethene) used for and it’s qualities?
Plastic bars and squeeze water btls - light/stretchy
What is poly(styrene) used for?
Packing to protect breakable things and as a thermal insulator
What is used to make plastic kettles due to its heat-resistant quality?
Melamine resin and poly(propane)
Qualities of glass
Transparent, strong, can be moulded when hot, brittle when thin
How is glass made?
Soda-lime glass is made by heating limestone, sand and sodium carbonate until they melt - when it cools it is glass
Qualities of clay
Soft when dug up, easy to mould, hardened by high temp, withstands weight
What is clay actually made from?
A mineral formed from weathered and decomposed rock
What are composites?
One material (the reinforcement) embedded in another (the matrix/binder)
Qualities of metals
Good conductors, high density, malleable
Pros to polymers
Flexible, less dense, cheap, insulators
Cons to polymers
Degrade and break down over time so don’t always last long
Pros to ceramics
Insulators, brittle, stiff, strong, hard-wearing, don’t degrade nor corrode
Pros to metals
Conductors, malleable, corrosion resistant metals last a long time
Cons to metal
Corrosion, less brittle so likely to deform but stay in one piece (not shatter)
Cons to composites
Very expensive
Pros to composites
Mix of qualities of two different materials which can be changed for specific pirposes
