Chemistry Flashcards
What do states of matter depend on?
The forces between particles
Describe the shape and volume of a solid
Definite shape and volume
Describe the arrangement of a solid
Fixed regular lattice arrangement
Describe the amount of energy in a solid
Low
Describe the movement of a solid
Vibrate around a fixed point
Describe the shape and volume of a liquid
Undefinite shape but definite volume
Describe the arrangement of a liquid
Random arrangement
Describe the amount of energy in a liquid
More energy than solid, but less than liquid
Describe the movement of a liquid
Random motion, sliding past each particles
Why do liquids expand when heated?
As they get hotter, they move more
Describe the shape and volume of a gas
Undefinite shape and volume
Describe the arrangement of a gas
Random
Describe the amount of energy in a gas
High
Describe the movement of a gas
Random and fast
What happens to gases when they get hotter?
They either expand or increase in pressure
What is a physical change?
A substance changing state
When do chemical changes occur?
During chemical reactions
What actually happens in a chemical reaction?
Atoms are rearranged
What type of change is harder to reverse?
A chemical change
What does it mean if a substance is pure?
It’s completely made up of a single elements or compound
What does it mean if a substance is a mixture?
It contains more than one compound/element
What is the different in melting/boiling points between pure and impure substances?
Pure substances have a specific, sharp melting/boiling point
Impure substances don’t have a specific, sharp melting/boiling point
What does simple distillation separate?
The liquid from a solution
What goes through the condenser?
Cold water
Roughly, describe the diagram for distillation
Flask with solution and thermometer, connected to a condenser which then connects to a beaker to collect the distillate
If a liquid is flammable how do you heat it?
Water bath or electric heater
Why is simple distillation not as good as fractional?
Simple can only be used to separate solutions with very different boiling points
In fractional distillation, what do you attach to the flask?
Fractionating column and a condenser
What do you put in the fractionating column?
Glass rods
Why do you put glass rods in the fractionating column?
To provide large surface area for hot vapours to cool and condense repeatedly.
In fractional distillation once the first liquid has been collected, what do you do next?
Raise the temperature to the next liquids’ boiling point
Which order of boiling points do you go, when undergoing fractional distillation?
Lowest point to highest point
What is filtration used to separate?
An insoluble solid from a liquid
Describe the apparatus for filtration
Filter paper, in the shape of a cone, into a funnel
What is left behind when filtrating?
Solid residue
What is crystallization used to separate?
A soluble solid from a solution
Roughly, give steps to the method of crystallization
Pour solution into evaporating dish and heat, making the solution more concentrated
Remove dish and leave to cool
Salt should start to form crystals, then filter crystals and leave in warm place to dry
Why do crystals start to form during crystallization?
Because the salt becomes insoluble in the cold, highly concentrated solution
What is chromatography used to separate?
A mixture of soluble substances
In chromatography, what is the mobile phase?
The phase where the molecules can move
What state are the molecules in during the mobile phase?
Liquid or gas
In chromatography, what is the stationary phase?
The phase where the molecules can’t move
What state are the molecules in during the stationary phase?
Solid or a really thick liquid
Why do the substances spend different amounts of time in each phase?
Because they spend different amounts of time dissolved
How fast a chemical moves depends on what?
How it distributes itself
What is the baseline, in chromatography?
The line drawn near the bottom of the paper
Why do you draw the baseline with a pencil, in chromatography?
The pencil mark is insoluble therefore it won’t move up the paper
How far do you dip the paper in, in chromatography?
Just before the spot
What do you put on top of the beaker, in chromatography?
A watch glass
As the solvent moves up the paper, what else moves with it?
The chemicals
What do you do once all chemicals have stopped dissolving in chromatography?
Remove the paper and measure the distance the solvent has moved
The amount of time spent in each phase, in chromatography, depends on what?
How soluble the solvent is
How attracted they are to the stationary phase
What phase will, chemicals with a high solublity, spend the most time in?
Mobile so they’ll be carried further up the paper
What is the name of the piece of paper left after chromatography?
A chromatogram
What is the equation for Rf value?
Distance travelled by solute / Distance travelled by solvent = Rf
What are the units for Rf?
There aren’t any as Rf is a ratio, and ratios don’t have units
Why can you use chromatography to measure the purity of substance
If a substance is pure it won’t be separated and will remain as one blob
Therefore, if the solution remains together it is pure
What are the three types of water resources in the uk?
Surface, ground and waste water
Give examples of surface water
Lakes, rivers and reservoirs
Give an example of ground water
An aquifer (rocks that trap water underground)
What types of water resources require purification?
Surface and waste water
Name the three steps in water treatment plants?
Filtration, sedimentation and chlorination
What occurs in the filtration stage in water treatment plants?
A wire mesh screens out large object
Gravel or sand beds filter out any other solid bits
What occurs in the sedimentation stage in water treatment plants?
Iron or aluminium sulfate is added to the water which makes fine particles clump together and settle at the bottom
What occurs in the chlorination stage in water treatment plants?
Chlorine gas is bubbled through to kill harmful bacteria and other microbes
What are some examples of disadvantages of distilling sea water?
Loads of energy needed and very expensive
What type of water mused be used in chemical analysis?
Pure (deionised) water
Why is deionised water used in chemical reactions?
Deionised water contains no ions, if it did contain ions, even the smallest amount could give your experiment a false result
What is our main source of hydrocarbons?
Crude oil
How is crude oil formed?
High temperature and pressure over millions of years
What is a hydrocarbon?
A compound containing only hydrogen and carbon
State two types of hydrocarbons
Alkanes and alkenes
How can crude oil be separated?
By fractional distillation
Roughly describe how crude oil can be separated
The crude oil is boiled into a gas
Gas then enters fractionating column which has a temperature gradient which then seperates the hydrocarbons based off their boiling points
How does the length of the hydrocarbon change the boiling point?
As the length of the hydrocarbon increases, the boiling point also increases as there are more bonds to break
Where do the short hydrocarbons come out the fractionating column?
The top
Where do the long hydrocarbons come out the fractionating column?
The bottom
List the hydrocarbons that come out at each fraction
Gases, Petrol, Kerosene, Disel Oil, Fuel Oil and Bitumen
What are gases used for?
Heating and cooking
What is petrol used for?
Fuel for cars
What is kerosene used for?
Fuel for aircrafts
What is disel oil used for?
Fuel for some cars and large vehicles
What is fuel oil used for?
Fuel for large ships and power stations
What is bitumen used for?
To surface roads and roofs
What is a homologous series?
A family of molecules which share the same general formula and chemical properties
Name an example of a homologous series
The alkanes
Name some alkanes
Methane, Ethane and Propane
What determines a hydrocarbons properties?
It’s size
What does the size of a hydrocarbon decide?
What fraction it will separate to and it’s viscosity
What is viscosity a measure of?
How easily a substance flows
True or False? The longer the hydrocarbon, the higher the viscosity
True
Why do hydrocarbons make great fuels?
They release lots of energy when burnt with oxygen (very exothermic)
What is the equation of complete combustion of a hydrocarbon?
Hydrocarbon + Oxygen -> Carbon Dioxide + Water
When does incomplete combustion occur?
When a hydrocarbon burns in a limited supply of oxygen
What is the main difference between the products of complete and incomplete combustion?
Incomplete combustion contains less oxygen than carbon dioxide
What is the equation of incomplete combustion of a hydrocarbon?
Hydrocarbon + Oxygen -> Carbon Monoxide + Carbon (Soot) + Water
Why is carbon monoxide bad?
Because it can combine with red blood cells and prevent your blood from carry oxygen
A lack of oxygen can lead to fainting, coma or even death
Why is soot bad?
It makes buildings look dirty, reduces air quality and can cause or worsen respiratory problems
What does sulfur dioxide cause?
Acid rain
What else is released when fossil fuels are burned?
Sulfur dioxide and various other nitrogen oxides
How does sulfur dioxide become acid rain?
The gas mixes with the clouds and forms dilute sulfuric acid which then falls as acid rain
What are some disadvantages of acid rain?
Makes lakes acidic - kills animals and fishes
Kills trees, damages limestone buildings/statues and can corrode metal
What reaction creates nitrogen oxide?
A reaction between nitrogen and oxygen
What causes the energy needed to cause nitrogen to react with oxygen?
Combustion reactions
Give an example of a combustion reaction which causes nitrogen to react with oxygen?
Internal combustion engines of cars
What can nitrogen oxides contribute to?
Acid rain or, at ground level, can cause photochemical smog
What can photochemical smog cause?
Breathing difficullties, headaches and tiredness
What are the pros of using hydrogen in cars?
Very clean
Only waste product is water
Renewable resource
Chain reaction as hydrogen can be obtained from waste product (water)
What are the cons of using hydrogen in cars?
Special and expensive engine needed
Hydrogen needs to be manufactured which is expensive and requires energy from another source
Hydrogen is hard to store and, at the moment, is not widely used
What is cracking?
The splitting up of long-chain hydrocarbons?
What does cracking use and create?
Long saturated alkane molecules into smaller unsaturated alkene and some alkane molecules
What is the most useful product of cracking?
The alkane molecules
What is cracking a form of?
Thermal decomposition
What is thermal decomposition?
When one substance breaks down into at least two new ones when you heat it
Why is alot of energy needed in cracking?
Strong covalent bonds needed to be broken
What is often added to cracking as alot of energy is needed?
A catalyst
What does cracking usually involve?
Heat, moderate pressure and a catalyst
Name an example of a catalyst used in cracking?
Aluminium Oxide
What does cracking help?
Match supply and demand
What was the first phase of the atmosphere?
Volcanoes gave out steam and carbon dioxide
What did volcanoes release?
Carbon dioxide, steam, methane and ammonia
When things settled down, what was the early atmosphere mostly?
Carbon dioxide and water vapour
What later happened to the water vapour in the atmosphere?
It condensed to form the oceans
What was the second phase of the atmosphere?
Green plants evolved and produced oxygen
What happened to the carbon dioxide in the atmosphere?
It dissolved into the ocean
How was nitrogen then put into the atmosphere?
Denitrifying bacteria and by ammonia reacting with oxygen
Why didn’t the amount of nitrogen in the atmosphere decrease?
Because it’s very unreactive so although it’s being made it’s not being broken down
How did oxygen then be produced?
Green plants evolved to photosynthesise
Due to plants evolving, what happened to the air concentration?
Oxygen increased whilst carbon dioxide decresed
What did carbon dioxide eventually get locked up in?
Fossil fuels and sedimentary rocks
What was the third phase of the atmosphere?
Ozone layer allowed the evolution of complex animals
What did the build up of oxygen in the atmosphere kill of?
Early organisms that couldn’t tolerate the high amounts
What did the excess oxygen also create?
The ozone layer
What did the ozone layer do?
Block out the harmful rays from the sun and enables the more complex organisms to evolve
What is the test for oxygen?
A glowing splint relighting
Why and what does more people mean in terms of energy?
More energy is needed as more lighting, cooking, transport and heating needed
Why does an increasing population affect carbon dioxide concentration
More people, more houses needed, more land needed so more trees cut down therefore less carbon dioxide absorbed
What effect helps to keep the Earth Warm?
The Greenhouse Effect
What does the Sun give out?
Electromagnetic radiation
What does the Earth radiate?
The heat radiation it asorbs
What happens to the heat radiation?
Either absorbed or re-emitted back towards Earth by the greenhouse gases, re-emitted into space
Define greenhouse gases
The gases in the atmosphere that can absorb and reflect heat radiation
Give examples of greenhouse gases
Carbon dioxide, water vapour and methane
What happens to the greenhouse effect if concentration of greenhouse gases are increased?
More enchanced greenhouse effect
Give an example on how methane is produced
Through digestive processes of certain livestock
Why is methane so worrying even though its in tiny amounts?
It’s a super effective greenhouse gas
Define anthropogenic
Caused by humans
Why is historical data less accurate?
Less records and data collected was less accurate (not as good apparatus)
What are methods of estimating past data?
Fossils, tree rings or gas bubbles
True or False? Alkanes are saturated hydrocarbons?
True, they have used all their bonds
What is the general formula for alkanes?
CnH2n+2
What type of bond occurs in an alkene?
A double carbon to carbon bond
What is a functional group?
A group of atoms that determine how a molecule reacts
True or False? Members of a homologous series all contain different functional groups?
False, the function group controls the properties of the molecule and all molecules in a homologous series all have the same properties
What is the functional group in alkenes?
The double carbon to carbon bond
What is the general formula for alkenes?
CnH2n
Are alkenes saturated or unsaturated? Why?
Unsaturated, they can make more bonds as the double bond can open up allowing the two carbon atoms to bond with other atoms
What is the test for an alkene?
When shaken together, bromine water will decolourise (orange to colourless)
Why can you use bromine water to test for an alkene?
Because the bromine is added across the alkene double bond
What happens to the hydrocarbons in the combustion reactions?
Oxidised
What is the functional group in alcohols?
-OH
What is the general formula for alcohols?
CnH2n+1OH
Why don’t you write CH40 instead of CH3OH?
CH40 doesn’t show the -OH functional group
What is a dehydration reaction?
When alcohol and an acid catalyst is heat it will form an alkene and water
What can alcohols be oxidised to form?
Carboxylic acid
What are the properties of carboxylic acids?
React like other acids
Partially ionise and release H+ ions (weak acid)
What is the general formula for a carboxylic acid?
CnH2n-1COOH
What is the functional group is carboxylic acid?
-COOH
How do you form a carboxylic acid?
By oxidising an alcohol
What is the process by which ethanol is made?
Fermentation
What “ingredients” does fermentation involve?
Sugar and yeast
What is the formula for fermentation?
C6H1206 -> 2C2H50H + 2CO2
What do yeast cells contain that helps the process of fermentation?
Enzymes
Roughly, describe the process of fermentation
Mix yeast and glucose in container and leave in warm place
Keep between 30-40*C and in anaerobic conditions
What causes the yeast cells in fermentation to die?
The high concentration of acid (usually 20%)
How do you collect the ethanol?
From the top as the yeast cells would of died and sunk to the bottom
What temperature should fermentation take place at?
30-40*C
What type of conditions should fermentation take place at?
Anaerobic
What is used to concentrate ethanol?
Fractional Distillation
Compare the boiling points of ethanol and water
Ethanol has a lower boiling point
What is the name of the condenser used to condense the ethanol vapour?
Liebig condenser
True or False? Alcohol can’t be used as a fuel?
False
Why can alcohol be used as a fuel?
When burned, they release energy
When investigating which alcohol is the best fuel, what do you use for heat?
A spirit burner
When investigating which alcohol is the best fuel, what is the independent variable?
The Alcohol
When investigating which alcohol is the best fuel, what is the dependent variable?
The Mass of the Alcohol after burning
How much water is usually used when investigating which alcohol is the best fuel?
100cm3 distilled water
What contained is used when investigating which alcohol is the best fuel?
Copper calorimeter
When investigating which alcohol is the best fuel, how do you insulate the calorimeter?
By using a draught excluder and an insulating lid
When investigating which alcohol is the best fuel, how do you measure the temperature?
Using a thermometer
Why is the calorimeter insulated when investigating which alcohol is the best fuel?
To get the most accurate results
When investigating which alcohol is the best fuel, why should you avoid the flame and alcohol touching?
Alcohol is extremely flammable therefore direct contact could lead to danger
When investigating which alcohol is the best fuel, how much temperature do you need to let the water rise to?
By 20*C
Once wick blown out, what do you do?
Rewigh the burner and fuel
What makes an alcohol more efficient when investigating which alcohol is the best fuel?
The less fuel lost, the more efficient the fuel
How does the length of the hydrocarbon relate to its efficiency as a fuel?
The longer the chain, the more efficient the fuel will be
What are polymers?
Substances of high average relative molecular mass by joining up lots of small repeating units called monomers
What type of bond can be found between monomers that make up addition polymers?
Double covalent bonds
What is addition polymerisation?
Lots of unsaturated monomer molecules (eg aklenes) opening up their double bonds to join together to form polymer chains
What type of molecules can undergo addition polymerisation?
Unsaturated monomer molecules
True or False? When drawing polymers/monomers, you surround both with brackets?
False, only polymers are surrounded in brackets, this is to show the molecule is repeated
Name examples of synthetic polymers
poly(tetrafluoroethene) (PTFE), poly(chloroethene) (PVC), poly(ethene) and poly(propene)
What are poly(ethene)’s properties?
Flexible, insulator and cheap
What are poly(ethene)’s uses?
Plastic (bags and bottles) and wire insulators
What are poly(propene)’s properties?
Flexible, strong, tough and moudable
What are poly(propene)’s uses?
Crates, furniture and ropes
What are poly(chloroethene)’s properties?
Tough and cheap
What are poly(chloroethene)’s uses?
Window frames and water pipes
What are poly(tetrafluoroethene)’s properties?
Unreactive, tough and non-stick
What are poly(tetrafluoroethene)’s uses?
Non-stick pans and waterproof clothing
How can polymers be made?
Addition polymerisation or condensation polymerisation
What is condensation polymerisation?
Two different types of monomer react and form bonds between them making polymer chains
How many functional groups must a condenation polymer have?
Atleast two
What is lost when a new bond form between twi different monomers?
A small molecule (eg water)
What are examples of condensation polymers?
Polyesters
What two monomers react to form a polyester?
Dicarboxylic acid and diol
Dicarboxylic acid monomers contain what function group?
Two carboxylic acid groups (-COOH)
Diol monomers contain what function group?
Two alcohol groups (-OH)
What link is formed when a carboxylic acid reacts with an alcohol?
An ester link
Why is a polyester an example of a condensation polymer?
Each time an ester link is formed, a molecule of water is lost
Name examples of naturally occuring polymers
DNA, proteins and starch/cellulose
Name examples of naturally occuring monomers
Nucleotids, amino acids, carbohydrates
What is DNA?
A complex molecule that contains genetic infomation
What is DNA made up of?
Four different monomers called nucleotides, in two strands
What is an example of protein usage in the human body?
Enzyme development
What are proteins made up of?
Amino acids
How do amino acids form proteins?
Condensation polymerisation
What are carbohydrates?
Molecules containing carbon, oxygen and hydrogen
What are carbohydrates used by?
Living things (to produce energy)
What are plastics made from?
Crude oil
Why is using up crude oil bad for crude oil suppliers?
Cost to supply will increase
Why is using up crude oil bad for customers?
Cost of crude oil products will increase
Disadvantages of using land fill for disposal of polymers?
Valuable land wasted
Most polymers are non-biodegradable so will stay there for years and years
Disadvantages of using combustion for disposal of polymers?
If not controlled, toxic gases can be released, for example when PVC is burnt it produces HCL
Carbon dioxide is produced, which contributes to global warming
Recycling polymers advantages?
Reduces the amount of non-biodegradable waste in landfill sites
Reduces emissions of green house and toxic gases
Recycling generally saves money and creates jobs
Uses less water and energy
Recycling polymers disadvantages?
If mixed together, quality of final product could be reduced
Polymers must be seperated by type before recycled
Polymers can only be recycled a finite number of times as the strength of the polymer can decrease
Melting down polymers can release dangerous gases into the atmosphere
When/what did/how John Dalton describe atoms?
The start of the 19th century, atoms as solids that are made up of different elements
When/what did/how J J Thomson describe atoms?
1897 and he concluded that atoms weren’t solid spheres and that there must be even smaller negatively charged particles
What was the name of the theory J J Thomson created about atoms?
The Plum Pudding Model
How was the plum pudding model disproved?
Alpha particles were fired at an extremely thin sheet of gold
Expected all to transmit through
Some did transmit through but some reflected
Who came up with the nuclear atom theorem?
Rutherford
What is the charge of a proton?
+1
What is the relative atomic mass of a proton?
1
What is the charge of a neutron?
0
What is the relative atomic mass of a neutron?
1
What is the charge of a electron?
-1
What is the relative atomic mass of a electron?
0.0005
Why does a nucleus have a positive charge?
Because it has more protons (n) than electrons (0)
What does the atomic number tell you about an element?
The number of protons within the nucleus
What does the mass number tell you about an element?
The number of proteins added to the number of neutrons (Relative atomic mass of nucleus)
What is an isotope?
A different form of the same element which have the same number of protons but different number of neutrons
What is relative atomic mass?
The average mass of one atom of an element, compared to mass of 1/12 of carbon-12
How do you calculate the relative atomic mass of an element?
Multiply each relative isotopic mass by its abundance then add up the results
Then divide the sum by the total isoptopic abundance
How did Mendeleev originally order his table of elements?
Based off properties of the elements and their compounds
What caused Mendeleev to change the table of elements order to atomic mass?
He noticed a pattern if he put similar chemical properties in columns
What caused Mendeleev to make mistakes in the table of elements?
He didn’t realise he was looking at the isotopes of that element
What discovery caused the order of the periodic table to change to atomic number?
The discovery of protons and electrons
What on the periodic table shows elements with similar chemical properties?
Groups (columns)
What on the periodic table shows elements with the same outer shell number?
Periods (rows)
What on the periodic table shows elements with the same number of electrons in the outer shell?
Groups (columns)
What are ions?
Charged particles
True or False? Ions can be single atoms and groups of atoms?
True, for example Na+ or N03-
Why do atoms ionise?
To gain a full outer shell (stable electronic structure)
What are negative ions called?
Anions
What are positive ions called?
Cations
Compare the number of electrons and protons in a cation
More protons than electrons
Compare the number of electrons and protons in anion
More electrons than protons
What is the overall charge of an ionic compound?
Zero
What attracts the cation and anion in ionic bonding?
Electrostatic forces
What is ionic bonding between?
A metal and non-metal
Describe the structure of an ionic compound
Giant ionic lattice
Describe the forces of attraction in an ionic compound
Very strong electrostatic forces of attraction
What are the properties of an ionic compound?
High melting/boiling point
Dissolve easily
Unconductive, unless in solution (aqueous) or melted (liquid)
What do ionic compounds have a high melting/boiling point?
A large amount of energy needed to break the very strong electrostatic forces of attraction
What do ionic compounds dissolve easily?
Ion’s will seperate easily and begin free to move in a solution
What don’t ionic compounds conduct?
Fixed in place and can’t move therefore must be aqueous or liquid because ions are free to move
What are the advantages of 2D representations?
- Great at showing what is actually in the molecule
- Great at showing how much is actually in the molecule
- Great at showing what type of bonds are present
What are the disadvantages of 2D representations?
- Can’t see the size of the atom/molecule
- Can’t see the shape of the molecule
What are the advantages of dot and cross diagrams?
- Great at showing where the electrons came from
- Great at showing what bonds are present
What are the disadvantages of dot and cross diagrams?
- Can’t see the size of the molecule
- Can’t see how the molecules arranged
What are the advantages of 3D representations?
- Great at showing the arrangement of molecules
- Great at showing the size of the molecules
- Great at showing the shape of the molecules
What are the disadvantages of 3D representations?
- Can’t see the inner layers (can only see the outer layers)
What are the advantages of ball-stick models?
- Great at helping to visualise structures
- Good as being more realistic than 2D drawings
What are the disadvantages of ball-stick models?
- Doesn’t truly show the gaps between the atoms
- Doesn’t truly show the correct scales of the molecules
What is a covalent bond?
A strong bond that forms when a pair of electrons is shared between two atoms
What are the properties of a simple molecular substances?
Low melting/boiling point
Unconductive
Some are soluble, some aren’t
Why do simple molecular substances have low melting/boiling points?
Although they have strong covalent bonds between the atoms, the actual intermolecular bond between the molecules is week
To melt/boil, only those weak intermolecular bonds must be broken
What happens to the melting/boiling point as you increase the size of a covalent molecule?
As you increase the size of a covalent molecule, the melting/boiling point increases this is because the intermolecular forces increase strength so more energy is needed to break them
Why don’t covalent substances conduct?
No free ions or electrons
What bonds are found between monomers to form a polymer?
Covalently bonded carbon atoms
What are the bonds in giant covalent structures?
Strong covalent bonds between each atom
What are the properties of a giant covalent substances?
Very high melting/boiling points
Unconductive
Not soluble
Why do giant covalent substances have very high melting/boiling points?
A lot of energy is needed to break the strong covalent bonds
Why are giant covalent substances unconductive?
They, usually, don’t have free electrons
Give 3 examples of giant covalent substances?
Diamond, graphite and graphene
What are diamonds made up of?
A network of carbons that each form four covalent bonds
What are the properties of diamond?
High melting/boiling point
Really hard
Unconductive
Why does diamond have a high melting/boiling point?
The strong covalent bonds require a lot of energy to break
Why is diamond really hard?
The strong covalent bonds hold the atoms in a rigid lattice structure
Why doesn’t diamond conduct?
No free electrons or ions
What is graphite made up of?
Hexagonal sheets of carbon atoms that form three covalent bonds
What are the properties of graphite?
Slippery
High melting point
Conductive
Why is graphite slippery?
No covalent bonds between the layers, only held together weakly so the layers are free to move over each other
Why does graphite have a high melting/boiling point?
The covalent bonds in the layers need lots of energy to break
Why is graphite conductive?
Three out of four electrons are used in bonds, the last is delocalised and can move
What is graphene made up of?
A sheet of carbon atoms joined together in hexagons (one layer of graphite)
True or False? Graphene is a 3d compound?
False, it is two-dimensional as it is one atom thick
What is diamond used for?
Cutting tools (saw teeth and drill bits)
What is graphite used for?
Electrodes or a lubricating material
What do fullerenes form?
Spheres or tubes
What are fullerenes?
Molecules of carbon shaped like closed tubes or hollow balls
What can fullerenes be used to do with other molecules?
Cage the other molecules
What can fullerenes be used for?
To deliver a drug directly to cells in the body
What makes fullerenes a great industrial catalyst?
Fullerenes have a huge surface area
True or False? Nanotubes are also fullerenes?
True
What are the properties of nanotubes?
Conductive
High tensile strength
What does nanotubes having a high tensile strength mean?
They can be used to strengthen materials without adding much weight
What are the properties of buckminsterfullerene?
Stable molecule
Forms soft brownish-black crystals
What shape does buckminsterfullerene form?
A hollow sphere
What does metallic bonding involve?
A delocalised electron
True or False? Metals aren’t a giant structure?
False
What compounds are held together by metallic bonding?
Elements and alloys
What produces all the properties in a metallic bond?
The delocalised electron
What are the properties of a substance that is metallically bonded?
Very high melting/boiling points
Heavy (very dense)
Very good conductive
Some malleable and ductile
Why do metallically bonded substances have a high melting/boiling point?
They have strong electrostatic forces between the metal ions and the delocalised sea of electrons are very strong which means a lot of energy is needed to break these bonds
Why can metals be ductile/malleable?
The layer of atoms in a pure metal can slide over each other
What does malleable mean?
Can be hammered into a shape
What does ductile mean?
Can be rolled into flat sheets
Why are metals good conducters?
The delocalised electrons can carry electrical current and thermal energy through the material
What are usually properties of non-metals?
Dull looking Brittle Lower melting/boiling point Don't usually conduct Lower density
What is the pH scale a measurement of?
How acidic or alkaline a solution is
What pH is neutral?
7
What pH is acidic?
<7
What pH is alkaline?
> 7
What ions do acids form?
H+
What happens to the pH as the concenration of hydrogen ions increases?
It decreases (more acidic)
What is a base?
A substance that reacts with an acid to produce a sold or water
What is an alkali?
Any base that is soluble in water
What ions do alkalis form?
OH-
What happens to the pH as the concenration of hydroxide ions increases?
It increases (more alkaline)
What is an indicator?
A dye that changes colour depending on whether it’s above or below a certain pH
How do you use an indicator?
Add a few drops
Compare result to a pH chart for that indicator
State three examples of indicators for acids and alkalis
Phenolpthalein, methyl orange and litmus
What colour does phenolpthalein turn in acidic conditions?
Colourless
What colour does phenolpthalein turn in neutral conditions?
Colourless
What colour does phenolpthalein turn in alkaline conditions?
Pink
What colour does methyl orange turn in acidic conditions?
Red
What colour does methyl orange turn in neutral conditions?
Yellow
What colour does methyl orange turn in alkaline conditions?
Yellow
What colour does litmus turn in acidic conditions?
Red
What colour does litmus turn in neutral conditions?
Purple
What colour does litmus turn in alkaline conditions?
Blue
What is the reaction between an acid and a base called?
Neutralisation
What does a neutralisation produce?
Salt and water
Is calcium oxide a base or alkali?
A base as it is insoluble
When investigating the neutralisation reaction between calcium oxide and dilute hydrochloric acid, what apparatus do you use to apply the HCL to a conical flask?
Measuring cylinder or a pipette
When investigating the neutralisation reaction between calcium oxide and dilute hydrochloric acid, what is the independent variable?
Mass of calcium oxide
When investigating the neutralisation reaction between calcium oxide and dilute hydrochloric acid, what is the dependent variable?
pH
When investigating the neutralisation reaction between calcium oxide and dilute hydrochloric acid, what do you do once added the base?
Wait for the base to completely react and then measure the pH
How do you know all the base has reacted with the acid?
As base’s are insoluble you’ll know when all the acid has been used up when the base sits at the bottom of the flask
True or False? Not all acids can ionise (dissociate)?
False, all acids can ionise in solution
What does dissociate mean?
Splitting up to produce a hydrogen ion
Define a strong acid
Strong acids ionise almost completely in water
Define a weak acid
Weak acids only partially ionise in water
What does acid strength tell you?
What proportion of the acid molecules ionise in water
What does acid concentration tell you?
How watered down your acid is (how many acid particles there is in a specific volume of water)
What happens to the pH of a substance if it’s concentration of H+ ions increased by 10?
It will be decreased by 1
Give examples of strong acids
Sulfuric, hydrochloric and nitric acid
Give examples of weak acids
Ethanoic, citric and carbonic acid
What is the equation for acid + metal oxide?
Acid + Metal Oxide -> Salt + Water
What is the equation for acid + metal hydroxide?
Acid + Metal Hydroxide -> Salt + Water
What is the equation for acid + metal?
Acid + Metal -> Salt + Hydrogen
What is the equation for acid + metal carbonate?
Acid + Metal Carbonate -> Salt + Carbon Dioxide + Water
How do you test for carbon dioxide?
Bubbling the gas through
If it turns cloudy, carbon dioxide is present
State the insoluble salts of chlorides
Silver and Lead
State the insoluble salts of sulfates
Lead, Barium and Calcium
State the soluble salts of carbonates/hydroxides
Sodium, Potassium and Ammonium
How do you prepare a pure, dry sample of an insoluble salt?
Via a precipitation reaction
When making insoluble salts, what do you add to the lead nitrate?
Water (deionised)
Why do you add water to lead nitrate when making insoluble salts?
To ensure there are no other ions about
What do you do once sodium chloride and lead nitrate are added together when making insoluble salts?
Filter the filtrate
Where do you leave the lead chloride once filtered?
In an oven to dry
Why do you speed up the acid in a water bath when making soluble salts?
To speed up the reaction between the acid and the insoluble base
How will you know when the base is in excess?
Once all the acid has been neutralised the excess solid will just sink to the bottom
What do you do once solid is in excess?
You filter off the excess solid leaving only the salt and water
Once filtered the excess solid, what do you do when making soluble salts?
Heat the solution gently and leave in a dry place to crystallise
What apparatus do you need when making soluble salts using acid and alkali?
Pipette and a burette
What’s one disadvantage to using alkalis to making a soluble salt over base?
There’s no signal that all the acid has been neutralised
Roughly describe how to make soluble salts using acid and alkali?
Using a pipette, measure out a set amount of acid
Slowly add alkali using a burette until you reach the end point
Repeat but without indicator
The solution that remains will only contain salt and water
Slowly evaporate off the water and then leave to crystallise
Filter off the solid and dry it
What is the end point?
When the acid’s been exactly neutralised and the indicator changes colour
What determines how reactive a metal is?
How readily the metal loses it’s outer electrons
What are the physical properties of group 1 metals?
Low melting/boiling points (relative to other metals)
Very soft
What happens when alkali metals are put in water?
They react vigorously
What is the equation when a metal reacts with water?
Metal + Water -> Hydroxide Salt + Hydrogen
How do you test for hydrogen?
Lit splint will make a squeaky pop
True or False? Halogens don’t exist as diatomic molecules as they can’t bond with each other?
False, all halogens exist as diatomic molecules
Describe chlorine at room temperature
Reactive and poisonous, green gas
Describe bromine at room temperature
Poisonous, red-brown liquid which gives off an orange vapour
Describe iodine at room temperature
Dark grey crystalline solid which gives off a purple vapour
What are the patterns as you go down the halogens?
Less reactive
Darker colour
Melting point increases
How do you test for chlorine?
By holding a damp blue litmus paper over and if it turns red chlorine is present as chlorine in a solution is acidic
Why does reactivity decrease in the halogens?
As you go down, the outer shell is further away from the nucleus meaning there is less electrostatic forces of attraction to that shell
To gain an electron the nucleus must, using electrostatic forces of attraction, pull the electron into orbit
Therefore, the less the force of attraction, the harder it is to attract that electron
When metals react with halogens what is formed?
Metal halide (eg sodium chloride)
What is a displacement reaction?
A reaction where a more reactive element displaces a less reactive element from a compound
What type of reactions are displacement reactions?
Redox
Why are displacement reactions redox?
Because the more reactive element gains an electron/s (reduction) whilst the less reactive element, the one in the compound, loses electron/s (oxidation)
What are the properties of group 0 elements?
Inert
Colourless
Gases
True or False? Noble gases are monatomic?
True, they are unreactive and have a full outer shell therefore they do not need to diatomically bond
What are uses of argon?
Filament lamps
What are the uses of helium?
Airships, balloons and metal protection
Define rate of reaction
How quickly a reaction happens
What are the two ways of measuring reaction rate?
How quickly the reactants are used or how quickly the products are formed
What is the rate of reaction equation?
Amount of reactant used or amount of product formed / Time = Reaction Rate
What are the three ways of measuring reaction rate?
Precipitation, change in mass and volume of gas given off
Roughly describe how to measure rate of reaction via precipitation
Mix solutions which produce precipitate
As the precipitate forms, observe the mark and time how long it take’s for the mark to be obscured
What is a downside to using precipitation to measure rate of reaction?
Result is subjective - different people might not agree on exactly when the mark disappears
Roughly describe how to measure rate of reaction via change in mass
Measure mass before reaction
Let reaction finish and then calculate mass change
When measuring rate of reaction via change in mass how can you tell the reaction has stopped?
When the balance stops changing
What is a downside to using mass change to measure rate of reaction?
If harmful gas is produced, you must take safety precautions
Roughly describe how to measure rate of reaction via volume of gas
Let reaction finish and then calculate gas volume change using gas syringe
What is a downside to using volume of gas change to measure rate of reaction?
If not right size gas syringe chosen, plunger may be pushed out the end
When measuring rate of reaction using gas volume, what are the control variables?
Same volume of acid
Same mass of marble chips
How does surface area affect reaction rate?
The finer the particle, the faster the rate of reaction
How does concentration affect reaction rate?
The more concentrated the solution is, the faster the rate of reaction
How does temperature affect reaction rate?
The higher the temperature, the faster the rate of reaction
What solutions are used when using precipitation to measure reaction rate?
Sodium thiosulfate and hydrochloric acid
What colour precipitate will sodium thiosulfate and hydrochloric acid make?
Yellow
What are two control variables when measuring rate of reaction through precipitation?
Depth of liquid
Volume of liquid
What does the rate of reaction depend on?
The collision frequency and the energy transferred during a collision
Define a sucessful collision
A collision that ends in the reactants forming the products
How does temperature increase rate of reaction?
Increases energy in particles - increases frequency of successful collisions
Increases particle movement - increases frequency of collisions
How does concentration of reactants increase rate of reaction?
Increases number of particles - increases frequency of collisions
How does surface area increase rate of reaction?
Increased surface for reaction to occur - increases frequency of collisions
What does a catalyst do?
Increases the rate of a reaction without being used up or chemically changed
What is an enzyme?
A substance that will increase the rate of reaction without being chemically changed or used up in the reaction
How does the enzyme affect the reaction equation
Has no affect so equation will remain the same
How do catalysts work?
By decreasing the activation energy by providing an alternate reaction pathway
Why do catalysts speed up the rate of reaction?
Decreases acvtiation energy
More particles have at least the activation energy
Therefore there will be a increased frequency of successful collisions
What are biological catalysts?
Enzymes
Give an example of when enzymes are used?
Respiration, photosynthesis and protein synthesis
What is an exothermic reaction?
A reaction which gives out energy to the surroundings, usually in the form of heat
What is an endothermic reaction?
A reaction which takes in energy from the surroundings, usually in the form of heat
What is activation energy?
The minimum amount of energy needed for bonds to break and a reaction to start
What will happen if energy input is less than activation energy?
Reaction won’t start, so nothing will happen
How do you measure temperature change?
Polystyerene cup in a large beaker of cotton wool Add a known volume of your first reagent Measure inital temperature Add second reagant and stir Record final temperature Calculate temperature change
What type of reaction is dissolving salts in water?
Both endo and exothermic
What type of reaction are neutralision reactions?
Mainly exothermic
What type of reaction are displacement reactions?
Exothermic
What type of reaction are precipitation reactions?
Exothermic
Describe what happens to bonds during chemical reactions
Old bonds are broken, new bonds are formed
What type of process is bond breaking?
Endothermic
What type of process is bond forming?
Exothermic
Describe the bond energies in endothermic reactions
Energy releleased by forming bonds is lower than energy used to break them
Describe the bond energies in exothermic reactions
Energy releleased by forming bonds is greater than energy used to break them
What is the overall energy change equation?
Overall Energy Change = Energy required - Energy released
What does the sign of the value for overall energy change tell you?
-ve = exothermic \+ve = endothermic
