A pure substance is made from only one compound or just one element with no other substances mixed in.
They melt at a specific fixed temperature
They boil at a specific fixed boiling point
It is a complex mixture designed as a useful product
Fuel
paints
medicines
Paper chromotography allows us to seperate mixtures based on their different solubilities
The paper is called the stationary phase as it does not move
The solvent is described as the mobile phase because it does move
A pure substance will produce a single spot in all solvents
Compunds in a mixture will seperate into different spots depending on the solvent
If the line were drawn in pen the ink would move up the spaper with the solvent
Distance moved by substance
------------------------------------- = Rf value
Distance moved by solvent
It helps find unkown chemicals by finding the Rf value on a database to find that substance
Several different substances could have the same rf value so we might have to repeat the experiment with a different solvent
If the substance has never been analysed before then there will not be an Rf value on the database
1.Use a ruler to draw a horizontal pencil line on the chromatography paper, it should be around 2cm from the bottom of the paper.
2.Mark equal pencil spots for how many substances you are testing. leave at least 1cm per pencil spots, keep the spots relatively small to prevent them from spreading onto each other.
3.Use a capillary tube to put a small spot for each known food colours and unkown food colours onto the pencil spots.
4.Pour the solvent into a beaker with a depth of 1cm.
5. Attach the paper onto a glass rod using tape and lower the paper into the beaker containing the solvent, the bottom of the paper should dip into the solvent.
6.The solvent will then go up the paper and so will the ink. During this stage it is important not to move the beaker.
7.Remove the paper when the solvent has travelled 3 quaters up and use a pencil to mark the point where the solvent has reached
8. lastly hang the paper up to dry
The pencil lines with the spots of ink must be above the surface of the water other wise the water will wash the ink of the line
The sides of the paper must not touch the walls of the beaker as it can intefere with the way the water moves
Usually put a lid on the beaker to reduce evaporation of the solvent
Use a burning splint and hold it at the lid of the test tube. Hydrogen burns rapidly so a squeaky pop sound should be produced
Insert a glowing splint into a test tube. If oxygen is present the test tube should relight
Bubble the through the limewater using a pipette. If carbon dioxide is present the water would turn cloudy
Insert damp litmus paper into the mouth of the test tube. The chlorine should bleach the litmus paper and turn it white
It is formed over millions of years from the remains of tiny see creatures called plankton which were buried in mud
Molecules that are mad up of only carbon and hydrogen atoms
CnH2n+2
The carbon atoms are fully bonded to the hydrogen atoms
It tells us the thickness of a fluid
As the size of the hydrocarbon molecule increases the molecules get more viscous
It tells us how easily something is able to combust
As the size of hydrocarbon molecules inreases, the molecules get less flammable
As the size of hydrocarbon molecules increases so does the boiling point
They release energy when combusted
When a substance is combusting, if enough oxygen is present water and carbon dioxide will be produced
1. The crude oil is heated to a very high temperature causing it to boil
2.The column is cooler on the top and hotter at the bottom. The hydrocarbon vapours now rise up the column
3.The hydrocarbons would condense when they reach their boiling point and the liquid fractions are removed.
4. The remaining hydrocarbons continue moving up the column and these then condense when they reach their boiling points
Very long hydrocarbons have very high boiling points these hydrocarbons are removed from the bottom of the column
They have very low boiling points so they do not condense. They are released at the top of the column as gases
They contain hydrocarbons with a similar number of carbon atoms
Petrol and diesel
liquified petroleum gas
kerosene
heavy fuel oil
They only have single covelant bonds between the carbon atoms
Using high temperature and a catalyst. The catalyst is used to speed up the reaction
Use steam and high temperatures
An alkane and an alkene
They have a double covelant bond between two carbon atoms
They are used to make polymers
Using an alkene and bromine water put both in a test tube and shake it. The bromine water should turn colourless (NOT CLEAR)
quantity of product formed
--------------------------------------------------
time taken
A chemical reaction can only take place when reacting particles collide with each other. These particles must have sufficient energy
The number of successful collisions per second
The rate of reaction is determined by the frequency of the successful collisions
If the concentration of reactants increases the rate of reaction will also increase and vice versa
1. Use a measuring cylinder to put 10cm3 of sodium thiosulfate into a conical flask
2. Place the conical flask on top of a printed black cross
3. Now add 10cm3 of hydrochloric acid into the conical flask
4. Swirl the solution and start a stopwatch
5. Choose a person to look down into the flask. After a certain time, the solution will turn cloudy, stop the stopwatch when we can no longer see the cross
6. Now carry out the experiment again using lower concentrations of sodium thiosulfate.
A measurement is reproducible if it can be repeated by another person or using different equipment or technique and still get the same result
Different people have different eye sights which means that some people may be able to see the cross for longer. This could result in different results being produced
An increase in surface area will mean that there are more particle colliding with the surface of the reactant therefore increasing the rate of reaction and vice versa
If temperature increases the rate reaction also increases. This is because the particles have more energy so they would move faster. This increases frequency of the collisions. Secondly the collisions have more energy meaning that more particles can overcome the activation energy barrier
The minimum amount of energy required for a particle to react
Catalysts speed up the rate of reaction without being used up in the reaction
They speed up the rate of reaction by finding a different pathway for the reaction that requires a lower activation energy.
This is when the product is able to react and form the original reactants
If a reaction is endothermic in one direction then it will be exothermic in the opposite direction. The same amount of energy will be transferred
When the forward reaction and backward reaction take place at the exact same rate in a closed container. The container prevents any gas from escaping.
If a system is at equilibrium and a condition is changed then the system responds to counteract that change
If the concentration of the reactants is raised, the forward reaction will increase its rate in order to balance out the concentration of the reactant and the product. The opposite happens if the concentration of the reactants are decreased
If the concentration of the products is raised the backward reaction will increase its rate of reaction in order to balance out the concentration and reach equilibrium. The opposite happens if the concentration of products is decreased
If the temperature is increased the equilibrium moves in the direction of the endothermic, if the temperature is decreased then equilibrium moves in the direction of the exothermic reaction.
If pressure is increased then the equilibrium will shift to the side with the smaller number of molecules. If pressure is reduced then equilibrium will shift to the side with a larger number of molecules
They cannot be replaced as quickly as they are being used
A resource that is being replaces as we use it
Meeting the needs of today without jeapordising the needs of the future generations
Water that is safe for human consumption
Pure water contains no dissolved substances at all, meanwhile potable water contains small amounts of dissolved substances such as sodium chloride
Find a freshwater source to use. Pass that fresh water source through a filter bed to remove things like leaves and twigs. Then the water is sterilised to kill the microbes using chlorin. Ozone and ultraviolet light can also be used in sterilization
The process of turning salty sea water into potable water
The sewage is passed through a metal mesh removing solids and pieces of grit. The sewage then settles in large sedimentation tanks. This produces a liquid effluent and a semi-solid sludge which sinks to the bottom. The sludge is taken away and digesting anaerobically by specific bacteria to remove organic matter. Air is bubbled through the liquid effluent allowing aerobic bacteria to multiply. In the presence of oxygen the aerobic bacteria digest the organic molecules reducing solid waste. It is then treated with chlorine, ozone or UV light to kill bacteria. It is then safley discharged to the ocean
Plants are grown over an area where the metal compund is present. These plants absorb the metal compound and concentrate it inside their tissue. These plants are then harvested and burned. The ash will contain a relatively high concentration of the metal compound
The bacteria is mixed with the low grade metal ore. They carry out chemical reactions producing a solution called leachate. The leachat will contain the desired metal compund
a process of evaluating the effects that a product has on the environment over the entire period of its life
Environmental impact on extracting and processing the raw materials
Manufacturing of the product along with the packaging of it
Environmental impact upon its life time usage
Assess the disposal of the product at the end of its useful life
78% nitrogen 21% oxygen 0.04% carbon dioxide
During the first billion years scientists think there was heavy volcanic activity which a released a multitude of gases forming the atmosphere. One of these gases was water vapour. Overtime the earth cooled and the water vapour in the air condensed to form the oceans. Large amounts of co2 were contained in the atmosphere due to the volcanos with little to no oxygen present.
CO2 dissolved in the oceans to weak acids. These acids reacted in the minerals in the sea to from percipitates. Over time this formed sediment and carbonate rocks. Some of the CO2 was used to make corals and shells of organisms such as mussels. They formed limestone upon death
Around 2.7b years ago photosynthetic algea evolved in the oceans. photosynthesis produced oxygen and taking in the co2. Over more billions of years plants evolved causing more oxygen to be released and co2 to be taken in
Fossil fuels are formed over millions of years. They are non-renewable and will eventually run out
They are formed from the remains of ferns and trees. If these die in marshy wetlands then they do not decompose dure to either a lack of oxygen or acidic conditions preventing bacteria from carrying out decomposition. Overtime plant remains are covered with sediments and compressed. The high temp and pressure is called coals
Melting of polar ice caps leading to an icrease in sea lelvels inreasing flood risk in low lying areas
More severe weather
Change distrubution of insects and habitats
The total amount of carbon dioxide and other green house gases emitted by the full life cycle of an object service or event
They are produced in the engine of cars. At high temps nitrogen and oxygen in the air react to form Oxides of nitrogen
They are particles of carbon and unburned hydrocarbons. They have respitory risks such as heart and lung disease. They can cause global dimming where they reduce the amount of energy taken in from the suns shortwave radiation wave