At the end of this unit you should:

At the end of this unit you should: 1. Be able to explain the difference between a fuel and a fossil fuel. 2. Be able to describe how different fossil fuels are formed. 3. Be able to test and identify the product of combustion. 4. Be able to test and compare a selection of fuels. 5. Understand that crude oil is a mixture. 6. Understand the differences between fossil fuels and hydrogen fuels cells. 7. Be able to explain that the burning of fuels can be used to create thrust.

aerobic respiration chemical energy coal combustion crude oil fire triangle fossil fuel fracking fuel hydrocarbons methane natural gas oil thrust turf

LIGHTBULB QUESTION The word ‘fuel’ is technically correct when talking about food as energy, which is released from hydrocarbons in food by reacting them with oxygen (respiration), a process broadly similar to combustion. However, not all foods provide energy.

Combustion: The release of heat energy from substances by chemical reaction with oxygen. Aerobic Respiration: The release of energy from nutrients in organisms by chemical reaction with oxygen.

Chemical Energy: The stored energy in chemicals that can be released in reactions. Fuel: A substance that releases its chemical energy as heat energy when reacted with oxygen.

(a) Below are the chemical equations for a combustion reaction and a respiration reaction. Complete these reactions by filling in the blanks.

(b) All three parts of the fire triangle must be present for a combustion reaction to happen. Which part of the fire triangle is missing from the combustion reaction above? The fuel.

Fossil Fuel: A fuel based on animal and plant remains that is extracted from the earth. Hydrocarbons: Compounds that are made only of hydrogen and carbon atoms.

Investigation 09.02.01: Chemical identification of combustion products Equipment: Two large test tubes, two two-hole rubber stoppers, filter funnel, tea-light candle, methylated spirits burner, wooden splint, petri dish, test tube rack, rubber tubing, glass tubing, suction pump, anhydrous copper sulfate, limewater.

Instructions: 1. Light the tea-light candle and allow to burn for several minutes. 2. Set up the apparatus as shown, making sure that the anhydrous copper sulfate is placed in a clean, dry test tube. 3. The test tubes can be placed in a test tube rack (or set up in clamps on a retort stand). 4. Make sure that the suction pump is securely attached to a tap. 5. Turn on the tap fully to ensure that air is sucked through the apparatus. 6. Place the candle under the funnel, and observe any changes that occur. 7. Clean out each of the test tubes and repeat the procedure with a methylated spirits burner. 8. The procedure should be repeated for a lit wooden splint. The splint can be set in a petri dish (or clock glass).

1. What products of a combustion reaction can be identified by simple tests? • Carbon dioxide by passing through limewater, and oxygen by testing with a glowing splint.

2. How are the samples of the combustion products captured in the first place? Can you think of a better way to capture them? • The first test tube could be submerged in ice water to ensure that water vapour does condense. This could also be compared against the water vapour condensation of the air before combustion.

3. Is this method suitable to test a range of different combustion reactions? How do you know this? • The positive test results from three different fuels show that this method is useful across a range of fuels. But to have a fair test there should be the same mass of fuels and they should be in the same state and particle size to minimise surface area differences.

(a) Coal has been mined and peat harvested for centuries in Ireland. Oil and gas have never been discovered on this island except in small pockets. Based on the plant and animal origins of fossil fuels, what can you say about the surface terrain of Ireland in ancient times? A lot of the land of ancient Ireland was swampy.

(b) Fossil fuels can be solids, liquids or gases. Which state of matter do you think releases more energy? Justify your answer. Solids will release the greatest amount of energy as they are more dense. This means that 1 cm3 of coal contains more molecules than 1 cm3 of oil or gas. But liquids and gases may release a lot of energy quickly because their particles are held further apart. However, the total energy released by a solid when burned is always greater regardless of how fast it is released.

DEMONSTRATION Demonstration 09.02.01 – Faraday’s candles Equipment: Two candle sticks, two candle stick holders, matches.

DEMONSTRATION Instructions: 1. Two candles, A and B, should be lit near each other and allowed to burn for approximately five minutes. 2. Candle A should be blown out and the flame of Candle B positioned 10–15 cm directly above Candle A. 3. Record your observations.

1. If you were to repeat this demonstration, what steps (actions) would you take to make it a successful demonstration? • There are a few factors you could thinks about for example: • the distance between the two candles • or how long they were lighting initially. • What other factors can you think of ?

2. Can you put together a scientific explanation for how a flame can transfer from one candle to another? • The flame does not relight ‘by magic’. Can you think of a way that the ‘fuel’ for the flame might have filled the gap between the lit and unlit candle? Particle theory can be used in your explanation.

3. Why might this be important in coal mines, saw mills and flour mills? • In the last question you came up with a way of explaining how the ‘fuel’ for the candle flame got into the gap between the candles. What fuel can get into the air in mines, saw mills and flour mills, and is this an important thing to remember if you work in one of these places?

Investigation 09.02.02: Comparing the energy content of three fuels Equipment: Retort stand with two clamps, thermometer, two spirit burners (or two microburners), cotton twine, 100 ml conical flask, two 50 ml graduated cylinders, top-pan balance, methanol, propanol (propan-1-ol), two tea-lights (or two small/cut-down candlesticks), 15 cm ruler, scissors, roll of aluminium foil, two pieces of card (15 cm x 15 cm) acting as draught excluders, four brass slotted weights, filter funnel, matches.

Investigation 09.02.02: Comparing the energy content of three fuels

Instructions: 1. Wrap two 15 cm x 15 cm pieces of cardboard in aluminium foil. Slot each card into two slotted weights to stand upright to act as draught excluders. 2. Remove a tea-light candle from its container and find the total mass of the wax and its wick using the top-pan balance. Record this mass. 3. Place the tea-light candles back into their containers. 4. Transfer methanol with a mass equivalent to the mass of the tea-light candle into the spirit burner. 5. Record the total mass. Label the spirit burner ‘M’. 6. Transfer propanol with a mass equivalent to the mass of the tea-light candle into the spirit burner.

Instructions: 7. Record the total mass. Label the spirit burner ‘P’. 8. Transfer 50 ml of tap water to the conical flask and clamp the flask so that it is 8 cm above the rim of the tea-light candle. 9. The same distance should be set from the rim of the spirit burner when testing the liquid fuels. 10. Fix the thermometer in a second clamp so that it sits deep in water without touching the glass walls of the flask. Record the initial temperature of the water in the flask. 11. Set the draft excluders either side of the apparatus. 12. The candle should be lit and allowed to burn for 5–10 minutes. Note the final temperature of the water. 13. Place the tea-light candle aside and allow to cool.

Instructions: 14. Empty the conical flask, and clean any soot from the outside. Refill with 50 ml of tap water. 15. Set the methanol burner underneath the conical flask. Adjust the clamp height so that the bottom of the flask is 8 cm above the rim of the burner. 16. Record the temperature of the water in the flask. 17. Light the burner and allow to burn for 5–10 minutes. Note the final temperature of the water. 18. After quenching the burner, find its new total mass and calculate the mass of methanol used. 19. Repeat the same process for propanol. 20. Use a forceps to remove the tea-light candle from its holder and find its new mass. Calculate the mass of candle burned.

1. How can you make sure that you are comparing each fuel fairly? • As solid and liquid fuels are being compared, an equal mass of each is burned over a fixed time period, heating an equal mass of water. Using a microburner/DIY burner eliminates the skewing effect of different wick diameters.

2. Is there another way of comparing these fuels using similar equipment? • The conical flask could be replaced by a round-bottomed flask or even a tin can or large boiling tube. Rather than taking a specific temperature, the speed at which a fixed mass of an easily melted solid such as butter or chocolate melts (sitting on a clock glass above the flame) could be calculated. Similarly a beaker with a fixed mass of ice could be used to see how much of the ice melts over a fixed time. The volume of water from each fuel test could simply be poured into a graduated cylinder.

3. Which of these fuels are fossil fuels? • The paraffin wax, as it is refined from crude oil. • 4. Is there a simple way to tell the difference between a fossil fuel and another fuel? • No – the effectiveness of fuel depends on the number of carbon atoms it contains. The more carbon atoms, the greater number of bonds, so more energy can be potentially released during combustion.

5. What do fossil fuels and other fuels have in common? • They release heat and light energy when combusted and contain a large number of carbon atoms compared to other substances.

Table 09.02.01 shows four fuels. Match the correct fuel to each device. Bunsen burner – methane (natural gas). Disposable cigarette lighter – butane. Brûlée torch – butane/propane. Camping stove – propane.

(b) Does the number of carbon atoms in a fuel have any effect on how that fuel burns? Reflect on the results of your investigations. Yes – the longer the carbon chain, the better the fuel. Heat energy is released in chemical reactions when the breaking up of the reactants releases more energy than the formation of the products. If there are more carbons in a substance, there are more bonds that can be broken, as every carbon can link to four other atoms. This means that carbon can form long stable chains.

Extraction of oil from the earth Unconventional well Oil and gas are accessible using horizontal drilling and hydraulic fracturing Conventional well Oil and gas are accessible using vertical drilling Fracturing fluid ❹Oil or gas collected and transported ❶Fracturing fluid containing water, sand and chemicals is injected at high pressure. Drinking water aquifers Depth less than 150m ❷Rock is cracked open (fractured), releasing the oil or gas inside. ❸ Flow-back water is recovered Highly impermeable rock Depth 1,000m – 4,000m

List and describe two environmental impacts from oil and gas extraction. • Pollution: • Oil leakage around the well (soil pollution) • Potential contamination of water supplies or rivers • Gas burn-off adds to greenhouse gases in the atmosphere • Noise and light pollution from twenty-four-hour operations can disturb the natural rhythms of local organisms. • Habitats: • Organisms in vulnerable areas can be harmed if feeding or breeding zones are affected • Unique habitats can be destroyed. • Earthquakes: • Rock layers can be destabilised, causing mini-earthquakes.

(b) Peat is extracted on a very large scale in both Ireland and large parts of Russia. What effect do you think peat extraction may have on the environment? As well as increasing air pollution levels, it damages habitats that can take thousands of years to recover, meaning that there could be local extinction of some organisms.

(c) Coal was a very common fossil fuel in Ireland for most of the last two centuries. Why is it no longer used so much? A ban on using coal (a smoky fuel) started in 1990 because smog was causing serious health problems in the Dublin area. This ban was extended to other parts of the country over time. This has made the burning of coal in some areas illegal, so has reduced the demand for coal. People have also realised that it is less damaging for the environment to use other fuels for heating.

C1 to C4 ‘Refinery gas’ (petroleum gas) = 25°C ❸ The shortest carbon chains have the lowest boiling points. C5 to C9 Decreasing temperature Petrol (light gasoline) = 50°C ❷ The temperature drops as the oil fractions move up the tower. This means only the fractions with the lowest boiling points are carried to the top by convection currents C5 to C10 Naphtha = 100 °C C10 to C16 Kerosene (paraffin) = 200°C C14 to C20 ❶ The crude oil is passed through a pipe which is heated by the furnace Diesel oil (gas oil) = 300°C C20 to C50 FURNACE Lubricating oil = 400°C C20 to C70 Fuel oil = 450°C CRUDE OIL Fractionating column > C70 Bitumen > 500°C

DEMONSTRATION Demonstration 09.02.02 – Burning ice Equipment: Crystallising dish, weigh boat, top-pan balance, 1.5 g of calcium carbide (CaC2), ice cubes, matches, six wooden splints, 3.0 M hydrochloric acid.

DEMONSTRATION Instructions: Place a clean, dry crystallising dish in a fume hut and sprinkle the calcium carbide across its base. Fill the dish with ice. Light the ice using a burning splint. If the ice stops burning, allow some acetylene gas to be formed and relight. Relight until all the gas has been exhausted. The gas may not burn evenly and may therefore ‘pop’ as it is burning. A base is formed during this reaction, which can be neutralised by adding 3.0 M hydrochloric acid, before flushing with excess water down a waste drain. Universal pH paper can be used to check for neutralisation before disposal.

Thrust: The force created by rocket engine exhaust gases.

DEMONSTRATION Demonstration 09.02.03 – Mentos reaction Equipment: Two-litre bottle of diet cola, bulldog clip, paper clip, fishing line, retort stand and clamp, heated probe (or needle), six Mentos sweets.

DEMONSTRATION Instructions: 1. Open up a standard size paper clip until there is a hook at one end. 2. Heat the tip of the probe and use it to make a hole in the bottle cap. 3. Use the probe to pierce the centre of each Mentos sweet. 4. The Mentos sweets can be placed on the paperclip skewer. 5. The cap can then be added to the skewer with a small amount of the paperclip skewer protruding. 6. A length of fishing line (or twine) can be tied to the bulldog clip. 7. The bulldog clip can be attached to the protruding end of the paperclip skewer. 8. The capped skewer can now be screwed into position. 9. Retreat to a distance of about 3 metres and pull sharply on the fishing line to release the bulldog clip.

1. Based on your observations, do you think that a DIY rocket could be made from this equipment? Explain. • Yes – it creates enough thrust to lift the mass of the soft drinks bottle, especially as the bottle will empty as the reaction continues.

2. How could you make sure that the rocket moves upwards, without causing damage or injury? • A small mass could be taped to the bottle near the top of the rocket (bottom of the inverted bottle), which would cause the bottle to tilt as it lifts off . This gives crude direction to the rocket.

DEMONSTRATION Demonstration 09.02.04 – Electrohydrolysis Equipment: Hofmann’s voltameter, 0.3 M sulfuric acid, liquid universal indicator, 6V cell, two cables, distilled/deionised water, stirrer, 400 cm3 beaker, filter funnel.

DEMONSTRATION Instructions: 1. Make sure that the electrodes are secured into the bottom of the Hofmann’s voltameter. 2. Add 25 cm3 of 0.3 M sulfuric acid slowly to 200 cm3 of distilled/deionised water, stirring to ensure mixing. 3. Open the valves of the voltameter. 4. Add the acidified water solution to the voltameter, allowing trapped air to rise to the surface through the taps or reservoir. Close the taps. 5. If necessary, add more distilled/deionised water to fill the reservoir above the central feed tube.

DEMONSTRATION Instructions: 6. Connect the electrodes to a 12V DC supply to ensure quick electrohydrolysis. A 6V cell may be used but the electrohydrolysis takes much more time. 7. If needed, a stoppered side-arm test tube with a rubber delivery tube and Hofmann clip can be used to collect the gas from each tap and test it (see diagram).

1. Explain why this experiment won’t work unless the water is acidified. • There is not enough charge difference in pure water for electrons to flow.

2. How is it possible to tell the difference between the two gases produced by this method? • Both gases can be tested: a glowing splint will relight in oxygen and a burning splint will burn with a ‘pop’ in hydrogen.

3. Do the amounts of each gas tell us anything about water? • The volumes of gas give us the ratio of hydrogen to water, which means that for each oxygen there is two hydrogens. This means that the formula of water is possibly H4O2 or even H20O10. Using x-rays of water crystals, William H. Barnes proved that a single molecule of water was actually H2O.

At the end of this unit you should: