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| Question | Answer |
| These cards are for the OCR 21st Century Science Course, and they are complete. ... | They're neither easy nor impossible, and you're very welcome to use them! |
| What is the atmosphere? | A layer of gases that surround the earth. |
| Name the major two gases and their percentages in normal air quality. | Nitrogen - 78% Oxygen - 21% |
| What are the main air pollutants? (There are 5!) | Sulfur dioxide. Carbon monoxide. Carbon dioxide. Nitrogen dioxide. Particulates. |
| How is air quality measured? | By the concentration of pollutants in the certain volume of air measured. |
| What 2 factors influence air quality, with examples? | Sources - industry, vehicles, power stations. Weather - dependant on whether the pollutants are being blown in or out of the area. |
| What was earth's early atmosphere like? | Mostly carbon dioxide and water vapour, some nitrogen and methane, a tiny bit of oxygen. |
| Why is it important to repeat an experiment? | To get an accurate reading. If the data isn't repeated, there's no way of confirming whether your result is an outlier or not. |
| How do you know if your data is accurate? | You never know for sure but if you've repeated the experiment many times and have the mean this is a good result. If your range is very small, your data is more accurate as well. |
| What is a change that forms a new chemical called? | A chemical change or a chemical reaction. |
| When coal is burned in a power station, it produces CO2. Why is this? | Coal is mostly carbon (C) and when this burns it combines with oxygen (O). The gas escapes as CO2. Oxygen is needed for a fire to stay alight. |
| In a gas-fired power station CO2 and H2O are produced - where does the water come from? | Gas is a hydrocarbon (CH4). When CO2 is produced the hydrogen is left over so it combines with oxygen. |
| Why does sulfur dioxide (SO2) sometimes form when coal or gas are burned? | Fuel's often contain sulfur as an impurity. This oxidises in the furnace. |
| In a reaction what are carbon and oxygen called? What is carbon dioxide called? | Carbon and oxygen are reactants. Carbon dioxide is the product. |
| What is a correlation? | A link between two things. If an outcome increases/decreases as a factor increases and you can provide evidence the link is more than a coincidence. |
| What is a cause? | When there is evidence that changes in a factor produce a particular outcome. For example, increase in pollen causes hayfever. |
| How does a catalytic converter work? | It has a large surface area becomes of its honeycomb structure. The pollutants use the metal surface to join up on - for example 2CO + O2 = 2CO2 |
| How is sulfur dioxide removed, as much as possible, from power station emissions? Aside from refining the material before burning? | Wet scrubbing - an alkali such as seawater or calcium oxide is reacted with the flue gases. The droplets or solids respectively are collected before the cleaned gases are released. |
| How are particulates removed from waste gases? | The particulates are passed through a negatively charged grid. They then get attracted to the positively charged collecting plates on the wall. |
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