Science Help Please

Hey, I need to know the best way to revise for a Gcse practical experiment and the test that you sit with in Science. I need to revise 'How science works' and could do with some good websites. Also, i need to know the difference between precise and accurate. I also need to know all the possible graphs I could do for my coursework and which variables determine which graph I need to use. I know for a categoric independent variable I must produce a bar graph to show my data. I also know that continuous independent variables require a line graph. But where do scatter graphs come in. And would you regard discreet variables and ordered variables as categoric variables? Is there anything else useful I should know? I also need a good explanation of what a Control Variable is as I am struggling to understand its definition. Help would be appreciated loads and thank you in advance.

BelieveandSucceed
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our school's key word sheet for ISAs, i'm guessing you are yr10/11? They tweaked the key terms for the new AQA spec.

• In everyday language the word theory means something rather uncertain – a hunch e.g. “I have this theory about him/her”. In science the word theory is used very differently to this and is much more robust. In science, something is only called a theory if it:
1. explains a wide range of things;
2. makes predictions that can be tested;
3. is falsifiable i.e. could be shown to be false. Darwin’s theory of evolution could be shown to be false if, for example, fossilised human footprints were found in the same layer of ancient rocks as dinosaurs.
• An independent variable is what you deliberately change to see the effect it has.
• The dependent variable is what you measure each time you change the independent variable.
• The control variables should be kept constant otherwise they might affect the results and make conclusions invalid. If it is impossible to control something then it should be monitored. A control group is often used in testing new drugs, and involves them being given placebos (dummy drugs).
• A continuous variable is one that can have any numerical value, whereas a categoric variable is described only by labels/words.
• An accurate measurement is one which is close to the true value.
• Precision of a measuring instrument is the smallest scale division e.g. most rulers have a resolution of 1mm.
• Reliable results have a small degree of scatter - they are close to the mean value
• Random errors cause measurements to be spread around the true value, often caused by inconsistent measuring techniques.
• Systematic errors cause measurements to be spread about some value different to the true value. A zero error is a type of systematic error e.g. bathroom scales not set to zero before weighing.
• Repeating results or comparing with results obtained by other people makes them more reliable and also enables anomalous results to be easily identified. The sample size needs carefully choosing so as to make the results reliable without being excessive.
• Values are the results/measurements.
• The range is the interval between the highest and lowest value e.g. 120 – 160 cm.
• A measuring instrument is calibrated by marking fixed points on the scale against some standard e.g. 0°C and 100°C on a thermometer.
• A linear relationship is one which produces a straight line on a graph.
• A directly proportional relationship is where there is a fixed ratio between the variables. This causes the graph to be a straight line that passes through the origin (0,0).