Command words and Key words Command words are the words and phrases used in exams that tell students how they should answer a question. Hypothesis A scientific statement that explains certain facts or observations Anomaly A result that does not fit the pattern Prediction This describes what you think will happen in an experiment Accuracy How close the reading is to the true value variable This is the variable that is changed during an investigation. There should only be one of these. True This is the real value of a measurement in an experiment Dependent variable This is the variable that changes as a result of a change in the independent variable Precision This is determined by the on the measuring apparatus e.g. a ruler marked mm is more precise than one in cm Control variable Variables that remain constant, to make sure that an investigation is valid Resolution The smallest change that can be read from a measuring device for example a ruler measured in mm or cm Fair test This is only the independent variable is changed and the others controlled Calibration When we make sure that measuring apparatus is making correct readings e.g. the temperature of melting ice is 0 degrees Celsius Valid The results and conclusions will be this if the variables are correctly controlled Measurement error The difference between the real value and the measured value Categoric variable A variable that can be described by a or category such as colour or surface Random This error causes measurements to be spread around the true value – can be reduced by taking repeats and calculating a mean Continuous variable A variable which can have any numerical value Zero error When a piece of measuring equipment should be reading zero but it doesn’t Interval This is the difference between the values of your independent variable Systematic error This is an that is always the same for each repeat – usually because of an error in the equipment used Range The maximum and minimum values of the independent or dependent variables e.g. ‘from 10cm to 50cm’ Uncertainty When the results obtained are not as accurate as they could be due to the procedure carried out Data Information or measurements that you collect Repeatable If the same person can get the same reading using the same equipment and method Datum One of information Reproducible If another person can get the same result (trend/specific results) using the same method and equipment or with different method or equipment.
Calculate Use numbers in the question to work these out. Draw Produce, or add a diagram. Choose Select from a range of alternatives. Estimate Give an approximate Compare Describe similarities/differences. Use The answer must include the information in the question. Define Specify the meaning of something. Work out Students should use numbers in the question. Describe Recall facts, events or process in an accurate way. Write answer, no explanation or description. Design Set out how something will be done. Evaluate Students should use the information provided as well as their own knowledge and consider evidence for or against. Determine Use the data provided to work out your answer. Explain Students should make something clear, or state reasons for something happening. Give Short answer only. Identify Name or characterise. Label Justify Use evidence from the information supplied to support your answer. Measure Find an item of data for a given quantity. Name Single word or phrase. Plot Mark on a graph. Plan Write a method. Predict Give a plausible outcome. Show Provide structures evidence to reach a conclusion. Suggest Apply your won knowledge. Sketch Draw approximately. Use of apparatus and techniques