Science Practical

• Independent Variable- The variable (factor) you choose to change in an investigation
• Dependent Variable- The variable (factor) which you measure every time you change the value of the independent variable.
• Controlled Variable- A variable which may affect the results of the investigation and therefore should be kept constant
• Range- The highest and lowest values of the independent variable. These should not be too big or too small
• Valid Conclusion- A conclusion supported by the results of data from a well-designed investigation and based on good scientific knowledge.
• Validity of experimental design- How good the method is to answer the question being asked. The method should include fair testing and controlled variables
• Resolution- This is the smallest change in the quantity being measured by a certain measuring instrument which can be observed. For example +1mm on a 1 metre ruler.
• Anomaly- A value in a set of results which is seen to be much bigger or smaller than the rest of the values in the set.
• True value- This is the value that would be obtained in ideal conditions.
• Measurement error- the difference between the measured value and the true value of the variable.
• Systematic error- Normally caused by the apparatus used and causes readings to differ from the true value by the same amount each time. The effect of systematic errors cannot be reduced by increased repeats
• Random error- This occurs when results vary unpredictably from one measurement to the next. These are normally due to human errors. The effect of random errors can be reduced by taking more measurements and calculating a mean.
• Accuracy- A measurement result is considered accurate if it is judged to be close to the true value.
• Precision- A set of precise measurements show very little spread about the mean value.
• Repeatable- A measurement is repeatable, if a single learner/ group, using the same method and experiment, obtains the same or similar results when they carry out the investigation again.
• Reproducible- A measurement is reproducible if different learners/ groups obtain the same or similar results. Could include using different equipment or methods.
• Uncertainty- An estimate of how far away an experimental result might be from the true value. It includes both random and systematic errors.
• Hazard- A chemical or piece of apparatus that could cause harm. It is expected that in risk assessments the nature of the hazard is also specified. For example `Hydrogen peroxide is an irritant`
• Risk- A step in the method involving a hazard that may result in danger. For example `Hydrogen peroxide could get into the skin when pouring it into the measuring cylinder`
• Control Measures- Something that can be done to reduce or prevent a risk, while still allowing you to carry out the experiment. For example `Wash hands immediately when in contact with hydrogen peroxide`
• Hypothesis- An educated prediction. As the {independent variable} increases, the {dependent variable} increases/decreases.
• Inaccuracy- Something within the method which means the results aren't as close as they should be to the true value
• Control experiment- To find out whether the results you collected were caused by the independent variable being altered, or some other factor.
• To control the temperature you could use a thermostatically controlled water bath
• A great resolution improves precision, as the repeat readings are more close together/ similar
• To improve the inaccuracy of counting bubbles of gas, use a gas syringe
• To more accurately measure a moving object, use light gates or record using slow motion on a camera.
• To improve the accuracy of using a manual thermometer, use a digital thermometer.
• To be more confident in results, you can use a larger sample size, or a larger number of participants.
• Physics graphs- The line should touch one of the axis, usually directly proportional or at a constant rate.
• Chemistry graphs- Should go to 0, could be at a decreasing rate or at an increasing rate.
• Biology- no line of best fit, join up the crosses. Could be at an increasing or at a decreasing rate.