GCSE Science BUnit 4 (Using Practical and Investigative Skills)

This unit is assessed by Controlled Assessment. It is worth 25% of the total marks for the award and consists of one practical investigation based on themes from the specification. Centres will be able to choose one task from three options (one for each unit of content), which AQA will change each year. Tasks will be published on the AQA website one year before the date of submission (eg tasks published in 2011 may only be submitted for the 2012 examination). Guidance for teachers will be given with each investigation. Each task assesses How Science Works skills, and the candidate's ability to research an application of the science context. Methods and techniques used in the Controlled Assessment are not necessarily restricted to those mentioned in the specification.

Teachers are encouraged to undertake a wide range of practical and investigative work, including fieldwork, with their candidates. We share the view that it is not good practice to do practical work only for the Controlled Assessment. As teachers know well, candidates enjoy and are motivated by practical work. We have given many examples of practical work supporting the science content in Unit 1, Unit 2 and Unit 3. Full details of this practical work are included in our resources package.

Access arrangements (see sections 4.5 and 5.4) can enable candidates with special needs to undertake this assessment.

The right-hand column of the table below shows the Assessment Focus (AF) thread from National Strategies APP (Assessing Pupils'Progress). This will enable teachers to ensure progression from KS3 to KS4.

The Assessment Focus thread from National Strategies APP (Assessing Pupils' Progress) is shown next to each task. This will enable teachers to ensure progression from KS3 to KS4.

AF/thread 4/2a) stating the purpose of an investigation

Candidates should be able to:

• state the purpose of an investigation in terms of the possible relationship between two variables. These will usually be the independent and the dependent variables. Often there may be a quantitative relationship between these variables.

AF/thread 4/2b) recognise significant variables in an investigation

Additional guidance:

• The variables may be identified as continuous or categoric.

AF/thread 4/2c) recognising a control variable in an investigation

Candidates should be able to:

• identify variables that have been controlled, those that have not been controlled and those that cannot be controlled but should be monitored

d) understanding the purpose of a control group

Candidates should be able to:

• identify a control group that is being used, explain the benefit of using a control group and suggest how a control group could be set up. Examples may include the use of placebos in testing new drugs.

AF/thread 4/3e) identifying intervals in measurements.

Candidates should be able to:

• identify the interval between readings and suggest, with reason, a suitable interval for the independent variable.

AF/thread 1/3a) understanding the meaning of the term hypothesis

Candidates should understand:

• the difference between a hypothesis and a fact.

AF/thread 1/4b) being able to test a hypothesis

Additional guidance:

• Candidates should be able to plan a fair test to investigate a hypothesis

AF/thread 4/2c) planning a fair test.

Additional guidance:

• A fair test will normally involve changing one variable (the independent variable) to see what effect this has on another variable (the dependent variable) while keeping all other variables (control variables) constant.

AF/thread 5/1a) carrying out preliminary work

Additional guidance:

• Candidates should appreciate when a trial run would be appropriate and be able to suggest the values of the variables to be used in a trial run.

AF/thread 4/3b) understanding sample size

Additional guidance:

• Sample size is important and candidates should be able to suggest why a particular sample size is the most appropriate.

AF/thread 4/1c) using appropriate technology.

Additional guidance:

• Candidates should appreciate that technology such as data logging may provide a better means of obtaining data. They should be able to suggest appropriate technology for collecting data and explain why a particular technology is the most appropriate. Candidates should use ICT whenever appropriate.

AF/thread 4/4a) identifying some possible hazards in practical situations

Candidates:

• will be expected to independently recognise a range of familiar hazards and consult appropriate resources and expert advice

AF/thread 4/4b) suggest ways of managing risks.

Additional guidance:

• should assess risks to themselves and others and take action to reduce these risks by adapting their approaches to practical work in order to control risk.

AF/thread 4/3a) making simple observations from first hand evidence of an object or an event

b) carrying out practical work and research

AF/thread 4/1a) choosing the most appropriate equipment or technique for the task

AF/thread 4/1b)understanding why a particular technique or piece of equipment is the most suitable for the task

AF/thread 4/1c) knowing that a measuring instrument needs to be calibrated before use

Additional guidance:

• appreciate why a measuring instrument needs to be calibrated accurately and be able to describe how an instrument could be calibrated.

AF/thread 4/1d) understanding the meaning of the term resolution when applied to a measuring instrument.

Additional guidance:

• choose the correct scale to use for the intended measurement, and recognise whether the chosen instrument has the required resolution.

AF/thread 4/3a) appreciating that, unless certain variables are controlled, the results may not be valid

Candidates should be able to:

• explain whether results can be considered valid and recognise when an instrument or technique might not be measuring the variable intended.

AF/thread 4/3b) identifying when repeats are needed in order to improve reliability

Additional guidance:

• recognise that a second set of readings with another instrument or by a different observer could be used to cross check results.

AF/thread 4/3c) recognising the value of repeated readings to establish accuracy

Additional guidance:

• understand that accuracy is a measure of how close the measured value is to the true value.

AF/thread 4/3d) considering the resolution of the measuring device Resolution is the smallest change in the quantity being measured (input) of a measuring instrument that gives a perceptible change in the indication (output).

AF/thread 4/3e) considering the precision of the measured data Precision is indicated by the degree of scatter from the mean.

Additional guidance:

• distinguish between accuracy and precision when applied to an instrument's readings.

AF/thread 4/3f) identifying the range of the measured data.

Additional guidance:

• identify the upper and lower limits of the range and which extra results, within or outside the range, would be appropriate.

AF/thread 5/1a) appreciating when it is appropriate to calculate a mean

Candidates should be able to:

AF/thread 5/1b) calculating the mean of a set of at least three results.

Additional guidance:

• calculate the mean of a set of at least three results, recognising the need to exclude anomalies before calculating means to an appropriate number of decimal places.

AF/thread 3/2a) drawing tables

Candidates should be able to:

• draw up a table of two or more columns, with correct headings and units, adequately representing the data obtained.

AF/thread 3/2b) drawing charts and graphs

Additional guidance:

• construct an appropriate graphical representation of the data such as a bar chart or line graph and draw a line of best fit when appropriate. Candidates may use ICT to produce their graphs or charts.

AF/thread 3/1c) choosing the most appropriate form of presentation.

Additional guidance:

• identify the most appropriate method of display for any given set of data.

AF/thread 2/1a) recognising that an opinion might be influenced by factors other than scientific fact

Additional guidance:

• recognise that opinion may be influenced by economic, ethical, moral, social or cultural considerations.

AF/thread 1/2b) identifying scientific evidence that supports an opinion.

AF/thread 5/2a) identifying causes of variation in data

Candidates should be able to:

• identify from data whether there is any variation other than obvious anomalies, and identify a potential cause for variation or uncertainty

AF/thread 5/2b) recognising and identifying the cause of random errors

Candidates should be able to:

• appreciate that if a data set contains random errors repeating the readings and calculating a new mean can reduce their effect.
• appreciate that human error might be the cause of inaccurate measurement, and explain how human error might have influenced the accuracy of a measurement or might have introduced bias into a set of readings.

AF/thread 5/2c) recognising and identifying the cause of anomalous results

Candidates should be able to:

• identify anomalous results and suggest what should be done about them.

AF/thread 5/2d) recognising and identifying the cause of systematic errors.

Candidates should be able to:

• identify when a data set contains a systematic error and appreciate that repeat readings cannot reduce the effect of systematic errors.
• realise that a zero error is a type of systematic error. Candidates should be able to identify if a scale has been incorrectly used and suggest how to compensate for a zero error.

AF/thread 5/3a) describing the relationship between two variables.

Candidates should be able to:

• use terms such as linear or directly proportional, or describe a complex relationship.

AF/thread 5/3a) writing a conclusion, based on evidence that relates correctly to known facts

Candidates should be able to:

• state simply what the evidence shows to justify a conclusion, and recognise the limitations of the evidence.

AF/thread 5/3b) using secondary sources

Additional guidance:

• appreciate that secondary sources or alternative methods can increase reliability and validity.

AF/thread 5/4c) identifying extra evidence that is required for a conclusion to be made

Additional guidance:

• suggest that extra evidence might be required for a conclusion to be made, and be able to describe the extra evidence required.

AF/thread 5/4d) evaluating methods of data collection.

Additional guidance:

• appreciate that the evidence obtained may not allow the conclusion to be made with confidence. Candidates should be able to explain why the evidence obtained does not allow the conclusion to be made with confidence.