AQA Science B Controlled AssessmentLearning Objective: Revise the key areas included in the Science controlled assessment unit
Guide to the CASection Marks Awarded Slide Pictogram1: Research 42: Planning 83: Managing and Assessing 8Risk4: Collecting Data 85: Processing Data 106: Analysing Data 67: Evaluating the Practical 6ActivityTotal 48
Starter: Match the Keywords Aim How will you carry out your experiment?Dependent Variable What are you trying to find out? Method What are you deliberately changing in your experiment? Control variable What equipment will you use?Independent Variable What are you going to measure? Prediction What variables will you keep the same? Based on scientific knowledge what do you think the Apparatus relationship is between the dependent and Independent variables
Constructing Aims The purpose of my experiment is to investigate…………………................................... Writing Frame (a statement discussing the effect of the independent variable on the dependent variable)To gain the full marks in this area you must mention both the independent and dependantvariables i.e. Aim: To measure the effect of changing the temperature on the rate of a chemical reaction by timing how long it takes the cross to disappear with different temperatures of Sodium thiosulphate are reacted with hydrochloric acid .
Methods BAD GOODI filled half of the crucible 1. Half fill the crucible withwith alcohol. Then I put alcohol.50ml of water in the beaker 2. Put 50ml of water in theand measure the beaker and measure thetemperature. I then set up temperature.the equipment as shown in 3. Set up the equipment asthe diagram and put my shown in the diagram.goggles on. I lit the alcoholand burned for 5 mins. I 4. Put your goggles on.measured the temperature 5. Light the alcohol and burnand recorded it in the table. for 5 minutes 6. Measure the temperature and record in the table. Think of your method as a recipe. It should be a set of clear steps in a PASSIVE VOICE.
Identifying Variables1. Finding the effect of string length on the time of pendulum swing.2. Finding how the number of coils affects the number of clips that the electromagnet can pick up.3. Measuring the temperature of water as it is being heated.4. Investigating the effect of different types of exercise on pulse rate.5. Investigating the effect of Caffeine on a persons reaction time Identify the INDEPENDENT, DEPENDANT and 2 possible CONTROL variables for each experiment
Predictions: Describing relationships As ……… (independent) increases/decreases Writing Frame: ……… will increases/decrease (dependent) because………………….. (scientific knowledge)To gain the full marks in this area you must link the independent and dependant variables and use information from your research to support your “educated guess” i.e. Aim: to measure the temperature of water as it is being heated. Prediction: As the time the beaker is over the Bunsen increases the temperature of the water will increase until the temperature of the water reaches 100oC as this is the boiling point of water. Initially the temperature will increase because as the water particles are heated they vibrate faster, their kinetic energy is transferred into heat energy. However once their boiling point is reached they have enough kinetic energy to change state from liquid to a gas, so steam will be produced.
Managing and Assessing RiskPlace all of your apparatus in Equipment/Ch Hazard Risk Control emical Measuretable and use your ownknowledge and HAZCARDS to Magnesium Irritant: Can Medium as it Clear up sulphate damage skin can be spilt spillagescomplete (0.1M) cause slips easy and immediately or falls if looks like using paper Apparatus (Equipment) spilt water so you towels. Wash Magnesium sulphate (0.1M) might forget hands after to wash it off practical, Zinc sulphate (0.1M) wear goggles Test tube rack Zinc sulphate 4 test tubes (0.1M) measuring cylinder Spatula Carrying out Electronic balance the experiment Look at the full example Tin that your teacher shows Iron Glassware you. Electronic balance Don’t forget to record the Tin sources that you use Iron
Drawing Tables Independent Dependant Variable (Units) Variable (Units) 1 2 3 Mean Exclude any anomalous repeats when All data to 2 Decimal Points calculating the mean. Make sure you show which ones have been excluded.This is the standard table. You may need a slightly different one if you are not doing repeats
Bar Charts – Categoric Data Title Graph showing the mean reaction times of No marks 4 students Straight lines for but 5 plotting essential 4 Dependant Variable e.g. Mean Reaction Time (s) 3 Key Correctly Reaction Timelabelled, appr 2 (s) opriately Even bars scaled Y axis 1 with units 0 Kate Mary Bob Peter Independent variable e.g. Pupil N.B. The title of the axes Correctly labelled appropriately scaled Are the same as the X axis with units Headings of the table!!
Line Graph – Continuous Data TitleNo marks Graph showing the mean temperature Clear Dependant Variable e.g. but change (oC) over 40s plotting Mean temperature (oC) 50essential 40 Key (if needed) 30 20 Column1 10 0 Line of best 10 20 30 40 fit Correctly labelled Independent Variable e.g. Time (s)appropriatelyscaled Y axis Correctly labelled, appropriately scaled X with units axis with units N.B. The title of the axes Are the same as the Headings of the table!!
Processing Data: Comment on the Graph Describe what your graph shows. Make a link between the independent and dependent variables. Does it match your prediction. Make direct reference to parts of your graph by quoting numbers/points from it. Increase DecreaseWriting Frame Directly proportionalKeywords: Linear Stays the same Double Halved
Analysing DataStep 1: What are the findings of your experiment? Use an ER statement i.e. Thesmaller the wood the quicker it burnsStep 2: Explain your ER Statement using information from your experiment to backit upStep 3: Compare your results to the results from the secondary data do theysupport/contradict your conclusion? How?Step 4: What are the limitations of your primary and secondary data? How couldyou overcome this?
EvaluationStep 1. Comment on the practical, was your method good? Did it enable you tocollect valid results? Did you have any anomalies? What did you do about it? Strengths WeaknessesStep 2. Evaluate your workingmethods. What were yourstrengths and weaknesses Improvements to be ReasonsStep 3. What improvements madecould you make and why wouldthis be of benefit?
Step 1Comment on I did lots of repeats to make sure that I couldreliability ignore any anomalous results Tips for your Evaluation The experiment was valid because there was only one independent variable, the pH and everythingComment on else, like the light and temperature was controlled.Validity and fairtesting I used the same number of seeds and volume of solution in each test so that it was fair. Step 2Improvement forgetting more data I only looked at the height of the cress seedlings. I could have measured the width and colour of the leaves as well.Improvement for The heights were all very small, so if I measuredgetting better them over a period of several weeks, I could see ifdata the pH affected the growth over a period of time. I could also have seen if pH slowed downImprovement for germination, rather than stopped it.greater accuracy I could have made it more accurate by using vernier calipers to measure the height of the seedlings.
Lastly: Quality of Written CommunicationLevel Key Points (get up to 6 extra marks)1 Knowledge of basic information Simple understanding Answer is poorly organised with few keywords . Spelling, punctuation and grammar is weak2 Knowledge of accurate information Clear understanding Answer has some structure, some keywords used but not always accurately. Spelling, punctuation and grammar is reasonably accurate.3 Knowledge of accurate contextualised information Detailed understanding supported by evidence Sequenced, structured and organised answer with appropriate use of keywords Spelling, punctuation and grammar is faultless