Learning Objective

1. Learning Objective • To understand the requirements for the assessed practicals.

2. What do I have to do? • The assessment is divided into two parts: • The practical task with associated questions where you may need to draw tables and/or graphs, make observations, draw conclusions and make evaluative comments. • The microscope task where you have to draw something, maybe measure something, identify things, discuss structural features etc…

3. Skills for observations… • You need to be careful that you are recording your observations in results tables and not your conclusions. • You need to read the practical protocol very carefully and completely before you start. • You need to be aware of what a control is and why it is used. • You will be assessed (by us) on your practical techniques including safety.

4. Drawing tables • Draw a table to show the observations from the experiment below: D 0% glucose C 5% glucose A 20% glucose B 10% glucose

5. Your table... Did you: • Record the colour change rather than the final colour? • Give your table a title? • Rule up your table? Had there been units, where would you have put them?

6. Tables – some key points Students often: • Put units in the body of the table • Leave out units all together • Do not identify the independent variable by putting it in the first column • Do not ‘rule up’ tables Doing/Not doing these things will cost you marks!

7. Observations – some key points Students often: • Put ‘clear’ when they mean ‘colourless’ • Record conclusions rather than observations • Record final colour when asked to record colour change • Draw theoretical diagrams rather than what they can actually see • Do not record a difference in reaction – simply whether or not a reaction has occurred.

8. Draw graphs for the following data sets

9. Checking your graphs Do your graphs have: • Labelled axes? • Units? • Titles? • Do they go through the origin? Should they? • Do they have a line of best fit? What does it look like? • Have you drawn your axes correctly? • Have you got your variables on the correct axis?

10. Graphs – some key points Students often: • Draw the wrong type of graph • Use inappropriate scales • Put the axes the wrong way round • Do not label axes • Do not give units (or give incorrect ones) • Draw incorrect trend lines

11. Some very important words You must understand the key terms: • Accuracy • Anomalous • Reliability • Precision • Validity

12. Accuracy • Students will be expected to appreciate that they accuracy of an observation, reading or measurement is an indication of how close it comes to the ‘true’ value or outcome. • This could refer to: • closeness of data points to a line of best fit • Accuracy of measuring apparatus by % error

13. Anomalous • Students will be expected to appreciate that an individual result or piece of data may not always match the trend shown by other results. • If this result, after repeats, still appears to be ‘odd’ then it will be considered to be anomalous.

14. Reliability • Students will be expected to apreciate that a result or data may not always match the trend shown by other results. • The reliability of this data can be measured by carrying out repeats and/or statistical tests (such as the mean or standard deviation) • If, for example, the ‘odd’ result is confirmed to be sound by repeats, then it is not anomalous

15. Precision • Students will be expected to appreciate that measurements or observations can vary in how exact, definite, clearly stated or able to be reproduced they are • It could also refer to the number of decimal places that a number is expressed in.

16. Validity • Students will be expected to appreciate that results, measurements or procedures will vary to the extent that they actually measure or carry out what they are designed to do. • Inappropriate measurements or procedures could lead to conclusions that are not valid because they have not done what they set out to do.