1. Cell sizes Cells are often too small to be seen with the naked eye
Cell lengths are measured in µm (micrometres). A micrometre is 1000th of a millimetre.
Write this in standard form.

2. Answer
1µm = 1 x 10-3mm
Or 1 x 10-6m

3. What is the difference between….
A hypothesis
and
A prediction?

4. Answer
A hypothesis is an idea that explains how or why something happens
A prediction is a statement that suggests what YOU think will happen (usually based on your scientific knowledge)

5. Presenting data
List three features of a good table

6. A good table
Values of the independent variable appear in the first column
Headings contain units
Units are not included in the body of the table
Measurements are recorded to an appropriate and consistent number of decimal places
Measurements are made in a logical and sequential order

7. How long will headstones made from different rocks last?
This study used different rocks and looked at the effect of acid on the rock.
The idea was that acid rain wears away rocks over time.
To make the study manageable a stronger acid was used over a shorter time period.
The mass of the rock was measured, before and after soaking the rock in acid
What is the independent variable?
What is the dependent variable?
Suggest two control variables

8. Answers: Independent – type of rock Dependent – mass loss
Control – type of acid; concentration of acid; length of time; size of rock; temperature of acid; amount of acid

9. Resolution
I always use the same balance to weigh the samples. The balance can weigh to 1 dp (0.1g).
The first sample weighed 45.9g at the start and 44.9g at the end – what is the mass loss?

10. Mass loss
45.9 – 44.9 = 1.0g
Why do we state the mass loss as 1.0g not 1g?

11. Practicals you need to know

12. Chemistry

13. Physics

14. What do you need to know? Describe the method Identify variables
Suggest tables to record data
Identify errors in a given method OR suggest improvements (Evaluate)
Process data (provided): e.g. calculate means; plot graphs
Describe what the results (given) show
What you DON’T need to do – remember your results!
You may also be asked about similar experiments

15. MWB terms quiz Write the meanings of the following terms: 1. Precision
2. Accuracy
3. Anomaly
4. Fair test
5. Repeatable
6. Resolution
7. Validity
8. Categoric variable

16. MWB terms answers
1. Precision – measurements where there is little spread about the mean value
2. Accuracy – closeness to true value
3. Anomaly – data values which fall outside of the variation caused by random uncertainty
4. Fair test – one in which only the independent variable affects the dependent one
5. Repeatable – same person doing the experiment again gets the same results
6. Resolution – the smallest change in the quantity being measured that an instrument can determine
7. Validity – suitability of the procedure to answer the question being asked
8. Categoric variable – one that is described by a name rather than a number