Maths Flashcards
To calculate rate of reaction from a graph, if the graph is a straight line
rate = change in y-axis /
change in x-axis
To calculate rate of reaction from a graph if the graph is a curve
- Draw a tangent to the curve at point where you are being asked to calculate the rate
- Rate = change in y-axis (of the tangent) /
change in x-axis
Equation of a straight line graph (linear relationship)
y = mx + c
- m = gradient, c = y-intercept
To calculate percentage difference:
% difference = final value - initial value
initial value
Why are percentages (or percentage increase/decrease) often used instead of absolute numbers?
- Valid comparisons can be made
- From groups/control of different sizes
Define uncertainty
The amount of error your measurements might contain
To calculate the absolute uncertainty of a piece of apparatus
± smallest reading on the apparatus / 2
- e.g. a thermometer gives readings to the nearest 1°C
- The real temperature could be up to 0.5°C smaller or larger
- Uncertainty value of ± 0.5°C
To calculate the percentage uncertainty
Percentage error = (uncertainty value / your measurement) x 100
- e.g. a reading of 45°C was taken from a thermometer with 1°C increments
- % uncertainty = (0.5 ÷ 45) x 100 = 1.1%
Circumference of a circle
2 π r
Area of a circle
π x r2
Volume of a cylinder
π x r2 x h
To determine an ‘appropriate’ number of significant figures:
Use the same number of significant figures as the least accurate measurement
Am I looking at frequencies, and whether my observations differ from expected values?
For example – count the number of red, purple and white flowers that come from a genetic cross of two purple flowers where I expect a ratio of 1:2:1
Test – chi squared test
Am I looking at the relationship between two variables?
For example – ice-cream consumption and blood sugar levels, to see if people who eat a lot of ice-cream have higher blood sugar.
Test – Spearman’s rank correlation
Am I looking at the whether there is a difference in the means between two separate/independent groups?
Test – Student’s t-test/ unpaired t-test
