Sample exam questions - air and water - OCR 21st CenturyMaths questions

Understanding how to approach exam questions helps to boost exam performance. Question types will include multiple choice, structured, mathematical and practical questions.

Part ofChemistry (Single Science)Air and water

Maths questions

Maths questions will appear throughout both exam papers, and at both Foundation tier and Higher tier.

Don't forget to take a ruler and calculator into the exam.

Maths questions often start with the command word 'Calculate', followed by a blank space for your working. It is important that you show your working - don't just write the answer down. You might earn marks for your working even if you get the answer wrong.

Always include the correct units for your answer, unless they are already given on the answer line. This may earn you an additional mark.

Check carefully to see if the question tells you to round your answer to a particular number of significant figures or decimal places. Don't forget to check your rounding.

Other command words you might see in maths questions include:

  • 'predict' - look at some data and suggest an outcome - don't just guess, look at trends in the data and use your scientific knowledge and understanding to make a sensible suggestion
  • 'estimate' - suggest a rough value without doing a calculation - don't just guess, use your scientific knowledge and understanding to make a sensible suggestion
  • 'show' -write down the details, steps or calculations to prove that an answer is correct

Maths questions might include tables and graphs as well as calculations. When drawing a graph, make sure you:

  • put the independent variable (the factor you changed) on the x-axis
  • put the dependent variable (the factor you measured) on the y-axis
  • construct regular scales for the axes
  • label each axis with the quantity and units, eg time (s)
  • plot each point accurately
  • decide whether the origin (0,0) should be used as a data point
  • draw a straight or curved line of best fit if appropriate.

These questions have been written by Bitesize consultants as suggestions to the types of questions that may appear in an exam paper.

Learn maths skills with Dr Alex Lathbridge

Brush up on the maths you need for your exam - percentages, averages and converting units.

Open Transcript

Sample question 1 - Foundation

Question

What is the balanced chemical equation for the combustion of methane?

Put a tick (✔) in the box next to the correct statement. [1 mark]

ACH4 + O2 → CO2 + H2O
BCH4 + 2O2 → CO2 + H2O
CCH4 + 2O2 → CO2 + 2H2O
DCH4 + O2 → CO2 + 2H2O
A
CH4 + O2 → CO2 + H2O
B
CH4 + 2O2 → CO2 + H2O
C
CH4 + 2O2 → CO2 + 2H2O
D
CH4 + O2 → CO2 + 2H2O

Sample question 2 - Higher

Question

Propane burns in air to form carbon dioxide and water. The chemical equation for this reaction is:

C3H8 + 5O2 → 3CO2 + 4H2O

Use the bond energies in the table to calculate the energy required to break the bonds in the reactant molecules. Show your working. [1 mark]

BondBond energy
C-C348 kJ/mol
C-H412 kJ/mol
O=O498 kJ/mol
BondC-C
Bond energy348 kJ/mol
BondC-H
Bond energy412 kJ/mol
BondO=O
Bond energy498 kJ/mol

Sample question 3 - Higher

Question

Hydrogen reacts with bromine to form hydrogen bromide. The chemical equation for the reaction is:

H2 + Br2 → 2HBr

a) Use the bond energies below to calculate the energy change of the reaction between hydrogen and bromine. Show your working. [3 marks]

BondBond energy
H-H434 kJ/mol
Br-Br193 kJ/mol
H-Br366 kJ/mol
BondH-H
Bond energy434 kJ/mol
BondBr-Br
Bond energy193 kJ/mol
BondH-Br
Bond energy366 kJ/mol

b) Is the reaction exothermic or endothermic? [1 mark]

Next page
Practical questions
Previous page
Free response questions

More guides on this topic

Related links