These eight questions cover the four lessons in measurement and chemical investigation. Try each one on paper first.
Questions
Question 1. A burette starts at 2.30 mL and ends at 27.15 mL. Calculate the volume delivered. [2 marks]
Answer
27.15 − 2.30 = 24.85 mL, written to two decimal places.
Question 2. A 100 mL measuring cylinder has 1 mL divisions, and the meniscus sits exactly on 64 mL. How should the reading be written? [1 mark]
Answer
64.0 mL, to one decimal place, because the reading is taken to half a division.
Question 3. A student compares the time for 1 g of zinc to react with 50 mL of acid at 25 °C and 45 °C. State the manipulated and responding variables. [2 marks]
Answer
Manipulated: temperature of the acid. Responding: time taken for the zinc to react.
Question 4. In Question 3, name two fixed variables and explain why one of them must be fixed. [3 marks]
Answer
Mass of zinc and concentration of acid (volume of acid also works). The mass of zinc must be fixed because a larger mass takes longer to react, which would change the time and make the comparison unfair.
Question 5. Copper(II) carbonate powder is added to dilute sulfuric acid. Write one observation and one inference. [2 marks]
Answer
Observation: the green powder dissolves, colourless bubbles form and the solution turns blue.
Inference: carbon dioxide is released, and copper(II) sulfate solution is formed.
Question 6. Decide whether each statement is an observation or an inference: (a) the test tube becomes hot, (b) the reaction is exothermic, (c) a brown gas forms. [3 marks]
Answer
(a) Observation, because it is felt or measured. (b) Inference, because it explains the heat as energy released. (c) Observation, because the colour is seen.
Question 7. Write a hypothesis for an experiment where the concentration of sodium thiosulfate is changed and the time for a cross to disappear is measured. [2 marks]
Answer
The higher the concentration of sodium thiosulfate, the shorter the time for the cross to disappear. The hypothesis names both the manipulated and responding variables and states the direction.
Question 8. Plan a fair test to find out whether stirring affects how fast sugar dissolves in water. Include variables, method idea and conclusion. [6 marks]
Answer
Aim: to investigate whether stirring speeds up dissolving.
Variables: manipulated is stirring or no stirring, responding is the time for all the sugar to dissolve, fixed are the mass of sugar, volume and temperature of water, and type of container.
Method: put 5 g of sugar into 100 mL of water at room temperature in two beakers. Stir one at a steady rate and leave the other still. Record the time until no solid remains. Repeat each twice.
Conclusion: if the stirred sample dissolves in a shorter average time, then stirring speeds up dissolving.
If you got these wrong
Questions 1 and 2 use reading apparatus and measurement precision. Questions 3, 4 and 7 use identifying variables in a chemical investigation.
Questions 5 and 6 use writing observations separately from inferences. Question 8 uses planning a fair comparison.
To build a timed mixed set, use the timed original practice session builder. For help with written plans, see online one-to-one Chemistry tuition.