Edexcel IGCSE Chemistry Observations and Variables

Practise Edexcel IGCSE Chemistry observations, measurements and variables by using colour, effervescence, gas collection and controlled variables.

Exam points

Use observations such as colour, bubbles or gas syringe movement to judge a reaction.
State controlled variables such as concentration, volume, mass, surface area or temperature.

Covered syllabus points

Precise observations and measurements Independent, dependent and control variables

[Maximum number: 1]

A student uses this apparatus to investigate the rate of reaction between dilute sulfuric acid and an excess of small pieces of zinc.

Figure for Question Observations, measurements and variables question 1 — Edexcel IGCSE Chemistry

This is the student's method.
Step 1 use $50 \mathrm{~cm}^{3}$ of dilute sulfuric acid
Step 2 add approximately 5 g of small zinc pieces to the sulfuric acid
Step 3 quickly connect the gas syringe
Step 4 record the reading on the gas syringe every 30 seconds until the reaction stops

State how the student would know when the reaction stops.

[Maximum number: 2]

A student investigates the effect of temperature on the rate of reaction between two solutions, A and B . When the reaction occurs, the mixture turns from colourless to blue.

This is the student's method.
- pour $25 \mathrm{~cm}^{3}$ of solution A into a conical flask
- add solution B and measure the temperature of the mixture
- record the time taken for the mixture to turn blue

The student repeats this method at different temperatures.

Give two variables that the student needs to keep constant in this investigation.

1

2

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Covered syllabus points

Observations, measurements and variables question 1

Observations, measurements and variables question 2