INVESTIGATING RESPIRATION WITH LIMEWATER
Objectives:
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Observe the reaction between carbon dioxide and lime water
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To investigate how exhaled air differs from inhaled air in terms of carbon dioxide
content.
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To compare the time taken for inhaled and exhaled air to turn cloudy
Prediction:
1. What do you think will happen when exhaled air is bubbled through limewater?
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The limewater will turn cloudy.
2. What do you think will happen when inhaled air is bubbled through limewater?
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The limewater remains clear.
Materials:
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Limewater (10ml per test tube)
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Test tubes – 2
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Straw
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Syringe
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Timer
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Measuring cylinder
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Beaker
Variables:
Independent Variable (what we are changing): type of air (inhaled & exhaled)
Dependent Variable (what we are measuring): time taken for limewater to turn cloudy
Control Variable (what stays the same): amount of lime water
Procedure:
1. Fill two test tubes with 10ml of lime water.
2. Use a syringe to collect air from the room and bubble it through the limewater in the
first test tube.
3. Use a timer to time how long it takes to turn cloudy.
4. Take a deep breath and blow gently through a straw into the second test tube.
5. Use a timer to time how long it takes to turn cloudy.
6. Write down your results and compare the two tests.
Observation:
Test
What happened to the limewater?
Time taken to turn cloudy
Inhaled air
Remains clear
x (because it did not turn
cloudy)
Exhaled air
Turned cloudy
– sec
Results & Analysis:
1. What do you notice about the limewater in the two tests? Explain why this happens.
●
Limewater turns cloudy in exhaled air, because exhaled air has a higher
concentration of carbon dioxide.
2. In every investigation, we need a control. What is the control in this investigation?
●
The test tube for inhaled air. This is because it remains clear, which allows us
to compare between exhaled and inhaled air.