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Respirometer - Summer Theme 19

Major VersionM

by Procheta Mallik

Introduction

Chemical reactions often create a change in colour. Here, we use one such reaction to also measure our rate of respiration and metabolism

Video Overview

    • Do not ingest any material.

    • Do not suck from the straw by mistake; only blow, and blow gently!

    • Scissors/Cutters have sharp functional edges. Contact with body may harm.

  1. Make a mark on a fat straw at 1 cm from one end. Seal the end using a tape. Make sure the tape does not cross the 1 cm mark. Add another piece of tape to make a tight seal.
    • Make a mark on a fat straw at 1 cm from one end.

    • Seal the end using a tape. Make sure the tape does not cross the 1 cm mark.

    • Add another piece of tape to make a tight seal.

  2. Cut the straw at the 1 cm mark. This is our unit of measure. This piece can hold approximately 0.2 g of lime. Cut the straw at the 1 cm mark. This is our unit of measure. This piece can hold approximately 0.2 g of lime.
    • Cut the straw at the 1 cm mark. This is our unit of measure. This piece can hold approximately 0.2 g of lime.

  3. The given test tube has a capacity of about 17 ml. Add 6 test tubes full of water to a plastic bottle/container. This volume of water will be equal to approximately 100 ml.
    • The given test tube has a capacity of about 17 ml.

    • Add 6 test tubes full of water to a plastic bottle/container.

    • This volume of water will be equal to approximately 100 ml.

  4. Use the 100 ml of water we prepared in the previous step. Take one measure of 0.2 g of the calcium oxide (lime). Add it to the 100 ml of water and stir well.
    • Use the 100 ml of water we prepared in the previous step.

    • Take one measure of 0.2 g of the calcium oxide (lime).

    • Add it to the 100 ml of water and stir well.

  5. Remove the bottle cap and cut the bottle in half using a cutter/scissors. Place the upper half of the bottle inverted over the lower part. This acts like a funnel. Place a filter paper in the upper part of the bottle.
    • Remove the bottle cap and cut the bottle in half using a cutter/scissors.

    • Place the upper half of the bottle inverted over the lower part. This acts like a funnel.

    • Place a filter paper in the upper part of the bottle.

  6. Transfer the calcium hydroxide solution into the bottle through your bottle-funnel. Wait for all the liquid to filter down. Dip a red litmus paper into it and observe if there's a colour change.
    • Transfer the calcium hydroxide solution into the bottle through your bottle-funnel.

    • Wait for all the liquid to filter down.

    • Dip a red litmus paper into it and observe if there's a colour change.

  7. Transfer 5 ml of the filtered Calcium Hydroxide solution into a test tube with the help of a dropper. Add 5 drops of Bromothymol blue indicator. Insert a straw into the test tube and start to blow after taking a deep breath. Count and record the number of exhalations till the solution slowly turns pale green.
    • Transfer 5 ml of the filtered Calcium Hydroxide solution into a test tube with the help of a dropper.

    • Add 5 drops of Bromothymol blue indicator.

    • Insert a straw into the test tube and start to blow after taking a deep breath. Count and record the number of exhalations till the solution slowly turns pale green.

  8. Continue blowing till the colour of the liquid changes to a shade of green. Dip a red litmus paper into the solution and observe if the litmus paper changes its colour. Dip a red litmus paper into the solution and observe if the litmus paper changes its colour.
    • Continue blowing till the colour of the liquid changes to a shade of green.

    • Dip a red litmus paper into the solution and observe if the litmus paper changes its colour.

    • Patiently blow until the colour changes.

    • If it is taking too many blows it is also possible that, Lime is not mixed well with water.

    • If it is taking too many blows it is also possible that, not enough indicator is used.

  9. Run, jog or exercise to increase your rate of respiration. After physical exertion, try the same experiment again. Note down the number of exhalations required to change the colour to pale green.
    • Run, jog or exercise to increase your rate of respiration.

    • After physical exertion, try the same experiment again. Note down the number of exhalations required to change the colour to pale green.

    • Tabulate your observations in the given table.

    • Make sure to always use the same amount and concentration of the lime solution.

  10. Count the number of breaths required to change the colour of the solution to pale green. Record this in a table similar to that shown here.
    • Count the number of breaths required to change the colour of the solution to pale green.

    • Record this in a table similar to that shown here.

    • Repeat the experiment 5 times; the mean will give you a statistically better estimate of your rate of respiration.

    • Test the solution before exhaling and after, using red and blue litmus paper.

    • Add 3 to 5 drops of lime to the pale green solution. Predict, observe and record the colour change, if any.

  11. Change the volume of the solution and see how that affects the number of exhalations required to cause the colour change. Change the concentration of Calcium Hydroxide and see how that affects the number of exhalations required to cause the colour change. Try obtaining Carbondioxide from vinegar + Baking soda or Coke + Mentos and pass it through the respirometer  to observe the colour change.
    • Change the volume of the solution and see how that affects the number of exhalations required to cause the colour change.

    • Change the concentration of Calcium Hydroxide and see how that affects the number of exhalations required to cause the colour change.

    • Try obtaining Carbondioxide from vinegar + Baking soda or Coke + Mentos and pass it through the respirometer to observe the colour change.

  12. Perform the same experiment with dilute sodium hydroxide.
    • Perform the same experiment with dilute sodium hydroxide.

    • To learn variations of Respirometer. Please visit this link Respirometer (Variations).

Finish Line

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Vishal Bhatt

Member since: 04/26/2017

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