Cellular RespirationInvestigations

Junior Science

Lesson Objectives

• Know the composition of air and percentages of each gas in the Air both inhaled and exhaled

• Carry out simple experiments to investigation which demonstrates qualitatively and Quantatively the effect of respiration on air composition.

• Review experimental practices– Know what is meant by Qualitative data.

– Write relevant and conclusive evaluations and summaries.

How does respiration affect the composition of air that is

inhaled and exhaled?

Air Composition and Respiration

To carry out a qualitative analysis to see the difference between inhaled and exhaled air

Glucose + Oxygen Carbon Dioxide + Water + Energy

Qualitative data is data that is non-numerical in nature and is collected through methods of observations.

What we know…

What we need to know….

How do we test for Carbon Dioxide????

Normal Air contains 0.04% Carbon Dioxide

Lime Water – CO2 Test

• Lime water or Calcium Hydroxide - Ca(OH)2 is used to test for the presence of Carbon Dioxide.

• It is a clear solution which turns milky white in the presence of CO2

• The calcium hydroxide reacts with Carbon Dioxide to form insoluble Calcium Carbonate.

• Lime water + carbon dioxide → Chalk + water

Ca(OH)2 + CO2 → CaCO3 + H2O

Particles ofCalcium carbonate are suspended in the Lime water

As pressure decreasesCO2 from the air is drawn

through the lime water and reacts with it.

Air from LungsA B

Atmospheric Air

CO2 (0.04%) Breathing

OUT

CO2 from the lungs bubbles

through the lime water and reacts with it

CO2 (4%)

Investigation Set-up

Breathing

IN

What’s Happening

• The calcium hydroxide reacts with carbon dioxide in both boiling tubes to form insoluble Calcium Carbonate.

Lime water + Carbon dioxide → Calcium Carbonate + water

• The boiling tube containing the exhaled air turns milky white much quicker that the boiling tube receiving inhaled air.

• This shows that exhaled air contains more carbon dioxide that inhaled air.

Respiration and Peas

What do you thing will happen?

ScenarioFresh and boiled pea seeds

were place in two Thermos

Flasks.

Thermometers were placed

in each flask and they were

sealed with wet cotton wool

and left for a day?

What Happens….

• As the peas in A begin to germinate they will release energy through respiration

• The temperature reading on the thermometer will go up as respiration is an exothermic chemical reaction

• In B there will be no change as the peas have been boiled (are nor longer living) and therefore no longer able to germinate and release energy

Respiration and Woodlice

What do you thing will happen?

Woodlice

Soda Lime (CaOH/NaOH)

The ScenarioSome woodlice are placed in boiling tube with someSoda Lime (Calcium Hydroxide and

Sodium hydroxide)

The system is closed with a fixed amount of air.The coloured liquid indicated the volume of air at 55ml.They are left in here for 1 week.

Air Volume (55ml)

What Happens…

• Soda lime, solid is generally a white to grayish white coloured solid. It is the mixture of calcium hydroxide and sodium or potassium hydroxide. It removes Carbon Dioxide from the Air.

• As the woodlice respire and use up the Oxygen the bubble of coloured liquid would move relative to the amount of oxygen used by the woodlice.

• The volume of Air in the tube should decrease.