Investigating respiration
Respiration by living organisms can be investigated by carrying out experiments to show the production of carbon dioxide and heat.
Limewater can be used to detect carbon dioxide.
If carbon dioxide is bubbled through Calcium hydroxide solution. It turns milky in the presence of carbon dioxide. then it turns from clear to cloudy/milky in colour. This is why limewater used in a simple respirometer can show that more carbon dioxide is present in exhaled air compared to inhaled air.
Breathing in through the mouthpiece draws air from the atmosphere in through tube A. Breathing out through the mouthpiece bubbles exhaled air through tube B. After a few breaths the limewater in tube B will turn cloudy as the exhaled air contains more carbon dioxide.
Question
If inhaled air contains 0.04% carbon dioxide and exhaled air 4%, how many times more carbon dioxide do you breathe out than you breathe in?
100 times more.
Investigating heat production
The release of heat can be shown by carrying out an experiment using When a seed sprouts a shoot and breaks dormancy. seeds. Two vacuum flasks are used.
Aerobic respiration is investigated through an experiment which looks at heat loss in germinating peas as they respire.