Laboratory work 3: Observing chest movement during breathing
In the first work the chest circumference is measured with a tape: at rest, after a deep inhalation and after a deep exhalation; the differences show chest mobility. The number of calm breaths per minute is also counted while seated (measure over clothes, with respect and in pairs; do not judge each other). In the second work the presence of carbon dioxide in exhaled air is shown: the student blows through a personal straw or tube (clean, own) into a test tube of limewater prepared by the teacher, and the water turns cloudy because carbon dioxide reacts with calcium hydroxide forming calcium carbonate. With distilled water there is no change. Safety: do not drink limewater and do not suck through the tube – only blow; if it touches skin, rinse with plenty of water; if it gets into the eyes, rinse at once with clean running water for 15 minutes and tell the teacher. Conclusion: chest volume changes with breathing; exhaled air contains carbon dioxide.
Write your results in a table (rest, deep inhale, deep exhale) and calculate the difference. Do not compete with others – everyone’s measurements differ.