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# 7.1 Composition of Air * Nitrogen: 78% * Oxygen: 21% * CO2: 0.04% * Noble gases: 0.9% * Water vapor/other gases ## Tests for Gases **Test for Oxygen:** * Supports burning * Re-lights glowing splint **Test for CO2:** * Supports burning/Denser than air * Turns hydrocarbonate indicator red → ye...

# 7.1 Composition of Air * Nitrogen: 78% * Oxygen: 21% * CO2: 0.04% * Noble gases: 0.9% * Water vapor/other gases ## Tests for Gases **Test for Oxygen:** * Supports burning * Re-lights glowing splint **Test for CO2:** * Supports burning/Denser than air * Turns hydrocarbonate indicator red → yellow * Lime water: colorless → milky # 7.2 Photosynthesis * Light energy absorbed by chlorophyll * CO₂ + water = food (glucose) * Chemical energy in food * Oxygen by product * **Equation:** 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂ (carbon dioxide + water → glucose + oxygen) **Testing for Starch:** * Boil leaf * Destroy cell membranes * Leaf in hot alcohol * Dissolve chlorophyll * Wash leaf * Add iodine * Test for starch # 7.3 Respiration * Food (glucose) + oxygen → carbon dioxide + water * **Equation:** C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O * Respiration = breathing * Involves a series of controlled chemical reactions * Respiration in cells * During, chemical stored in food (glucose) * Other useful support body * Oxygen needed, CO2/Water produced # 7.4 Hydrogen Carbonate Indicator * Indicates changes in CO₂ levels * Purple → red → Yellow # 7.5 Exhaled Air Composition * Exhaled air: More water vapor, more CO₂, less oxygen * Temperature increases # 7.6 Respiration and Photosynthesis * Respiration/photosynthesis balance CO₂/O₂ in nature * Human activities (burning fossil fuels/clearing forests) disrupt the balance * Increase in CO₂ leads to the greenhouse effect/global warming * Side effects: Living things in Polar regions lose habitat/die, Flooding of low-lying areas, Unusual weather patterns (typhoons/heat waves/droughts) # 7.7 Air Pollutants and Their Effects * Sulphur dioxide, nitrogen oxides, ozone, carbon monoxide, suspended particulates * Irritation to the eyes * Headache * Irritation to the throat/airways * AQHI * Tells the public about the possible health risks caused by air pollutants * Advises on precautionary measures **Additional Notes:** * Gas exchange: The movement of gases in and out of the body's systems **Image Description:** The image is a handwritten note with various chemical formulas and diagrams. The notes appear to be science lecture notes, or study guide notes of a biology topic. It shows different tests on different gases and topics on respiration, photosynthesis, and gas exchange in the body. It also shows different equations and chemical reactions.