Gases in the atmosphere

What are the 4 most abundant gases in the atmosphere?

nitrogen → 78%

oxygen → 21%

argon → 0.9%

carbon dioxide → 0.04%

Describe an experiment to calculate the % of oxygen in the air

1. a pile of copper powder is placed in a glass tube connected to 2 gas syringes with one end containing 100cm³ of air and the other containing 0cm³

2. the joints on the apparatus are checked & sealed to avoid any other air from entering the experiment

3. the copper is heated with a Bunsen burner & the gas syringes slowly passes air to one another

4. the copper turns black as it has reacted with the oxygen to form copper II oxide

5. the % of oxygen in the air can be calculated by subtracting the intial volume of air (100cm³) by the final volume of air

What is combustion?

- a reaction where a substance burns in oxygen

- the substance gains oxygen so it is an oxidation

What happens in the combustion of magnesium, hydrogen & sulfur?

MAGNESIUM → 2Mg + O₂ → 2MgO

HYDROGEN → 2H₂ + O₂ → 2H₂O

SULFUR → S + O₂ → SO₂

What is thermal decomposition?

a reaction where a substance is broken down using heat energy

What happens when a metal carbonate undergoes thermal decomposition?

metal carbonate → metal oxide + carbon dioxide

(e.g. CuCO₃ → CuO + CO₂)

What are some greenhouse gases?

- carbon dioxide (CO₂)

- methane (CH₂)

- water vapour

What is the greenhouse gas effect?

• When energy from the sun travels to the Earth as short wavelength radiation, the surface of the Earth then radiates the energy as long wavelength radiation.

• Some of the long wavelength radiation interacts with the greenhouse gases in the atmosphere

• Because the energy is trapped in the atmosphere, this causes the temperature of the atmosphere to increase

• Leading to global warming