Gases In The Atomsphere

Question 1

The proportions of gases in atmosphere

Answer 1

78% nitrogen, 21% oxygen, nearly 1% argon and only 0.04%

Question 2

Investigating proportion of oxygen in air (iron)

Answer 2

1. Soak iron wool in ethanoic acid. Then push the wool into a measuring cylinder and invert the measuring cylinder
2. Record the starting position of the water using the scale on the measuring cylinder - this is the starting volume of air
3. Over time, the level in the cylinder rises because the iron reacts with the oxygen to make iron oxide. The water rises to fill the space the oxygen took up
4. Leave the measuring cylinder until the water level stops changing
5. Record the finishing position of the water - this is the final volume of air

Question 3

Investigating the proportion of oxygen in the air (phosphorus)

Answer 3

1. Place phosphorus in a tube and attach a glass syringe at either end. One filled with air, on empty
2. Heat the phosphorus and use the syringes to pass air over it, making phosphorus oxide
3. As it reacts, the amount of air in the syringes decreases
4. Measure the starting and final volumes of the air using the scale on the syringes
5. Calculate percentage of oxygen in air by using start volume - final volume / start volume x 100

Question 4

Describe the combustion of magnesium in air

Answer 4

Burns with a bright white flame in air and the white powder formed is magnesium oxide. Magnesium oxide is slightly alkaline when dissolved in water

Question 5

Describe the combustion of hydrogen in air

Answer 5

Burns very easily in oxygen, has an orangey/yellow flame and the only product is water. Often used as a test for hydrogen (squeaky pop)

Question 6

Describe the combustion of sulfur in air

Answer 6

Pale blue flame and produces sulfur dioxide. Sulfur dioxide is acidic when dissolved in water

Question 7

Describe the formation of carbon dioxide from thermal decomposition of metal carbonates

Answer 7

1. If you heat metal carbonate, you get carbon dioxide and metal oxide
2. This is an example of thermal decomposition
3. Copper (II) carbonate is a green powder that will easily decompose to form carbon dioxide and copper (II) oxide (black) when heated
4. Heat this in a test tube, add a delivery tube and collect in a gas syringe

Question 8

What is the greenhouse effect?

Answer 8

Atmospheric gases e.g. carbon dioxide, methane and water vapour naturally act as an insulting layer. They absorb most of the air that would normally be radiated out into space and re-radiate it towards earth. If these gases increase too much, then the average temperature on earth will increase