Gases in the atmosphere

Question 1

What are the approximate %s of each gas in the air?

Answer 1

• 78% nitrogen
• 21% oxygen
• Small amounts of other gases (e.g. noble gases, carbon dioxide and water vapour

Question 2

How do u determine volume of oxygen in an experiment?

Answer 2

-Subtract the final volume from the initial volume to determine the volume of oxygen.
Divide this value by the initial volume and multiply by 100 to calculate the percentage of oxygen in the air

Question 3

Steps for finding % of oxygen in the air. (8)

Answer 3

1. Place wet iron filings inside an inverted burette
2. Place the open end of the burette in a trough of water
3. Open the tap to let water enter the burette
4. Close the tap. Record the volume of gas in the burette
5. Leave until the volume of gas inside remains constant
6. Record the final volume of gas
7. Subtract the final volume from the initial volume
8. Divide this by the initial volume and multiply by 100

Question 4

How does magnesium react w oxygen when burned?

Answer 4

-Burns with a very bright, white flame

Question 5

How does sulfur react w oxygen when burned?

Answer 5

-Burns with a blue coloured flame, producing a colourless gas

Question 6

How does hydrogen react w oxygen when burned?

Answer 6

-Burns quickly, producing a loud squeaky pop

Question 7

What does copper carbonate break down into whilst heated and what is this reaction called?

Answer 7

• Copper carbonate → copper oxide + carbon dioxide

- thermal decomposition reaction

Question 8

How can you tell a reaction has taken place when copper carbonate is heated?

Answer 8

-can see a colour change from green to black during the reaction

Question 9

How do you test for CO2?

Answer 9

• Take an aqueous solution of limewater (calcium hydroxide) and bubble through the gas.
• If the gas is carbon dioxide, the limewater solution will turn from clear to cloudy

Question 10

How does the greenhouse effect work?

Answer 10

• sun emits short wavelength infrared towards earth
• earth absorbs a portion, longer wavelength reflected
• greenhouse gases can absorb the reflected radiation
• greenhouse gases re-radiate it and some heats the earth

Question 11

Why is it important to maintain satisfactory levels of greenhouse gases on earth?

Answer 11

• Without greenhouse gases, temperatures would be too low to support life.
• However, high concentrations of greenhouse gases cause temperatures to rise too high, which also threatens life on Earth