The percentage of oxygen in the air

Which gas is the most abundant in the earth's atmosphere?

• Nitrogen

• Oxygen

• Carbon dioxide

• Helium

What is the approximate percentage of oxygen in the earth's atmosphere?

• 10%

• 15%

• 20%

• 25%

What is the effect of oxygen on a glowing splint?

• Oxygen extinguishes a glowing splint

• Oxygen makes a glowing splint relight

• Oxygen extinguishes a glowing splint with a pop sound

• Oxygen does not have any effect on a glowing splint

Which of these gases has a variable percentage in the air?

• Nitrogen

• Oxygen

• Carbon dioxide

• Water vapour

The percentage of oxygen in the atmosphere is 20%.

How many cm3 of oxygen would you find in 50 cm3 of air?

• 5 cm3

• 10 cm3

• 15 cm3

• 20 cm3

In the experiment shown above, when should we stop passing the air in the syringe back and forth over the heated copper?

• When all the copper turns black

• When the volume of air in the syringes stops changing and remains constant

• When the copper glows inside the tube

• We just pass it 6 times back and forth

What type of reaction is occurring?

• Thermal decomposition

• Oxidation

• Dissolving

• Reduction

Why is the air passed over the copper several times whilst heating?

• To ensure that all the oxygen has been removed

• To keep the copper cool during the experiment

• To allow the copper to burn

• To stop the copper from reacting.

What is formed when copper reacts with oxygen?

• carbon dioxide and water

• carbon dioxide

• copper (II) oxide

• copper dioxide

What colour is copper(II) oxide?

• White

• Orange/brown

• Blue

• Black