1. Plants release oxygen into the atmosphere - Edexcel - GCSE Chemistry - Question 1 - 2019 - Paper 1

Since the atmosphere contains 21% oxygen, the bar chart should indicate that 21% of the chart is allocated to oxygen.

To find the volume of oxygen in 300 cm³ of air, we use the fact that 21% of air is oxygen. Therefore, the volume of oxygen would be:
$ext{Volume of oxygen} = 300 ext{ cm}^3 imes 0.21 = 63 ext{ cm}^3$

The lines would be drawn as follows:

• Atomic number → Number of protons
• Mass number → Total number of protons and neutrons

The correct test that shows a gas is oxygen is:
2. A glowing splint will relight when placed in the gas.