Question 1: Explain in your own words what is meant by 'oxygen evolution' in the context of Earth's atmosphere.

Answer: Oxygen evolution refers to the process by which oxygen is produced and released into Earth's atmosphere, primarily through photosynthesis by plants and algae.

Question 1: What are the main organisms responsible for oxygen production in Earth's early atmosphere?

Answer: Photosynthetic organisms such as cyanobacteria and algae.

Question 2: Describe the basic mechanism of photosynthesis related to oxygen evolution.

Answer: Photosynthesis is a process where plants, algae, and certain bacteria convert sunlight, carbon dioxide, and water into glucose and oxygen. During this process, the splitting of water molecules releases oxygen as a byproduct.

Question 1: If a certain amount of water undergoes photosynthesis and produces 12 grams of oxygen in one hour, how many moles of oxygen is this? (Molar mass of O₂ = 32 g/mol)

Answer: 0.375 moles

Question 2: Calculate the volume of oxygen (at standard temperature and pressure) produced if 0.375 moles are generated. (Use 1 mole of gas = 22.4 L)

Answer: 8.4 liters

Question 1: Describe a simple experiment to demonstrate oxygen production from aquatic plants. Include variables to control and safety precautions.

Answer: Place aquatic plants in water under sunlight in a test tube or container. Control variables include light intensity and water purity. Safety precautions involve handling water safely and avoiding direct contact with chemicals used in related experiments.

Question 1: Scientists have found that oxygen levels in the atmosphere increased significantly approximately 2.4 billion years ago. What natural process is most likely responsible for this change?

Answer: The increase was mainly due to photosynthesis by early cyanobacteria, which produced large amounts of oxygen as a byproduct.

Question 2: Based on data showing a gradual rise in oxygen levels over millions of years, explain how photosynthesis contributed to this change.

Answer: Photosynthesis by evolving organisms converted carbon dioxide and water into glucose and oxygen. Over time, the accumulation of oxygen in the atmosphere led to the development of more complex life forms and an oxygen-rich environment.

Question 1: Explain how the process of photosynthesis leads to oxygen evolution and why this was crucial for the development of life on Earth. (6 marks)

Answer: Photosynthesis involves the conversion of sunlight, carbon dioxide, and water into glucose and oxygen, with the release of oxygen as a byproduct. This process was crucial because it increased oxygen levels in the atmosphere, enabling the evolution of aerobic organisms and complex life forms.

Question 1: Describe one modern technological application that relies on oxygen evolution or photosynthesis principles.

Answer: Artificial photosynthesis systems that produce hydrogen or oxygen fuel using sunlight and water.