Lung Gas Exchange Worksheet

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Part 1: Learn About Diffusion

WALT: We Are Learning To explain how oxygen and carbon dioxide move between the alveoli and the blood.

Success criteria: I can define diffusion. I can describe the direction of oxygen and carbon dioxide movement. I can use concentration data to explain gas exchange.

Diffusion is the net movement of particles or gases from an area of high concentration to an area of low concentration. Diffusion is a passive movement, so it does not require energy from the cell.

Gas exchange happens in tiny air sacs called alveoli. Oxygen diffuses from the air in the alveoli into the blood because the oxygen concentration is higher in the alveoli. Carbon dioxide diffuses from the blood into the alveoli because the carbon dioxide concentration is higher in the blood.

Dyslexia-friendly reading option: Read one short paragraph at a time. Use a coloured overlay or ruler to track each line, and ask for the text to be read aloud if helpful.

Approximate Gas Percentages

Inhaled air: Oxygen 21% | Carbon dioxide 0.04% | Nitrogen approximately 79%

Exhaled air: Oxygen 16% | Carbon dioxide 4% | Nitrogen approximately 79%

1. Which statement best defines diffusion?

The movement of particles from low concentration to high concentration

The net movement of particles from high concentration to low concentration

The movement of blood around the body

2. Is diffusion an active or passive movement? Explain what this means.

3. Complete the labels using these words: alveoli, blood, oxygen, carbon dioxide.

Air sacs where gas exchange occurs: ____________________

Gas moving from the alveoli into the blood: ____________________

Gas moving from the blood into the alveoli: ____________________

Liquid tissue that carries gases around the body: ____________________

Part 2: Apply Your Understanding

4. Fill in the blanks.

Oxygen diffuses from the ____________________ into the ____________________ because its concentration is higher in the alveoli.

Carbon dioxide diffuses from the ____________________ into the ____________________ because its concentration is higher in the blood.

5. Explain the concentration gradient for oxygen at the alveoli. Include the words high concentration, low concentration, and diffuses.

6. Explain the concentration gradient for carbon dioxide at the alveoli. Include the words blood, alveoli, and diffuses.

7. Use the data to complete the comparisons.

Inhaled air contains ________% oxygen. Exhaled air contains ________% oxygen.

Oxygen decreases by approximately ________ percentage points as air passes through the lungs.

Carbon dioxide increases from ________% in inhaled air to ________% in exhaled air.

8. What do the changes in oxygen and carbon dioxide percentages show about gas exchange?

9. Choose all statements that are correct.

Oxygen moves from the alveoli into the blood.

Carbon dioxide moves from the blood into the alveoli.

Diffusion requires energy from the cell.

Nitrogen is approximately 79% in both inhaled and exhaled air.

10. Exit ticket: In one or two sentences, explain how diffusion helps keep the blood supplied with oxygen and removes carbon dioxide.

Answer Key and Learning Support

1. The net movement of particles from an area of high concentration to an area of low concentration.

2. Passive movement. It does not require energy from the cell.

3. Alveoli; oxygen; carbon dioxide; blood.

4. Alveoli; blood; blood; alveoli.

5. Oxygen concentration is high in the alveoli and lower in the blood, so oxygen diffuses into the blood.

6. Carbon dioxide concentration is high in the blood and lower in the alveoli, so carbon dioxide diffuses from the blood into the alveoli.

7. 21%; 16%; 5 percentage points; 0.04%; 4%.

8. Oxygen is taken into the blood, while carbon dioxide is removed from the blood and breathed out.

9. Oxygen moves from the alveoli into the blood; carbon dioxide moves from the blood into the alveoli; nitrogen is approximately 79% in both.

10. Answers should mention oxygen diffusing into the blood and carbon dioxide diffusing out of the blood into the alveoli.

Differentiation Strategies

Use a word bank containing: alveoli, blood, oxygen, carbon dioxide, high concentration, low concentration, diffusion, passive. Provide a partially completed sentence frame or allow students to explain answers orally. Pair students for the data questions and read the information aloud for learners who need support.

Extension Activities

Explain how thin alveolar walls, a large alveolar surface area, and a good blood supply help diffusion happen quickly. Research how exercise changes breathing rate and explain why the body needs faster gas exchange during exercise.

NZ Curriculum link: Year 9 Science, Te Mātaiaho: human transport systems and the movement of substances, including diffusion and the movement of gases in and out of the blood.