Get your students excited and engaged in learning about the risks of pollution to the world’s oceans with this fun and easy prac for World Oceans Day on Wednesday 8 June. If you're already using Edrolo Year 7 Science you can access a full risk assessment for this practical through Risk Assess. Otherwise access it here.

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Fun fact to get students curious‍

Oceans absorb 30-50% of the world's CO₂. When CO₂ is dissolved into water, it forms a solution called carbonic acid. This acid increases the acidity of the ocean. 
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‍Lesson Outcomes

Students will

• understand that acidification of the ocean affects coral.
• be able to explain the relationship between CO₂ and the level of acid in the ocean.

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‍Prior Knowledge

Where does CO₂ come from? 

• Discuss natural sources of CO₂ such as animal respiration.
• Discuss human-made sources of CO₂ such as burning of fossil fuels like petrol in the car or coal generating electricity.

What does a high or low concentration of acid mean?

Form a hypothesis on how an increase in acidity can affect coral.

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Teacher-led activity 

Ask students to form a hypothesis on how an increase in acidity can affect coral.

Coral has a hard exoskeleton made from calcium carbonate, the same thing that makes up egg shells. Increasing the acidity can reduce coral's ability to grow, and can even cause the calcium carbonate to break down. 

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Materials

3 x test tubes 

1 x test tube rack 

1 x 10 ml measuring cylinder 

3 x medium size calcium carbonate chips (marble chips)

3 x different concentrations of HCl, 0.5M, 1.0M, 2.0M

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Method

1. Place one marble chip into each test tube.  

2. Place 2 mL into the first test tube. 

3. Observe how quickly the reaction is occurring.

4. Repeat steps 2-3 for the other HCl concentrations. 

Based on the results of this experiment, if the acidity of the ocean increases, how might this affect the coral?

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‍Student-led

Check out the curriculum mindmap and ask students to investigate the questions related to what you are currently covering in class.

‍Extension

Try different concentrations of other types of acid - do they have the same effect? Are they faster or slower acting?

Research the different shapes of coral - how would the different surface areas increase or decrease the speed of the reaction with acid?

‍Curriculum MindMap

Did you know? Every practical in our new Year 7 Science print textbook and digital resource has a complete risk assessment available through Risk Assess. Find out more about our new Year 7 Science resource.