Handouts are available below.

Big Idea

Getting better at CER is all about finding ways to practice it in the lab. Today, I’m showing a quick demo you can do with your students that gets them to practice CER while answering this question: do hot lemons release more juice than cold lemons? All that’s needed is a couple of lemons, a microwave, a knife, a juicer (or a couple of beakers) and a graduated cylinder. 

Episode Notes

Do hot lemons release more juice than cold lemons? Here’s how we put this to the test in class.

• Get two lemons of roughly the same size and cool them for the same amount of time in the fridge – for about four hours to get them really cold.
• Take them out of the fridge, cut one in half, juice each half, and pour the contents into a graduated cylinder for measurement. The best method would be to use a juicer, but if you don’t have one, I recommend using a fork and juicing into a large beaker to capture most of the juice and then to strain out any seeds while pouring into the graduated cylinder.
• Then, put the 2nd lemon into a microwave and heat for approximately 25 seconds. Get the lemon really warm, but try not to overheat because water will escape the lemon when it gets too hot.

After all the juicing, look at the results together and have students write a CER statement by giving them a template.

• First, the claim, which I tell students to say “Hot lemons release more, less, or the same amount of juice than cold lemons”.
• Next, for evidence, I get students to start by saying, “According to my data, x milliliters of juice was released from cold lemons while hot lemons released y milliliters of juice”.
• Finally, for reasoning, I get students to say, “this increase or decrease in juice is because… <and provide reasoning.” I get students to write their statements, and then we share. During sharing, I ask students to compare CER statements and determine which statements written by students were strong and what made them strong.

Resources

Handout(s): Ep77 Handouts – Do Hot Lemons Release More Juice? (CER Practice)

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