Lesson 7: Choice Cooling

 Preparation

Equipment

• Water
• Freezer
• sugar
• flavouring
• ice
• salt
• small ziplock bags
• large ziplock bags

 Lesson Plan

Tuning In

• Display the Chemical Sciences: Clever Changes – Teaching Presentation. Read over the learning objective on Slide 50.
• Read through Slides 51 to 55. Encourage student engagement by using the question prompts in the presentation.
• Watch the video Chemical Sciences: Clever Changes – Cool to observe examples of materials reacting to being cooled. Before proceeding to the question-and-answer part of the video, discuss what students observed and answer any questions. You may want to watch this part more than once. Afterwards, play through the question-and-answer part of the video, pausing after each question to allow students to contribute answers.

Teacher Instruction

• Display an A3 version of the Predict and Prove – Template to the class.
• Ask students to sit in a circle on the mat. Discuss what liquids are and what happens when liquids are cooled.
• Pass around bags containing the liquid ice-cream mixture and ask students what they think is in it. After students observe and discuss, explain that the mixture contains milk, sugar and flavouring.
• Ask students what they think will happen if they put one of the liquid bags into a freezer. Write the students’ predictions in the, ‘What I think will happen…’ section of the Predict and Prove – Template. Then, put one of the ice-cream mixes into a freezer and leave it there for at least two hours.

Guided/Independent Learning

• Discuss the procedure for making ice-cream in a bag, without the spoiler that ice-cream is the end result. Ask students to predict what will happen after they shake the mixture in ice for 5 to 10 minutes. Ask them whether they think anything will be different between the mixture in the freezer and the mixture in the bag of ice. Add students’ answers to the Predict and Prove – Template.
• Instruct students to stand in a circle. Distribute the remaining batches of the ice-cream mix evenly among the students. At different points of the circle, ask students to shake vigorously, softly, or in different ways. For example, “Shake it while standing on one leg. Shake it above your head. Shake it clockwise or anticlockwise.” Ask students to be careful how they grip the bags, so they do not accidentally break them. Double-bagging both bags, or using clear duct tape to reinforce them, may also prevent accidents.
• After 5 to 10 minutes, reveal the ice-cream. Spoon it into cups and give students time to eat it.

Wrapping Up

• Instruct students to return to the mat and sit in a circle. Reveal the effect cooling had on the milk mixture. Pass around the hardened, frozen version of the ice-cream. Discuss the outcome of both experiments and why one version was hard and the other was light and fluffy. Add the answers and discoveries to the Predict and Prove – Template. Discuss what you would do to reverse the changes and return the mix to its previous state. Once completed, add this poster to the unit display wall.
• Revise the facts about cooling and add any relevant new words to the Chemical Sciences: Physical Changes – Word Wall.

 Differentiation

Extending Students

• More-confident students can make their own ice-cream mixture by placing the ingredients into the ziplock bags themselves.
• More-confident students can independently write their own prediction and results on the Predict and Prove – Template.

Supporting Students

• If some students are allergic to the ingredients used in this lesson, plan substitute ingredients in advance.

 Assessment Strategies

Suggested Assessment Strategies

• used strategic whole class or individual questioning
• observed student participation during learning activities
• recorded student progress on a checklist
• annotated student work samples
• collected and reviewed student work samples
• facilitated whole class or peer feedback sessions
• encouraged student self-reflection
• administered formal assessment tasks.

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