Ice Cream Investigation

Learning Objectives (National Curriculum - Science, KS2)

• Working Scientifically:
  • Pupils should be taught to plan different types of scientific enquiries to answer questions, including recognising and controlling variables where necessary.
  • Pupils should ask relevant scientific questions and use different types of scientific enquiries to answer them.
  • Pupils should make systematic and careful observations and take accurate measurements using standard units, using a range of equipment.
• States of Matter (Y4 Programme of Study):
  • Observe that some materials change state when warmed or cooled, and measure temperature changes to explain these changes.

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Success Criteria

By the end of the lesson, pupils will be able to:

• Identify the scientific question: How does salt affect the freezing speed of ice cream?
• Recognise variables:
  • Independent variable: Presence of salt with ice.
  • Dependent variable: Time taken for mixture to freeze into ice cream.
  • Controlled variables: Amount of ice, amount of salt, quantity of ice cream mixture, shaking time and method, bag types.
• Plan a simple investigation: Understand the procedure and safety measures.
• Observe and record: Measure and compare times or observe the consistency and texture of the ice cream.
• Draw conclusions: Explain why salt affects the freezing time using scientific reasoning linked to freezing points.

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Equipment and Preparation

• Prepare enough materials for 6 groups (5 pupils/group) to ensure active hands-on engagement:
  • 2 large zip-lock bags per group
  • 2 small zip-lock bags per group
  • Ice cubes (class supply)
  • Table salt – measured 6 tbsp per group in small containers for cleanliness
  • Ice cream mixture pre-prepared (milk, sugar, vanilla) in separate containers
  • Timers or stopwatches (one per group or use a classroom timer)
  • Gloves or towels (hand protection)
• Label each large bag clearly before distribution.
• Ensure a classroom setup where groups can work without interfering with each other.
• Display a large visual diagram illustrating variables and the setup as a reference.

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Lesson Structure (60 minutes)

Introduction (10 minutes)

1. Engage:

   • Show a ready-made ice cream sample made with salt and ice, then one made without salt – ask: Which do you think took longer to make? Why?
   • Introduce the scientific question: "How quick does the ice cream freeze using salt and ice compared to ice only?"

2. Recap:

   • Briefly remind what variables are: independent, dependent, controlled.
   • Ask pupils to predict what happens when salt is added to ice and why.

Main Activity (40 minutes)

1. Setup & Hypothesis (10 minutes):

   • Each group labels their large bags "Ice only" and "Ice + Salt".
   • Measure and pour ice cream mixture into two small zip-lock bags, seal air out carefully.
   • Add ice cubes to large bags, add salt to one, insert small bags accordingly.

2. Investigation (15 minutes):

   • Put on gloves/towels.
   • Shake both large bags gently but continuously.
   • Start timers simultaneously.
   • Observe and record: time taken for mixture to become ice cream; note texture and temperature if desired.
   • Encourage pupils to note any differences between the two bags.

3. Data Recording & Group Discussion (15 minutes):

   • Record findings on printed worksheets or science journals (time, texture description).
   • Encourage pupils to discuss: Did salt make the ice cream freeze faster? Why?
   • Recap role of salt lowering the freezing point of ice (linked to their scientific knowledge on states of matter and temperature changes).

Plenary (10 minutes)

• Groups share their observations and compare results.
• Teacher leads class discussion on:
  • The importance of controlling variables (e.g., same amount of ice cream mixture, same shaking time).
  • What could we change next time? (e.g., different amounts of salt, different shaking speeds, different mixtures).
• Summarise key learning about planning investigations and understanding how variables affect outcomes in scientific questions.

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Assessment Opportunities

• Formative: Teacher observation during group discussions to check understanding of variables and the scientific method.
• Written: Completed worksheet or journal entry explaining:
  • The question being investigated.
  • Identification of variables.
  • Prediction/hypothesis.
  • Results and conclusion.
• Peer assessment: Groups compare findings and discuss discrepancies or confirmation of predictions.
• Oral: Pupils articulate reasons for salt affecting freezing using scientific vocabulary ('freezing point', 'temperature', 'states of matter').

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Differentiation and Extension

• For SEN or lower ability students:
  • Scaffold worksheet with sentence starters: "I think the salt will...", "The variable I changed was...", "The results were..."
  • Provide adults or peers for support during experiment.
• For more able pupils:
  • Challenge to design a follow-up experiment changing another variable (e.g., quantity of salt or time shaken).
  • Investigate the molecular reason why salt lowers freezing point (collaborate in pairs with additional reading or videos).

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Cross-Curricular Links

• Maths: Measuring time, comparing quantities, recording data in tables.
• English: Scientific writing – recording observations, using precise vocabulary.
• PSHE: Working cooperatively in groups, sharing equipment safely.

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Resources for Teacher

• Pre-prepared bags of ice cream mixture and salt to maintain timing.
• Clear safety instructions emphasising the cold temperature and use of gloves/towels.
• Large class display of variable types and experiment process to reinforce learning visually.

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This lesson seamlessly integrates hands-on enquiry with scientific thinking, meets National Curriculum requirements for Year 4 science investigation skills, and inspires curiosity about everyday science phenomena in a fun, memorable way.