Breaking Down Food

Overview

Duration: 45 minutes
Class size: 90 students (split into 3 groups of 30)
Unit: Digestive System Discoveries (Lesson 3 of 6)
National Curriculum link:

• Science, Key Stage 2 (Years 3 & 4)
• Pupils should be taught to:
  • describe the simple functions of the basic parts of the digestive system in humans
  • identify the different types of teeth in humans and their simple functions
  • construct and interpret a variety of food chains, identifying producers, predators and prey (Relevant to digestion context)
• Programme of Study reference: Biology – Animals, including humans

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Learning Objectives

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

• Describe the role of the stomach in digestion with a focus on chemical digestion (NC link: KS2 Science – describe functions of the digestive system).
• Explain how gastric juices help break down food using age-appropriate scientific vocabulary (enzymes, acid, digestion).
• Use a model to demonstrate the process of chemical digestion in the stomach.
• Work collaboratively to visualise and communicate scientific processes effectively.

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Resources

• Large classroom model of the digestive system (highlighting the stomach)
• Gelatine cubes (to represent protein food)
• Clear plastic containers labelled “Stomach”
• Vinegar solution (to mimic gastric acid)
• Paper clips or small items to simulate "enzymes" that help break down gelatine
• Whiteboards and markers for group work and quick quizzes
• Worksheet summarising the stomach’s role and key terms
• Projector/interactive whiteboard for images and animations
• “Digestive system discovery journal” for each pupil to note observations

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Lesson Structure

1. Starter Activity (5 minutes)

• Quick recap: Use interactive questioning to remind pupils of previous lessons (focus briefly on the digestive system parts and mechanical digestion).
• Learning Intentions: Share and display the objectives for today’s lesson, explaining that the focus is on how the stomach breaks down food chemically.

2. Introduction (7 minutes)

• Show a diagram and use the large classroom stomach model to explain where the stomach sits in the digestive system.
• Introduce the concept of chemical digestion: emphasise that the stomach uses gastric juices (acid + enzymes) to break down food.
• Use simple terms: stomach acid (vinegar as analogy), enzymes (paper clips simulate chewing or cutting protein).
• Show a short animation or diagram illustrating the process of food turning into chyme within the stomach.

3. Main Activity: Hands-on Investigation (20 minutes)

• Divide the class into their three groups (30 pupils each), rotating through three stations if possible.
• Station 1: Model demonstration
  • Teacher or TA shows the gelatine cube in the “stomach” container filled with vinegar.
  • Pupils observe how the gelatine starts to break down (approximately 10 minutes).
  • Discussion of what is happening (chemical digestion by acid).
• Station 2: Enzyme simulation
  • Pupils use paper clips to “cut” pieces off paper or model proteins to simulate enzymes breaking down food molecules.
  • Discussion on how enzymes speed up digestion inside the stomach.
• Station 3: Visualisation and Recording
  • Pupils use whiteboards to draw the stomach and the digestion process they observed.
  • Complete a short worksheet summarising the stomach’s role and the meaning of acid and enzymes.

4. Plenary (8 minutes)

• Class discussion where groups share what they learned using scientific vocabulary.
• Quick quiz using whiteboards: True/False or multiple choice on the role of the stomach and chemical digestion.
• Recap key vocabulary: stomach, gastric juice, acid, enzyme, chemical digestion, chyme.

5. Assessment & Feedback (5 minutes)

• Collect worksheets and review understanding of the stomach’s role.
• Formative assessment: Teacher notes observations on participation, use of vocabulary, and engagement.
• Address any misconceptions during plenary.

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Differentiation

• Lower ability: Provide word banks and scaffold the worksheet with sentence starters. More teacher support during activities.
• Higher ability: Challenge pupils to explain why the stomach acid doesn’t digest the stomach itself (introduction to the concept of mucus lining).
• Use peer support and mixed-ability grouping to support pupils where necessary.

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Curriculum Links and Competency Development

National Curriculum Ref.	Lesson Coverage	Competencies Developed
Biology – Animals Including Humans	Description of the stomach and chemical digestion	Scientific vocabulary, observation skills
Working Scientifically	Use of models, conducting simple investigations	Hypothesising, data recording, teamwork
Speaking & Listening	Group discussions, sharing ideas and findings	Oral communication, confidence
Literacy (Science)	Writing and interpreting scientific terms	Reading comprehension, written expression

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Teacher Notes & Tips

• Ensure safety with vinegar and handling materials.
• Use animated storytelling to personalise the stomach as a “busy kitchen” breaking down food.
• Encourage pupils to make links to their own eating experiences.
• Use questioning to push thinking: “What do you think would happen if the stomach had no acid?”
• To manage a large class, employ support staff for the stations or run activities in rotation over 2 or 3 lesson segments if needed.

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This lesson blends practical investigation and visual modelling to embed deeper understanding of chemical digestion in the stomach, meeting KS2 curriculum standards while engaging large classes effectively.