Liquid Density Experiment

Year Level

Year 3

Duration

45 minutes

Class Size

6 students

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Curriculum Links

Australian Curriculum Version 9 — Science

• AC9S3U04: Investigate the observable properties of solids and liquids and how adding or removing heat energy leads to a change of state.
• AC9S3I04: Construct and use representations, including tables, simple column graphs and visual or physical models, to organise data and information, show simple relationships and identify patterns.
• AC9S3I06: Write and create texts to communicate findings and ideas for identified purposes and audiences, using scientific vocabulary and digital tools as appropriate.
• AC9S3I05: Compare findings with those of others, consider if investigations were fair, identify questions for further investigation and draw conclusions.

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Learning Objectives

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

• Describe liquid density as a property that can explain why some liquids float on others.
• Predict and observe the behaviour of different liquids when combined based on density.
• Conduct a hands-on "lava oil" experiment to visually explore liquid density and immiscibility.
• Record observations systematically using diagrams and simple tables.
• Communicate their findings using appropriate scientific vocabulary.

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Key Vocabulary

• Density
• Liquid
• Float
• Sink
• Layers
• Observation
• Experiment
• Hypothesis

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Materials Required

• Clear plastic or glass beakers (at least one per pair)
• Water
• Cooking oil (vegetable or mineral oil)
• Food colouring (various colours)
• Small fizzing tablets (e.g., effervescent vitamin C or Alka-Seltzer)
• Plastic droppers or spoons
• Paper towels or cloth for spills
• Science journals or worksheets for observation notes

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Safety Considerations

• Food-grade materials only.
• No ingestion of materials.
• Use wipes or paper towels to clean spills immediately to avoid slips.
• Handle fizzing tablets carefully and with teacher supervision.

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Lesson Sequence

1. Introduction to Liquid Density (10 minutes)

• Begin with a guided discussion to activate prior knowledge: “What do you think makes some liquids float on top of others?”
• Explain in simple terms: Density is how heavy something is for its size. Liquids with lower density float on liquids with higher density.
• Show an example: Pour a small amount of oil into water and demonstrate how the oil floats on water—ask students why this might happen.
• Introduce the key vocabulary words.

Curriculum link: This ties to properties of liquids and solids (AC9S3U04).

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2. Predict and Plan (5 minutes)

• In pairs, students predict what will happen when food colouring and fizzing tablets are added to a mixture of water and oil.
• Encourage students to record their predictions in their science journals or worksheet, using drawings or simple sentences.
• Teacher writes the word "Hypothesis" on the board and explains it is their best scientific guess.

Curriculum link: Posing investigable questions and making predictions (aligned with AC9S3I01).

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3. Lava Oil Experiment (20 minutes)

• Each pair fills a beaker about two-thirds with water.
• Add drops of food colouring (choose any colour) to the water—observe how it dissolves.
• Slowly pour oil into the beaker until almost full—observe how oil forms a layer on top.
• Drop one piece of fizzing tablet into the beaker and watch the 'lava lamp' bubbles form as coloured water droplets move through the oil.
• Students observe and sketch the layers and bubbles in their journals.
• Teacher facilitates discussion about why the oil and water don’t mix and why the bubbles move the way they do.

Curriculum link: Investigating observable properties, recording observations with diagrams (AC9S3I04, AC9S3I06).

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4. Sharing and Reflecting (7 minutes)

• Invite pairs to share observations and explain what they saw.
• Discuss if their predictions were correct and why.
• Encourage students to use scientific vocabulary during their explanations.
• Highlight the importance of careful observation and communication in science.

Curriculum link: Compare findings, draw conclusions, and identify further questions (AC9S3I05).

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5. Wrap-up and Extension (3 minutes)

• Summarise key points about liquid density and why some liquids float on others.
• Optionally, prompt students to think of other liquids or situations where density could be important (e.g. why oil spills float on water).
• Suggest at-home activity: Try layering other liquids like honey or syrup with water and observe.

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Assessment Strategies

• Formative assessment through observation of student engagement and use of vocabulary during discussions.
• Review students’ science journals/worksheets for accuracy in drawings and explanations of the experiment.
• Questioning to elicit understanding of liquid density concepts and processes.

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Teacher Notes and Tips

• Keep explanations simple and use visuals—children at Year 3 grasp concepts better with concrete examples.
• Encourage curiosity by allowing students to ask questions and hypothesise freely.
• Manage materials carefully to avoid spills.
• This lesson can integrate digital tools if available, such as recording videos of the experiment to replay and discuss.

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This lesson plan is designed with the Australian Curriculum v9 Year 3 Science standards in mind, specifically addressing properties of liquids and investigative skills, while making science engaging through a hands-on demonstration that connects directly to real-world observations of liquids and density.