Density Hotel Demonstration
Grade: 10
Subject: Physical Sciences
Term: 1
CAPS Type: Extension Activity / Informal Investigation
Topic: Density, Relative Density, Floating and Sinking
Aim
To investigate relative density using layered liquids and different floating or sinking objects.
Learning Outcome
- Explain relative density.
- Observe how liquids form layers according to density.
- Predict whether objects will float or sink.
- Compare the density of different substances.
- Explain why objects settle at different layers.
Time Allocation
Approximately 30 to 45 minutes.
How Does It Work?
Density is the amount of mass packed into a certain volume.
Substances with a higher density sink below substances with a lower density.
Liquids with different densities can form layers.
Objects placed into the layered liquids will float or sink until they reach a layer with a similar density.
Scientific Background
Density is calculated using:
Density = Mass ÷ Volume
Objects and liquids with higher density sink, while objects and liquids with lower density float.
Water has a density of approximately 1 g/cm³.
Objects less dense than water float. Objects more dense than water sink.
Most Dense
Maple syrup forms the bottom layer.
Middle Density
Water forms the middle layer.
Least Dense
Oil forms the top layer.
Hypothesis
If liquids with different densities are added carefully into a container, then they will form layers from most dense to least dense.
Objects placed into the container will settle at different layers depending on their density.
Variables
Independent Variable
Type of liquid or object used.
Dependent Variable
Position of the object in the density column.
Control Variables
- Same container.
- Same liquid quantities.
- Same room conditions.
- Same procedure when adding liquids.
Apparatus
- Tall glass, measuring cylinder or clear container
- Maple syrup
- Water
- Food colouring
- Cooking oil
- Coin
- Grape
- Plastic bottle cap
- Ping pong ball
- Spoon or pipette, optional
Safety Precautions
- Handle glass containers carefully.
- Clean spills immediately.
- Do not drink any liquids used in the experiment.
- Wash hands after the activity.
- Keep the work area clean and dry.
Prediction Activity
Before starting the investigation, predict where each object will settle.
| Object | Prediction |
|---|---|
| Coin | |
| Grape | |
| Bottle Cap | |
| Ping Pong Ball |
Method
Part A: Building the Relative Density Column
- Pour maple syrup into the bottom of the container.
- Add enough syrup to form the first layer.
- Add a few drops of food colouring to the water.
- Slowly pour the coloured water into the container.
- Pour carefully so the water forms a separate layer above the syrup.
- Slowly pour cooking oil on top.
- Observe the layers formed in the container.
Part B: Testing the Objects
- Carefully place the coin into the container.
- Observe where it settles.
- Repeat with the grape.
- Repeat with the bottle cap.
- Repeat with the ping pong ball.
- Record all observations.
Results Table
| Object | Observation | Final Position |
|---|---|---|
| Coin | ||
| Grape | ||
| Bottle Cap | ||
| Ping Pong Ball |
What Learners Should Observe
- Syrup forms the bottom layer.
- Water forms the middle layer.
- Oil forms the top layer.
- The coin sinks to the bottom.
- The grape settles between layers.
- The bottle cap floats above the water layer.
- The ping pong ball floats on the top layer.
Different objects settle at different levels because they have different densities.
Explanation of Results
Coin
The coin is more dense than all the liquids and sinks to the bottom.
Grape
The grape is more dense than water but less dense than syrup, so it floats on the syrup layer.
Bottle Cap
The bottle cap is more dense than oil but less dense than water, so it floats on the water layer.
Ping Pong Ball
The ping pong ball is less dense than all the liquids and floats at the top.
Conclusion
Liquids and objects arrange themselves according to density.
More dense substances sink below less dense substances.
Objects float when they are less dense than the liquid below them.
Important Note
Density affects whether substances float, sink or settle between layers.
Heavy objects are not always more dense.
A large object may still float if its density is low.
Expected Results
- Clear liquid layers.
- Objects floating at different heights.
- Floating and sinking based on relative density.
- Separation between liquids due to density differences.
Questions for Learners
- What is density?
- Which liquid was the most dense?
- Which liquid was the least dense?
- Why did the syrup stay at the bottom?
- Why did the oil float on top?
- Why did the coin sink to the bottom?
- Why did the grape stop above the syrup?
- Why did the ping pong ball float at the top?
- What does relative density mean?
- Why do some objects float while others sink?
Common Mistakes
- Pouring liquids too quickly and mixing the layers.
- Using a container that is too small.
- Dropping objects too forcefully.
- Confusing mass with density.
- Assuming heavier objects are always more dense.
- Not allowing the liquids to settle properly.
Teacher Notes
- This investigation works best in a tall clear container.
- Encourage learners to predict outcomes before testing.
- Food colouring improves visibility of the water layer.
- Learners should observe carefully before discussing density calculations.
- This activity works well as a demonstration or group practical.
Teacher Tip
Pour liquids slowly over the back of a spoon to reduce mixing and create clearer layers.
Extension Activity
Ask learners to test additional objects such as:
- Tomato
- Marble
- Plastic toy
- Rubber stopper
- Berry
- Small metal object
Learners can predict where each object will settle before testing.
Real-World Application
Density is important in ships and submarines, oil spills, hot air balloons, ocean currents, material identification, engineering and food production.
Understanding density helps explain why substances float, sink or separate into layers.