Experiments With Water — Class 5 EVS (CBSE)
Based on the NCERT Looking Around Grade 5 textbook. Explore what dissolves, floats, and sinks in water, then solve the practice set.
1. Why this chapter matters
Why does a nail sink but a ship float? Why does sugar vanish in tea but sand does not? This chapter answers these questions through simple experiments. Students learn about solubility — which substances dissolve in water — and about floating and sinking, which depends on density. The chapter also introduces the Dead Sea, where the high salt content makes people float easily. Hands-on experiments develop scientific thinking.
2. Solubility — what dissolves in water
Some substances dissolve in water, forming a solution. Others do not dissolve — they remain visible or settle at the bottom.
| Dissolves in water (soluble) | Does NOT dissolve (insoluble) |
|---|---|
| Salt | Sand |
| Sugar | Chalk powder |
| Lemon juice | Oil |
| Honey | Sawdust |
| Vinegar | Stones |
| Milk powder | Chilli powder |
Soluble substances mix completely with water and cannot be seen separately. Insoluble substances remain separate — they float, sink, or make the water cloudy.
Factors that affect dissolving
- Stirring: Stirring helps substances dissolve faster.
- Temperature: Hot water dissolves things faster than cold water.
- Amount: There is a limit to how much can dissolve (saturation point).
3. Floating and sinking
Whether an object floats or sinks depends on its density compared to water.
What is density?
Density is how much matter is packed into a given space. If an object is denser than water, it sinks. If it is less dense, it floats.
| Object | Float or sink? | Why? |
|---|---|---|
| Nail | Sinks | Metal is denser than water |
| Wood | Floats | Wood is less dense than water |
| Plastic bottle (empty) | Floats | Air makes it less dense |
| Plastic bottle (full) | Sinks | Water makes it denser |
| Coin | Sinks | Metal is denser than water |
| Cork | Floats | Cork is less dense than water |
| Ice cube | Floats | Ice is less dense than water |
Shape matters too
A ball of clay sinks, but the same clay shaped like a boat floats. This is because the boat shape displaces more water, making the overall density less than water.
Key idea: It is not just what something is made of — its shape also affects whether it floats.
4. The Dead Sea
The Dead Sea is a salt lake between Israel and Jordan. It is so salty that people float on its surface without any effort.
| Regular sea water | Dead Sea water |
|---|---|
| About 3-4% salt | About 30% salt (10x saltier) |
| Normal density | Very high density |
| Most objects sink | Most objects float |
The high salt content makes the water very dense. Objects (and people) float more easily in dense water.
5. Making a boat
Activity: Take a lump of clay. Drop it in water — it sinks. Now shape the same clay into a boat. Place it gently on water — it floats!
Why? In the boat shape, the clay pushes aside (displaces) more water. The water pushes back with an upward force. If the boat shape displaces enough water, it floats.
6. Activity corner
Activity 1: Take a glass of water. Try dissolving these one by one: salt, sugar, sand, chalk powder, oil. Stir each time. Write down which dissolve and which do not.
Activity 2: Collect 10 small objects (paper clip, eraser, coin, cork, leaf, plastic cap, etc.). Predict which will float and which will sink. Test each in a bucket of water. Record your results.
Activity 3: Make a boat from aluminium foil. See how many coins it can hold before sinking. Try changing the shape of the boat.
7. Common mistakes
- Mistake: Thinking 'dissolving' means the substance has disappeared forever Fix: The substance is still there — it has just mixed evenly with the water. You can get it back (for example, by evaporating the water).
- Mistake: Believing heavy objects always sink and light ones always float Fix: Floating depends on density, not just weight. A heavy ship floats while a small nail sinks.
- Mistake: Thinking the Dead Sea is called 'dead' because nothing lives in it Fix: Nothing can live in the Dead Sea because it is too salty. But the name also refers to its still, lifeless appearance.
8. Key facts
- Soluble substances dissolve in water (salt, sugar). Insoluble ones do not (sand, oil).
- Floating depends on density compared to water.
- Shape affects floating — a boat shape displaces more water.
- The Dead Sea is so salty that people float easily.
- Stirring and heat help substances dissolve faster.
- Dissolved substances can be recovered by evaporation.
9. Self-test
- Does sugar dissolve in water?
- Name one substance that does NOT dissolve in water.
- Why does a nail sink but a ship float?
- Why do people float easily in the Dead Sea?
- How can you get back salt dissolved in water?
10. Answer key
-
Does sugar dissolve in water? Answer: Yes, sugar is soluble in water.
-
Name one substance that does NOT dissolve in water. Answer: Sand, oil, chalk powder, sawdust (any one).
-
Why does a nail sink but a ship float? Answer: Floating depends on density. A ship is shaped to displace a lot of water, making its overall density less than water. A nail is denser than water.
-
Why do people float easily in the Dead Sea? Answer: The Dead Sea is about 10 times saltier than regular sea water. The high salt content makes the water very dense, so objects float easily.
-
How can you get back salt dissolved in water? Answer: By evaporating the water. The salt will be left behind.
11. Quick revision
- Soluble: salt, sugar, honey, lemon juice. Insoluble: sand, oil, chalk.
- Density determines float or sink — not just weight.
- Shape affects how much water is displaced.
- Dead Sea: extremely salty, high density, easy to float.
- Dissolving is not disappearing — the substance is still there.
- Stirring and heating speed up dissolving.
- Experiment at home with simple materials to understand these concepts.
