A Journey through States of Water · Lesson 1 of 8
Three States of Water
“Explore why ice, liquid water, and water vapour behave differently while remaining the same substance.”
• Identify ice, liquid water, and water vapour as three states of the same substance. • Compare the shape, flow, spreading, and volume of the three states. • Use observations to distinguish a solid, a liquid, and a gas. • Explain why water vapour can be present even when we cannot see it.
One substance, different forms
Imagine an ice cube floating in a glass of lemonade. You can pick up the cube, but you cannot pick up the liquid around it in the same way. Does that mean the ice is made of something different? Leave an ice cube in a cup and watch what happens. The cube becomes liquid water without anyone adding a new substance. Ice and liquid water are two states, or forms, of water.
A change in state changes how the material behaves. A solid piece of ice holds its own shape. Liquid water runs down the side of a cup and can splash. Water can also exist as a gas called water vapour. All three are water, even though their behaviour is different.
A form in which a substance exists, such as a solid, liquid, or gas. Water can exist as ice, liquid water, or water vapour.
Compare the states by observing them
Put an ice cube in a container, then move it to one of another shape. The cube keeps its shape. Pour the same amount of liquid water between the containers. It flows and takes the shape of the part of the container it fills. Pour some on a clean surface and it spreads. Now think about a small amount of water vapour entering a room: it spreads through the available air rather than remaining in one puddle-shaped region. These are the comparisons made in the chapter’s state investigation.
| Property | Ice: solid | Water: liquid | Water vapour: gas |
|---|---|---|---|
| Shape | Keeps its own shape | Takes the shape of its container | No fixed shape; fills available space |
| Flow | Does not flow as a liquid | Flows and can be poured | Moves and spreads through air |
| Spread | A cube does not spread across a surface | Can spread across a surface | Spreads throughout available space |
| Volume in an ordinary container | A piece keeps its size | The amount poured stays the same | Expands through the space available |
The water’s volume stays the same when you pour it into another container, provided none spills. Its shape changes, but that does not mean you have more or less water. A gas has no fixed shape and can spread into the space available to it.
States beyond water
A stone, a piece of wood, and glass are familiar solids. Milk and oil are familiar liquids. Oxygen and carbon dioxide are gases. Smells from cooking can reach you outside the kitchen because substances in the air spread and move. Many materials can change state under suitable conditions; we will look at examples such as wax and coconut oil when we study heating and cooling.
Water vapour is a gas that we cannot normally see. A visible whitish mist contains tiny liquid droplets; do not draw the vapour itself as a visible white cloud.
Problem
You pour a cup of water into a tall, narrow bottle. Has the water become a different substance or changed its amount?
- 1.The water now takes the shape of the part of the narrow bottle that contains it.
- 2.Provided none was spilled or added, it is still the same amount of liquid water.
- 3.Changing the container changes the liquid’s shape, not its identity.
Quiz
An ice cube melts in a cup. What does this show?
What happens when liquid water is poured into a differently shaped container?
Which observation best identifies a solid piece of ice?
Which statement about water vapour is correct?
Why might you smell cooking before reaching the kitchen?
Practice Problems
- Describe what you observe when an ice cube is left in a cup. What remains the same?
- Copy the comparison table and explain why liquid water has no fixed shape but an unchanged amount when poured without spilling.
- Compare how an ice cube, a spoonful of water, and water vapour spread.
- Give three examples of solids, two of liquids, and two of gases from everyday life.
- A child says that water vapour cannot be present in a room because it cannot be seen. Explain the mistake.
Key Takeaways
• Ice, liquid water, and water vapour are three states of the same substance. • A solid keeps its shape; a liquid flows and takes its container’s shape; a gas spreads through available space. • Water vapour can be present in the air even though it is invisible.
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Next · Lesson 2
Where Does Disappearing Water Go?