A Journey through States of Water — States, Evaporation and Condensation (1 of 3) · Learner pages

Lesson 1 · Compare three states of water

Distinguish state properties while recognising ice, liquid water and water vapour as the same substance.

Name or initials: ____________   Date: ____________

Water can occur as solid ice, liquid water or gaseous water vapour. A change of state changes some observable behaviour without making water a different substance.

1. Identify the substance. The three model panels represent states of water. An ice cube and the liquid formed when it melts are both water. Their different shapes and ability to flow do not prove they are different substances.
2. Compare shape and volume. On classroom timescales an unmelted ice cube keeps its shape when moved to another container. Liquid water takes its container’s shape. If it is transferred without spilling or appreciable evaporation, its volume is unchanged.
3. Include the gaseous state. Water vapour is invisible and can spread through available space in the air. A visible white mist is made of tiny droplets, not visible water-vapour gas. The text panel for gas is a symbol, not an empty container.
4. State what the model leaves out. These drawings compare everyday behaviour. They are not a microscopic packing model, and they do not show that ice and liquid water have the same density or that a change of state leaves volume unchanged. We are comparing shape at a fixed state.

Worked example: A learner moves an unmelted ice cube from a round bowl to a square dish; its own shape is unchanged. A separate 100 mL water sample is transferred between two containers without loss; its shape changes but its volume remains 100 mL. These observations compare two states, not two different chemical substances.

1. An ice cube melts to liquid water. The result is…

   1. The same substance in a different state · 2. A completely unrelated substance · 3. Water that no longer has mass

2. A liquid water sample is poured into a wider container without loss. What can change?

   1. Its volume must double · 2. Its substance must change · 3. Its shape and height, while its volume stays the same

3. Water vapour itself is…

   1. A solid block · 2. An invisible gas · 3. Always a visible white cloud

Discuss: Create a three-row state table with shape, spreading behaviour and a model limitation. Use supplied observations rather than heating water.

Explain or demonstrate

Compare the three states in a table. Explain why shape changes do not always mean a new substance, and name one property the drawing does not establish.

Evidence to include:

• Three states distinguished
• Substance identity preserved
• A model limit stated

Lesson 2 · Explain water disappearing from view

Distinguish evaporation from leakage or absorption and recognise evaporation at room temperature.

Name or initials: ____________   Date: ____________

Water can leave a liquid surface as invisible vapour. A surface becoming dry does not show that the water has ceased to exist. More than one process can reduce a puddle.

1. Consider more than one explanation. A puddle can shrink because water enters the ground, runs elsewhere or evaporates. Begin with observations and possible explanations. A shrinking puddle alone does not identify only one cause.
2. Follow water from a surface. The model plate holds water that becomes less visible as some changes to vapour and disperses in the air. The arrows represent movement into the air, not visible jets of vapour. A dry plate is not evidence that matter was destroyed.
3. Recognise everyday evaporation. A damp cloth or a small clean-water film can dry at room temperature. Boiling is not required. For an observation, use a safe small amount of clean water on a stable non-porous tray; no hot pan or sanitiser is needed.
4. Use a control and keep limits. Record the starting condition and the time, and check for spills or wetness beneath the tray. An intact non-porous tray helps test a seepage explanation. Observations should support a conclusion with stated conditions rather than prove every surface behaves the same.

Worked example: Two supplied records describe clean water on an intact non-porous tray: a wet surface at the start and a dry surface later, with no spill or moisture beneath it observed. This supports evaporation as an explanation. It does not prove that a puddle on soil loses water only by evaporation.

1. A wet tray dries with no observed spill. Evaporation means water has…

   1. Been destroyed · 2. Turned into the tray material · 3. Changed to vapour in the surrounding air

2. Can water evaporate at room temperature?

   1. No; only ice can evaporate · 2. Yes; boiling is not required · 3. No; it must always reach boiling first

3. A puddle on soil shrinks. Which conclusion is most careful?

   1. Absorption and evaporation may both contribute · 2. Evaporation is the only possible cause · 3. No water can enter soil

Discuss: Write an observation-and-explanation table for a drying tray. Include one alternative explanation and a check that would help distinguish it.

Explain or demonstrate

For a supplied dry-tray record, separate observations from an evaporation explanation and propose one check for an alternative pathway.

Evidence to include:

• Observed surface change stated
• Vapour explanation identified as an inference
• Spill or underside check proposed

Lesson 3 · Explain droplets on a cold surface

Explain condensation using the origin, state and position of water on a cold container.

Name or initials: ____________   Date: ____________

The air can contain invisible water vapour. Near a sufficiently cold surface, some of that vapour can become liquid droplets. This is a state change in water already present in the surroundings.

1. Locate the observation. The model shows a cold container with water and ice inside, plus droplets outside. These are different locations. Record “droplets on the outside” before proposing where those droplets came from.
2. Identify a possible source. Even clear-looking surrounding air can contain water vapour. Invisible gas is not the same as no water. The model’s arrow from air to the outside surface represents that possible source.
3. Explain the state change. Air near the cold surface can cool enough for some water vapour to condense. The outside droplets are liquid water. Cooling alone does not mean every surface will become wet under every humidity condition.
4. Connect other observations. Dew can form when a surface cools sufficiently relative to the surrounding moist air. A dry warm comparison container and a cold closed container help investigate the explanation. No boiling-water or heating setup is needed.

Worked example: In a supplied comparison, an initially dry closed cold bottle develops outside droplets, while a similar room-temperature bottle remains dry in the same room. This supports a role for the cold surface and surrounding air. A careful explanation still records the actual conditions and measurement limits.

1. Condensation is the change from…

   1. Ice to liquid water · 2. Water vapour to liquid water · 3. Liquid water to water vapour

2. Where can the water for outside droplets on a cold closed bottle come from?

   1. Water vapour in surrounding air · 2. The bottle creating water from nothing · 3. Only melted ice passing through an intact wall

3. What is the state of the visible droplets outside the bottle?

   1. Invisible gas · 2. A solid metal · 3. Liquid

Discuss: Draw two labelled regions: inside the container and surrounding air. Show the proposed source and state change for outside droplets, then state a useful comparison.

Explain or demonstrate

Explain the outside droplets in the supplied closed-bottle comparison. Include water’s origin, state change and a limit on the conclusion.

Evidence to include:

• Surrounding air identified
• Vapour-to-liquid transition stated
• Actual conditions acknowledged

Final check · Set 1

Try one set after the lessons. Use the other set after reviewing any errors.

1. Which state spreads through the available space without a fixed shape or volume?

   An unmelted ice cube / A rigid stone / Gas

2. Does “ice and water are the same substance” mean their density must be identical?

   Yes; their shape must also match / No; some properties differ between states / Yes; every property must match

3. Which activity fits this lesson?

   Evaporate flammable liquids / Observe a small amount of clean water on a stable tray / Sprinkle water on a hot pan alone

4. Why does a visible white plume not show that water-vapour gas is white?

   The visible part contains tiny liquid droplets / All gases must be white / The plume has no water in it

5. Which comparison is useful?

   Similar cold and room-temperature closed containers in the same surrounding air / Different containers in different weather with no records / Only the container colours

6. Does every cold object always develop visible water droplets?

   Yes; cold objects create unlimited water / Yes; humidity never matters / No; surface and air conditions matter

Final check · Set 2

Try one set after the lessons. Use the other set after reviewing any errors.

1. A visible white mist near water is evidence of…

   Tiny liquid droplets in the air / Water vapour becoming a visible gas / Water ceasing to exist

2. Which statement keeps the model’s limit clear?

   The gas panel proves no matter is present / The drawing proves all state changes preserve volume / The panels show everyday behaviour, not literal particle arrangements

3. A non-porous tray observation supports evaporation. What remains too broad?

   Reporting the tray’s condition / Naming the observation time / Claiming that all shrinking outdoor puddles lose water only this way

4. Which pairing is correct?

   Absorption: every liquid becomes a gas / Evaporation: liquid to gas; absorption: liquid enters another material / Evaporation: liquid vanishes from existence

5. Dew formation is related to…

   Liquid water turning into invisible gas only / Water vapour becoming liquid on a sufficiently cool surface / Every plant leaking all its internal water

6. Which statement keeps substance and state distinct?

   The vapour and condensed droplets are both water in different states / Condensation creates a new metal / A droplet has no mass because it came from gas