Changes of State: Concept Map
≈ 24 minConcept Map
Organise the vocabulary, quantities and relationships into a connected model.
This extension applies that lens specifically to Changes of State.
Adding or removing energy changes the state of a substance, because it changes how strongly the particles are held together.
| Change | From → To | Energy |
|---|---|---|
| Melting | solid → liquid | taken in |
| Freezing (solidifying) | liquid → solid | given out |
| Evaporation | liquid → gas, at the surface, below boiling point | taken in |
| Boiling | liquid → gas, throughout the liquid, at the boiling point | taken in |
| Condensation | gas → liquid | given out |
| Sublimation | solid → gas, skipping the liquid | taken in |
Pure water melts at C and boils at C at sea level. Note that a change of state is a physical change: no new substance is made, and the change can be reversed.
Worked example — reading a heating curve from a table. A learner heats crushed ice and records the temperature every minute:
| Time (min) | 0 | 1 | 2 | 3 | 4 | 5 | 6 |
|---|---|---|---|---|---|---|---|
| Temp (C) | 0 | 0 | 0 | 4 | 9 |
- Minutes 0–2: the ice warms up from C to C. Still solid.
- Minutes 2–4: the temperature is stuck at C. This is the melting. Ice and water are both present.
- Minutes 4–6: all the ice is gone, so the liquid water now warms up.
The flat part of the table is the fingerprint of a change of state.
Altitude matters. Water boils at C at the coast in Durban, but at roughly C in Johannesburg, 1 753 m above sea level, because the air pushes down on the water less. That is why a pot of samp takes longer to cook on the Highveld — the water is genuinely not as hot.
Natural Sciences — Grade 8 — Concept Map: Drops of water form on the outside of a cold cooldrink bottle taken from the fridge. What change of state has taken place?
Natural Sciences — Grade 8 — Concept Map: What is the name of the change of state in which a solid turns directly into a gas, without becoming a liquid first?
Natural Sciences — Grade 8 — Concept Map: A beaker of crushed ice at C is heated steadily. Halfway through the experiment the beaker holds a mixture of ice and water. What temperature, in degrees Celsius, does the thermometer read at that moment?
Name the original topic being extended by this concept map lesson.
Which statement is the best evidence-led starting point for Changes of State: Concept Map?