Unit 2: Properties of materials
Changes of state — HIA International - Grade 8 Revision Notes & Topical Questions
5 min read 8 parts Lesson 3 of 12 2 quizzes
Lesson summary
Changes of state — HIA INTERNATIONAL notes: Name the changes of state of water, use a thermometer and measuring cylinder correctly and describe a heating curve.ChangeFromToMeltingSolidLiquidFreezingLiquidSolidBoiling / evaporatingLiquidGasCondensingGasLiquidSublimationSolidGas di…
- Melting point
- Boiling point
- Water vapour
- Evaporation
- Condensation
- Bulb position
Section 1 of 8Changes of state
| Change | From | To |
|---|---|---|
| Melting | Solid | Liquid |
| Freezing | Liquid | Solid |
| Boiling / evaporating | Liquid | Gas |
| Condensing | Gas | Liquid |
| Sublimation | Solid | Gas directly |
Section 2 of 8Key temperatures
Melting point
Melting point the temperature at which a solid melts; the freezing point is the same temperature.
Ice
- Ice melts at 0 °C.
Boiling point
Boiling point the temperature at which a liquid boils; pure water boils at 100 °C at normal air pressure.
Steam
- Steam water heated to the point that it turns into a gas.
Water vapour
- Water vapour the invisible gas formed when water evaporates.
Section 3 of 8Evaporation compared with boiling
Evaporation
- Evaporation happens at the surface of a liquid at any temperature below the boiling point.
Rate
- Rate evaporation is faster when the water is warmer, the surface area is larger and the air is moving.
Boiling
- Boiling happens throughout the liquid at the boiling point, with bubbles of gas forming.
Condensation
- Condensation water vapour or steam touching a cold surface changes back to liquid water.
Section 4 of 8Measuring volume and temperature
Measuring cylinder
- Measuring cylinder used to measure volume of a liquid.
Meniscus
Meniscus the curve at the top of a liquid; read the volume from the bottom of the meniscus with your eye level with it.
Thermometer
- Thermometer the liquid inside expands and rises as it gets hotter.
Reading
- Reading keep your eye level with the top of the liquid and read the scale.
Bulb position
- Bulb position keep the bulb in the water, not touching the bottom of the beaker, to measure the water temperature.
Section 5 of 8Heating curve of water
1
Measure the water into a beaker and place a thermometer in it, held by a clamp stand.
2
Record the temperature in a table of time and temperature.
3
Heat the water with a Bunsen burner on a tripod and gauze.
4
Record the temperature every minute until the water is boiling vigorously.
5
Plot time on the horizontal axis and temperature on the vertical axis.
Rising section
- Rising section the temperature rises while the water is heated.
Flat section
- Flat section the temperature stays at 100 °C while the water boils, because the energy separates the particles.
Safety
- Safety wear safety spectacles and take care with hot water.
Section 6 of 8Physical changes
Reversible
- Reversible changes of state are physical changes and can be reversed.
No new substance
- No new substance no new substance forms.
Mass
- Mass the mass stays the same.
Section 7 of 8Key terms
| Term | Meaning |
|---|---|
| Melting point | The temperature at which a solid melts. |
| Boiling point | The temperature at which a liquid boils. |
| Evaporation | A liquid changing to a gas at its surface. |
| Condensation | A gas changing to a liquid. |
| Meniscus | The curve at the top of a liquid in a measuring cylinder. |
| Sublimation | A solid changing directly to a gas. |
Section 8 of 8Exam technique
1
The temperature rises during boiling — it stays constant while the energy separates the particles.
2
Evaporation only happens at 100 °C — it happens at any temperature at the surface.
3
Steam and water vapour are the same as hot water — they are the gas state of water.
4
Read the volume from the top of the meniscus — read from the bottom of the meniscus.
Marked practiceQuizzes for this lesson
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