Particle Model of MatterAQA GCSE Physics (8463)

Changes of State and the Particle Model

Work through the notes, try the practice questions, then take the quiz. The report tells you exactly what to revise next. (2026)

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Master the topic

Worked examples4 Key formulae1 Definitions6 Common mistakes4

Step-by-step worked examples

01.Density of a metal cube
Foundation
Question
A cube of side 4.0 cm has mass 432 g. Calculate its density.
Solution
1. 1
  Volume.
  $V = 4.0^3 = 64\,\text{cm}^3$
2. 2
  Density.
  $\rho = m/V = 432 / 64 = 6.75\,\text{g/cm}^3$
Answer
6.75 g/cm³ (= 6750 kg/m³). Probably zinc or pewter.
02.Density of an irregular stone
Higher
Question
A small stone has mass 75 g. Placed in a measuring cylinder, the water level rises from 50 cm³ to 80 cm³. Find density.
Solution
1. 1
  Volume.
  $V = 80 - 50 = 30\,\text{cm}^3$
2. 2
  Density.
  $\rho = 75/30 = 2.5\,\text{g/cm}^3 = 2500\,\text{kg/m}^3$
Answer
2500 kg/m³ — consistent with a typical sedimentary rock.
03.Mass conservation when ice melts
Foundation
Question
A student weighs an ice cube as 12 g, then lets it melt completely in a sealed container. What does the resulting water weigh?
Solution
1. 1
  Identify the principle.
  $\text{Mass is conserved during a state change.}$
2. 2
  Apply.
  $m_{\text{water}} = m_{\text{ice}} = 12\,\text{g}$
Answer
12 g (same as the ice). Mass is conserved.
04.Evaporation vs boiling
Foundation
Question
Explain the difference between evaporation and boiling.
Solution
1. 1
  Evaporation.
  $\text{Evaporation: from the SURFACE of a liquid at ANY temperature.}$
2. 2
  Boiling.
  $\text{Boiling: throughout the bulk of a liquid at its BOILING POINT.}$
3. 3
  Visible difference.
  $\text{Bubbles form during boiling; evaporation is silent and invisible.}$
Answer
Evaporation: surface only, at any T. Boiling: throughout the liquid, only at the boiling point. Bubbles form during boiling only.

Key formulae

Density
$\rho = m / V$
- $\rho$
  — Density (kg/m³ or g/cm³)
- $m$
  — Mass (kg or g)
- $V$
  — Volume (m³ or cm³)
When to use
Use whenever any two of mass, volume and density are given. On AQA equation sheet.

Practice with flashcards

Card 1 of 60 known · 0 to review

Key definitions and keywords

DensityExaminer keyword: Mass per unit volume. Units: kg/m³ or g/cm³.
Eureka can (displacement can): A container with a side spout used to measure the volume of an irregular solid by displacement.
Melting pointExaminer keyword: The temperature at which a solid changes to a liquid (for a pure substance).
Boiling pointExaminer keyword: The temperature at which a liquid changes to a gas throughout its bulk (for a pure substance).
Physical change: A change that does not alter the chemical identity of the substance; reversible.
Sublimation: Direct change from solid to gas, skipping the liquid state.

Common mistakes and misconceptions

Mistake
Mixing g/cm³ with kg/m³ in the same calculation.
Why it happens
Forgetting to convert.
How to avoid it
Stay in one unit system. Convert at the start.
Mistake
Forgetting to dry the irregular object before weighing.
Why it happens
Wet from displacement.
How to avoid it
Weigh BEFORE displacement, or dry thoroughly before weighing.
Mistake
Thinking mass increases when ice melts (because water 'fills more space').
Why it happens
Confusing volume with mass.
How to avoid it
Volume can change; mass is conserved (same particles).
Mistake
Saying water 'boils' at room temperature.
Why it happens
Confusing evaporation with boiling.
How to avoid it
Water only boils at 100 °C (at 1 atm). Below this it evaporates from the surface.

Particle Model of MatterAQA GCSE Physics (8463)

Changes of State and the Particle Model

Work through the notes, try the practice questions, then take the quiz. The report tells you exactly what to revise next. (2026)

PreviousNext

Master the topic

Worked examples4 Key formulae1 Definitions6 Common mistakes4

Step-by-step worked examples

01.Density of a metal cube
Foundation
Question
A cube of side 4.0 cm has mass 432 g. Calculate its density.
Solution
1. 1
  Volume.
  $V = 4.0^3 = 64\,\text{cm}^3$
2. 2
  Density.
  $\rho = m/V = 432 / 64 = 6.75\,\text{g/cm}^3$
Answer
6.75 g/cm³ (= 6750 kg/m³). Probably zinc or pewter.
02.Density of an irregular stone
Higher
Question
A small stone has mass 75 g. Placed in a measuring cylinder, the water level rises from 50 cm³ to 80 cm³. Find density.
Solution
1. 1
  Volume.
  $V = 80 - 50 = 30\,\text{cm}^3$
2. 2
  Density.
  $\rho = 75/30 = 2.5\,\text{g/cm}^3 = 2500\,\text{kg/m}^3$
Answer
2500 kg/m³ — consistent with a typical sedimentary rock.
03.Mass conservation when ice melts
Foundation
Question
A student weighs an ice cube as 12 g, then lets it melt completely in a sealed container. What does the resulting water weigh?
Solution
1. 1
  Identify the principle.
  $\text{Mass is conserved during a state change.}$
2. 2
  Apply.
  $m_{\text{water}} = m_{\text{ice}} = 12\,\text{g}$
Answer
12 g (same as the ice). Mass is conserved.
04.Evaporation vs boiling
Foundation
Question
Explain the difference between evaporation and boiling.
Solution
1. 1
  Evaporation.
  $\text{Evaporation: from the SURFACE of a liquid at ANY temperature.}$
2. 2
  Boiling.
  $\text{Boiling: throughout the bulk of a liquid at its BOILING POINT.}$
3. 3
  Visible difference.
  $\text{Bubbles form during boiling; evaporation is silent and invisible.}$
Answer
Evaporation: surface only, at any T. Boiling: throughout the liquid, only at the boiling point. Bubbles form during boiling only.

Key formulae

Density
$\rho = m / V$
- $\rho$
  — Density (kg/m³ or g/cm³)
- $m$
  — Mass (kg or g)
- $V$
  — Volume (m³ or cm³)
When to use
Use whenever any two of mass, volume and density are given. On AQA equation sheet.

Practice with flashcards

Card 1 of 60 known · 0 to review

Key definitions and keywords

DensityExaminer keyword: Mass per unit volume. Units: kg/m³ or g/cm³.
Eureka can (displacement can): A container with a side spout used to measure the volume of an irregular solid by displacement.
Melting pointExaminer keyword: The temperature at which a solid changes to a liquid (for a pure substance).
Boiling pointExaminer keyword: The temperature at which a liquid changes to a gas throughout its bulk (for a pure substance).
Physical change: A change that does not alter the chemical identity of the substance; reversible.
Sublimation: Direct change from solid to gas, skipping the liquid state.

Common mistakes and misconceptions

Mistake
Mixing g/cm³ with kg/m³ in the same calculation.
Why it happens
Forgetting to convert.
How to avoid it
Stay in one unit system. Convert at the start.
Mistake
Forgetting to dry the irregular object before weighing.
Why it happens
Wet from displacement.
How to avoid it
Weigh BEFORE displacement, or dry thoroughly before weighing.
Mistake
Thinking mass increases when ice melts (because water 'fills more space').
Why it happens
Confusing volume with mass.
How to avoid it
Volume can change; mass is conserved (same particles).
Mistake
Saying water 'boils' at room temperature.
Why it happens
Confusing evaporation with boiling.
How to avoid it
Water only boils at 100 °C (at 1 atm). Below this it evaporates from the surface.

Changes of State and the Particle Model

Master the topic

Step-by-step worked examples

01.Density of a metal cube

02.Density of an irregular stone

03.Mass conservation when ice melts

04.Evaporation vs boiling

Key formulae

Practice with flashcards

Key definitions and keywords

Common mistakes and misconceptions

Changes of State and the Particle Model

Master the topic

Step-by-step worked examples

01.Density of a metal cube

02.Density of an irregular stone

03.Mass conservation when ice melts

04.Evaporation vs boiling

Key formulae

Practice with flashcards

Key definitions and keywords

Common mistakes and misconceptions