Solids, Liquids & Gases

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Notes

Kinetic Theory

Matter consists of tiny particles in constant motion.
Arrangement and movement differ in solids, liquids, and gases.
**Solids**: particles packed closely in a regular pattern, vibrate in fixed positions.
**Liquids**: particles close but randomly arranged, slide past each other.
**Gases**: particles far apart, move randomly and quickly (~500 m/s).
Particle energy increases from solid to liquid to gas.

States of Matter

**Solid**: fixed volume and shape, high density.
**Liquid**: fixed volume, shape of container, medium density.
**Gas**: no fixed volume, shape of container, low density, easily compressed.
Density order: solid > liquid > gas (water is an exception).

State Changes

**Melting**: solid → liquid at melting point; heat energy increases particle movement.
**Freezing**: liquid → solid at same temperature as melting point.
**Boiling**: liquid → gas at boiling point; bubbles form throughout liquid.
**Evaporation**: liquid → gas at surface, below boiling point; faster with larger surface area and higher temperature.
**Condensation**: gas → liquid on cooling; particles lose energy and clump together.
During a state change, temperature remains constant because energy overcomes attractive forces, not increase kinetic energy.

Pressure & Temperature in Gases

Gas pressure results from particles colliding with container walls.
Increasing temperature increases particle kinetic energy, causing faster movement and more frequent collisions.
If container is flexible, volume increases as temperature rises (e.g., hot air balloon).
Increasing pressure (squeezing) decreases volume; particles collide more frequently.
Decreasing pressure increases volume.
Do not say particles expand; say they spread out.

Diffusion

Diffusion: net movement of particles from high to low concentration.
Occurs in gases and liquids due to random particle motion.
No energy input required; rate increases with temperature.
Diffusion is faster in gases than liquids because gas particles have more kinetic energy.
Example: potassium manganate(VII) in water spreads until evenly distributed.

Diffusion & Molecular Mass (Extended)

At same temperature, lighter gases diffuse faster than heavier ones.
Relative molecular mass (Mᵣ) determines rate: lower Mᵣ → faster diffusion.
Example: ammonia (Mᵣ=17) diffuses faster than hydrogen chloride (Mᵣ=36.5).
In a tube, ammonium chloride forms closer to the HCl end because NH₃ travels further.

Particle arrangement in solids, liquids, and gases.

Practice questions

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1.Which of the following statements about a specific mass of a liquid at room temperature is correct?
Easy
- AIt has a fixed volume.
- BIt has a fixed shape.
- CIts particles are in fixed positions.
- DIts volume is the same as that of an equal mass of gas.
2.In which of these substances are the particles close together and moving slowly past each other?
Easy
- AIce
- BAir
- CSteam
- DWater
3.The statement 'The particles moved slowly from an area of high concentration to an area of low concentration' describes which process?
Easy
- ADiffusion of a substance in a liquid
- BThe particles of a solid during melting
- CA liquid being frozen
- DDiffusion of a substance through air
4.A small amount of bleach spilled on a kitchen floor. After a while the floor was dry and the whole kitchen smelled of bleach. Which processes have occurred?
Easy
- AEvaporation and diffusion
- BDistillation and diffusion
- CEvaporation only
- DDiffusion only
5.As the temperature of air in a balloon increases, the volume increases. When the volume increases, the pressure inside the balloon:
Easy
- Aincreases
- Bdecreases
- Cstays the same
- Dbecomes zero
6.Water boils at 100 °C to form steam. Which statement about the particles of steam is correct?
Easy
- AThe arrangement of the molecules is regular.
- BThe molecules move quickly in random directions.
- CThe forces of attraction between the molecules are strong.
- DThe molecules are close together.
7.Which statement about diffusion is correct?
Easy
- AIt is a chemical change.
- BThe net movement of particles is from a region of lower concentration to a region of higher concentration.
- CThe particles spread in order with a fixed pattern.
- DThe net movement of particles is from a region of higher concentration to a region of lower concentration.
8.Which statements describe the arrangement of particles in a solid? 1. Particles are moving in all directions. 2. Particles are arranged in neat rows. 3. Particles can move past each other. 4. Particles vibrate about their positions.
Medium
- A1 and 2
- B2 and 4
- C1 and 3
- D2 only

More questions

9.The diagram shows a cup of hot chocolate made with boiling water. Which row correctly compares the particles of water in the air above the cup (steam) with those in the hot chocolate drink? (✓ = greater, × = not greater)
Medium
- AParticles move faster: ✓, Particles are closer together: ✓
- BParticles move faster: ✓, Particles are closer together: ×
- CParticles move faster: ×, Particles are closer together: ✓
- DParticles move faster: ×, Particles are closer together: ×
10.When a blue soluble crystal is placed in a beaker of water, which processes take place?
Medium
- AChemical process: ✓, Dissolving: ✓, Diffusion: ✓
- BChemical process: ×, Dissolving: ×, Diffusion: ✓
- CChemical process: ✓, Dissolving: ×, Diffusion: ✓
- DChemical process: ×, Dissolving: ✓, Diffusion: ✓
11.Substance X exists in three physical states as shown in the diagram. Which statement is correct? (State 1: solid, State 2: liquid, State 3: gas)
Medium
- AIn state 1 the particles vibrate around fixed positions but don't move.
- BDiffusion occurs in the phase change from state 1 to 2.
- CThe volume of the substance in state 3 is fixed.
- DCondensation occurs in the phase change from state 3 to 2.
12.The rate of diffusion of two gases, methane (CH4) and propene (C3H6), is measured. Which gas diffuses faster and why?
Hard
- APropene because its molecules are heavier and move faster.
- BMethane because it is a lighter molecule.
- CPropene because it is unsaturated and more reactive.
- DMethane because its molecules are smaller so they fit through holes more easily.
13.The diagram shows the heating curve for substance B. The regions are labelled P, Q, R and S. Using the kinetic particle model, which statement is correct?
Medium
- AIn region P, the particles gain kinetic energy and move around each other in an irregular arrangement.
- BIn region Q, the particles gain kinetic energy and move further apart as the substance is heated.
- CIn region R, thermal energy is used to overcome the attractive forces between the particles, which are in a random arrangement.
- DIn region S, thermal energy is used to overcome the attractive forces between the particles and they move far apart.
14.The rate of diffusion of four gases, neon (Ne), hydrogen chloride (HCl), ammonia (NH3), and oxygen (O2), is measured in a sealed container. What is the order of the rate of diffusion of the gases from slowest to fastest? (Relative molecular masses: Ne=20, HCl=36.5, NH3=17, O2=32)
Hard
- AHCl → O2 → Ne → NH3
- BO2 → HCl → NH3 → Ne
- CNH3 → Ne → O2 → HCl
- DNe → NH3 → HCl → O2
15.A student closed the lid tightly on an empty metal container which was used for paint. She heated the container over a Bunsen burner on a low flame for a few moments and observed the sides and top of the container bend outwards slightly. Which statement explains her observations?
Medium
- AThe heat increased the pressure inside the container.
- BThe heat deformed the metal which then bent.
- CThe heat made the container reduce in size.
- DMore air particles entered the container.
16.The kinetic theory of matter explores the spatial relationship between the particles in solids, liquids and gases. Which of the following processes causes the distance between particles to increase by the most?
Easy
- AMelting
- BFreezing
- CVaporising
- DCondensation
17.Substance X can occur in three different physical states as shown in the diagram. State 1 is solid, state 2 is liquid, state 3 is gas. Which statement is correct?
Medium
- AIn state 1 the particles vibrate around fixed positions but don't move.
- BDiffusion occurs in the phase change from state 1 to 2.
- CThe volume of the substance in state 3 is fixed.
- DCondensation occurs in the phase change from state 3 to 2.
18.A sample of gas is trapped in a syringe. The volume of the gas is 50 cm³ at a pressure of 100 kPa. The plunger is pushed so that the volume decreases to 25 cm³ while the temperature remains constant. What is the new pressure of the gas?
Hard
- A50 kPa
- B100 kPa
- C200 kPa
- D400 kPa
19.A student places a drop of blue ink into a beaker of still water. Over time, the ink spreads throughout the water. Which statement best explains this observation?
Medium
- AThe ink particles are less dense than water and rise.
- BThe water particles push the ink particles around.
- CThe ink particles move randomly from an area of high concentration to low concentration.
- DThe ink dissolves chemically in the water.
20.The table gives the melting and boiling points of four substances. Which substance is a liquid at 25 °C?
Hard
- AA (melting point -10 °C, boiling point 60 °C)
- BB (melting point 0 °C, boiling point 100 °C)
- CC (melting point 30 °C, boiling point 200 °C)
- DD (melting point -20 °C, boiling point -5 °C)
21.Which of the following best describes the movement of particles in a liquid?
Easy
- AThey vibrate about fixed positions.
- BThey move quickly in all directions and are far apart.
- CThey move around each other but remain close together.
- DThey do not move at all.
22.Two gas jars are connected as shown. One contains bromine vapour (orange-brown), the other contains air. After 5 minutes, the colour is evenly spread in both jars. Which process has occurred?
Medium
- AEvaporation
- BDistillation
- CDiffusion
- DCondensation
23.A sealed syringe contains 30 cm³ of gas at 20 °C. The syringe is heated to 60 °C at constant pressure. What is the new volume of the gas? (Assume pressure remains constant and the gas behaves ideally.)
Hard
- A10 cm³
- B34 cm³
- C90 cm³
- D60 cm³
24.What happens to the particles of a gas when the gas is compressed?
Easy
- AThe particles become smaller.
- BThe particles move faster.
- CThe particles get closer together.
- DThe particles increase in number.
25.A student places a crystal of potassium manganate(VII) in a beaker of water. After several hours, the entire solution is uniformly coloured. Which statement best explains this observation?
Medium
- AThe particles of potassium manganate(VII) are heavier than water and sink, spreading out.
- BThe particles of potassium manganate(VII) dissolve and then diffuse from a region of high concentration to low concentration.
- CThe water particles move into the crystal, causing it to expand and break apart.
- DThe particles of potassium manganate(VII) react with water to form a coloured product that spreads.
26.Which of the following best describes the arrangement of particles in a solid?
Easy
- AParticles are far apart and move quickly in all directions.
- BParticles are close together and arranged in a regular pattern.
- CParticles are close together but arranged randomly.
- DParticles are far apart and vibrate about fixed positions.
27.In an experiment to measure the rate of diffusion of gases, cotton wool soaked in concentrated ammonia solution and cotton wool soaked in concentrated hydrochloric acid are placed at opposite ends of a glass tube. A white ring of ammonium chloride forms. Where does the ring form?
Hard
- AExactly in the middle of the tube.
- BCloser to the ammonia end.
- CCloser to the hydrochloric acid end.
- DAt both ends of the tube.
28.A sealed syringe contains 30 cm³ of gas at 20°C. The syringe is heated to 60°C at constant pressure. What is the new volume of the gas? (Assume pressure remains constant and the gas behaves ideally.)
Medium
- A10 cm³
- B34 cm³
- C90 cm³
- D50 cm³
29.Which statement about the particles in a liquid is correct?
Medium
- AThe particles are arranged in a regular pattern.
- BThe particles vibrate about fixed positions.
- CThe particles are close together and can move past each other.
- DThe particles are far apart and move randomly.
30.The rate of diffusion of four gases, neon (Ne), hydrogen chloride (HCl), ammonia (NH₃), and oxygen (O₂), is measured in a sealed container. What is the order of the rate of diffusion from slowest to fastest?
Hard
- AHCl → O₂ → Ne → NH₃
- BO₂ → HCl → NH₃ → Ne
- CNH₃ → Ne → O₂ → HCl
- DNe → NH₃ → HCl → O₂
31.Which process is represented by the following description? 'A liquid changes into a gas at a specific temperature, with bubbles forming throughout the liquid.'
Easy
- AEvaporation
- BBoiling
- CCondensation
- DMelting
32.A student closed the lid tightly on an empty metal container. She heated the container over a Bunsen burner for a few moments and observed the sides and top bend outwards. She then allowed it to cool. Which statement explains the outward bending?
Hard
- AThe heat increased the pressure inside the container.
- BThe heat deformed the metal which then bent.
- CThe heat made the container reduce in size.
- DMore air particles entered the container.
33.The diagram shows a heating curve for a substance. Which region represents the change of state from solid to liquid?
Medium
- AA region where temperature increases with time.
- BA horizontal region where temperature remains constant.
- CA region where temperature decreases with time.
- DA region where the substance is in the gaseous state.
34.Which of the following is a correct statement about the movement of particles in a gas?
Easy
- AThe particles vibrate about fixed positions.
- BThe particles move slowly in a regular pattern.
- CThe particles move quickly in random directions.
- DThe particles do not move.
35.A small amount of bleach spilled on a kitchen floor. After a while, the floor was dry and the whole kitchen smelled of bleach. Which processes have occurred?
Medium
- AEvaporation and diffusion
- BDistillation and diffusion
- CEvaporation only
- DDiffusion only
36.In an experiment, a student places a drop of blue ink into a beaker of still water. Over time, the ink spreads throughout the water. Which statement best explains this observation?
Hard
- AThe ink particles are heavier and sink, then spread.
- BThe ink particles dissolve and then diffuse from high to low concentration.
- CThe water particles push the ink particles around.
- DThe ink particles react with water to form a blue solution.
37.What is the name of the process when a liquid changes into a gas at a specific temperature, with bubbles forming throughout the liquid?
Easy
- AEvaporation
- BBoiling
- CCondensation
- DMelting
38.Which of the following statements about diffusion is correct?
Easy
- ADiffusion only occurs in gases.
- BDiffusion is the net movement of particles from a region of lower concentration to a region of higher concentration.
- CDiffusion is the net movement of particles from a region of higher concentration to a region of lower concentration.
- DDiffusion requires an external energy input to occur.
39.A sealed syringe contains 30 cm³ of gas at 20 °C. The syringe is heated to 60 °C at constant pressure. What is the new volume of the gas? (Assume pressure remains constant and no gas escapes.)
Medium
- A10 cm³
- B30 cm³
- C34 cm³
- D90 cm³
40.Which of the following correctly describes the movement of particles in a liquid?
Medium
- AParticles vibrate about fixed positions.
- BParticles move quickly in all directions and are far apart.
- CParticles move around each other but remain close together.
- DParticles are stationary and arranged in a regular pattern.

Slides

Kinetic Theory of Matter

All matter is made of tiny particles in constant motion.
The arrangement and movement of particles determine the state of matter.
Solids, liquids, and gases have different physical properties due to particle behavior.

Which statement about solids is correct?

Particles are far apart and move quickly.
Particles are close together in a regular pattern and vibrate in fixed positions.
Particles are close together but randomly arranged and slide past each other.
Particles have no fixed positions and move randomly.

Properties of Liquids and Gases

Liquids: fixed volume, shape of container, particles close but randomly arranged, can slide past each other.
Gases: no fixed volume, take shape of container, particles far apart, move quickly in all directions.
Gases are easily compressed because there is lots of space between particles.

Which of these are true about liquids?

Liquids have a fixed volume.
Liquids have a fixed shape.
Particles in a liquid are arranged randomly.
Particles in a liquid vibrate about fixed positions.

State Changes

Melting: solid → liquid (heat energy absorbed, particles gain kinetic energy).
Boiling: liquid → gas (at boiling point, bubbles form throughout liquid).
Evaporation: liquid → gas at surface, below boiling point.
Condensation: gas → liquid (cooling, particles lose energy).
Freezing: liquid → solid (same temperature as melting point).

During melting, particles absorb thermal energy which is converted to ____ energy, allowing them to move more.

Heating and Cooling Curves

Heating curve: shows temperature change as a substance is heated.
Horizontal sections: during state changes, temperature stays constant because energy is used to overcome forces between particles.
Cooling curve: mirror image of heating curve.

On a heating curve, why does temperature remain constant during a state change?

Particles stop moving.
Thermal energy is used to overcome attractive forces between particles.
The substance loses heat.
The particles expand.

Pressure and Temperature in Gases

Gas pressure is caused by particles colliding with container walls.
Increasing temperature increases particle kinetic energy → more frequent collisions → pressure increases (if volume constant).
If container is flexible, volume increases as temperature rises (e.g., hot air balloon).
Increasing pressure (squeezing) decreases volume; particles hit walls more often.

What happens to the volume of a gas if the temperature is increased at constant pressure?

Volume decreases.
Volume stays the same.
Volume increases.
Volume becomes zero.

Diffusion

Diffusion: net movement of particles from high to low concentration.
Occurs in liquids and gases due to random particle motion.
No energy input required; happens faster at higher temperatures.
Diffusion is faster in gases than liquids because gas particles have more energy and move faster.

Which statements about diffusion are correct?

Diffusion is the movement of particles from low to high concentration.
Diffusion occurs in both liquids and gases.
Diffusion is faster at higher temperatures.
Diffusion requires an input of energy.

Diffusion and Molecular Mass (Extended)

At the same temperature, lighter gases diffuse faster than heavier gases.
Relative molecular mass (Mr) determines speed: lower Mr → faster diffusion.
Example: ammonia (Mr=17) diffuses faster than hydrogen chloride (Mr=36.5).
In a tube, ammonium chloride forms closer to the HCl end because NH3 travels further.

Ammonia (Mr=17) diffuses ____ than hydrogen chloride (Mr=36.5).

Which gas diffuses fastest?

Hydrogen (H2, Mr=2)
Oxygen (O2, Mr=32)
Carbon dioxide (CO2, Mr=44)
Chlorine (Cl2, Mr=71)

Summary: Key Differences Between States

Solids: fixed shape & volume, high density, particles vibrate in fixed positions.
Liquids: fixed volume, shape of container, medium density, particles slide past each other.
Gases: no fixed volume, low density, particles move quickly and randomly.

A substance has particles that are far apart and move rapidly in all directions. What is its state?

Solid
Liquid
Gas
Plasma

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