iGCSE Physics Kinetic particle model of matter Study Notes- 2025-2028 Syllabus
iGCSE Physics Kinetic particle model of matter Study Notes
iGCSE Physics Kinetic particle model of matter Study Notes at IITian Academy focus on specific topic and type of questions asked in actual exam. Study Notes focus on iGCSE Physics syllabus with following topic details
- 2.1.1 States of matter
- 2.1.2 Particle model
- 2.1.3 Gases and the absolute scale of temperature
- iGCSE Physics 0625- Exam Style Practice Questions with Answer-Topic Wise-Paper 1
- iGCSE Physics 0625- Exam Style Practice Questions with Answer-Topic Wise-Paper 2
- iGCSE Physics 0625- Exam Style Practice Questions with Answer-Topic Wise-Paper 3
- iGCSE Physics 0625- Exam Style Practice Questions with Answer-Topic Wise-Paper 4
2.1.1 States of Matter
Core Concepts
- Know the distinguishing properties of solids, liquids and gases
- Know the terms for the changes in state between solids, liquids and gases (gas to solid and solid to gas transfers are not required)
2.1.1 States of Matter
Matter exists in one of three different states.
Characteristics of the States
| State | Characteristics |
| Solid | – Fixed shape and volume. – Strong forces of attraction between particles. – Have a fixed pattern (lattice). – Atoms vibrate but cannot change position. |
| Liquid | – Fixed volume but changes shape depending on container. – Weaker attractive forces than solids. – No fixed pattern. – Particles slide past each other. |
| Gas | – No fixed shape or volume; gases fill up their containers. – Almost no intermolecular forces. – Particles are far apart and move quickly. – Gases spread out to fill up the container and exert equal pressure on all surfaces. – They collide with each other and bounce in all directions. |
▪ Matter can change states via:
- Melting (solid to liquid) and freezing (liquid to solid), which occur at the melting point.
- Boiling (liquid to gas) and condensing (gas to liquid), which occur at the boiling point.
2.1.2 Particle model
Core Concepts
- Particle Structure: Describe the particle structure of solids, liquids, and gases in terms of the arrangement, separation, and motion of the particles. Represent these states using simple particle diagrams.
- Temperature and Particle Motion: Describe the relationship between the motion of particles and temperature, including the idea that there is a lowest possible temperature (−273 °C), known as absolute zero, where the particles have the least kinetic energy.
- Gas Pressure: Describe the pressure and the changes in pressure of a gas in terms of the motion of its particles and their collisions with a surface.
- Brownian Motion Evidence: Know that the random motion of microscopic particles in a suspension is evidence for the kinetic particle model of matter.
- Explanation of Brownian Motion: Describe and explain Brownian motion in terms of random collisions between the microscopic particles in a suspension and the particles of the gas or liquid.
Supplementary Concepts
- Forces, Distances, and Properties: Know that the forces and distances between particles (atoms, molecules, ions, and electrons) and the motion of the particles affect the properties of solids, liquids, and gases.
- Forces and Gas Pressure: Describe the pressure and the changes in pressure of a gas in terms of the forces exerted by particles colliding with surfaces, creating a force per unit area.
- Microscopic Particle Movement: Know that microscopic particles may be moved by collisions with light fast-moving molecules and correctly use the terms atoms or molecules as distinct from microscopic particles.
1. Particle Structure of Solids, Liquids, and Gases
The particle structure of solids, liquids, and gases can be described based on the arrangement, separation, and motion of particles:
| State | Particle Structure |
|---|---|
| Solid | • Particles are closely packed in a fixed arrangement. • Strong forces of attraction between particles. • Particles vibrate in fixed positions but do not move freely. |
| Liquid | • Particles are closely packed but not in a fixed arrangement. • Weaker forces of attraction than solids. • Particles can slide past each other. |
| Gas | • Particles are far apart and move randomly. • Negligible forces of attraction. • Particles move quickly and freely in all directions. |
2. Relationship Between Particle Motion and Temperature
The motion of particles is related to temperature:
- As temperature increases, particles gain more kinetic energy and move faster.
- At absolute zero (-273°C or 0 Kelvin), particles have the least possible kinetic energy and essentially stop moving.
3. Pressure of a Gas and Changes in Pressure
The pressure of a gas is caused by particles colliding with the walls of their container:
- When particles move faster (higher temperature), they collide more frequently and with greater force, increasing the pressure.
- When the volume of the container decreases, particles collide more often, also increasing the pressure.
4. Evidence for the Kinetic Particle Model of Matter
The random motion of microscopic particles in a suspension supports the kinetic particle model:
- This motion, known as Brownian motion, results from random collisions between microscopic particles and the particles of a gas or liquid.
5. Explanation of Brownian Motion
Brownian motion is caused by:
- Microscopic particles colliding randomly with fast-moving gas or liquid particles.
- This random collision provides evidence for the kinetic energy and motion of particles in matter.
6. Effect of temperature on pressure
The Pressure Law, also known as Gay-Lussac’s Law, states that for a fixed mass of gas at constant volume, the pressure of the gas is directly proportional to its absolute temperature.
Mathematical Expression
$P \propto T or \frac{P}{T} = \text{constant}$
Where:
- P = Pressure of the gas
- T = Absolute temperature (in Kelvin)
Example Calculation
If the pressure of a gas at 300 K is 100 kPa, and the temperature increases to 600 K, the new pressure can be calculated as:
$P_2 = \frac{P_1 \times T_2}{T_1} = \frac{100 \times 600}{300} = 200 \, \text{kPa}$
7. Forces and Distances Between Particles (Supplement)
The properties of solids, liquids, and gases depend on:
- The forces of attraction or repulsion between particles (atoms, molecules, ions, and electrons).
- The distances between particles and their motion.
8. Gas Pressure in Terms of Particle Forces (Supplement)
Gas pressure is the result of forces exerted by particles colliding with surfaces:
- Each collision creates a small force over a unit area, contributing to overall pressure.
9. Movement of Microscopic Particles (Supplement)
Microscopic particles can move due to collisions with light, fast-moving molecules:
- Atoms and molecules are distinct from larger microscopic particles, and their motion can shift microscopic particles in a suspension.
2.1.3 Gases and the Absolute Scale of Temperature
Core Concepts
1. Describe qualitatively, in terms of particles, the effect on the pressure of a fixed mass of gas of:
a. A change of temperature at constant volume
b. A change of volume at constant temperature
2. Convert temperatures between kelvin and degrees Celsius; recall and use the equation T (in K) = θ (in °C) + 273
Supplementary Concepts
- Recall and use the equation pV = constant for a fixed mass of gas at constant temperature, including a graphical representation of this relationship.
2.1.3 Gases and the Absolute Scale of Temperature
• Molecules in a gas move around randomly and very quickly.
• The temperature of a gas is related to the average kinetic energy of the molecules.
• The higher the KE of the molecules, the higher its temperature.
• For example, the average KE of a glass of water at 80°C is higher than the average KE of a glass of water at 30°C.
• Hence, the lowest possible temperature that can be achieved in this universe is -273°C (not infinity!).
• At this temperature, all molecules cease moving; hence, the average KE = 0.
• The motion of the molecules often causes them to collide with the surface of nearby walls.
• This collision causes a change in momentum when the molecule bounces off the wall (recall from the previous chapter: change in momentum over time gives you force).
• Each collision applies a force across a surface area of the walls.
• Recall from the previous chapter: force per unit area is pressure.
• Recall that Brownian motion is the erratic motion of small particles when observed through a microscope, which is caused by collisions between said particles and the molecules of the gas (or liquid).
• The SI unit of temperature is Kelvin. However, Celsius is more frequently used.
• You can convert Celsius to Kelvin using:
K = T°C + 273
Convert the following to Kelvin:
- a) -273°C
▶️ Answer/Explanation
Using the formula: $K = T^\circ C + 273$
Substituting $T = -273^\circ C:$
$K = -273 + 273 = 0 \, K$
Answer: 0 K
- b) 0°C
▶️ Answer/Explanation
Using the formula: $K = T^\circ C + 273$
Substituting $T = 0^\circ C:$
$K = 0 + 273 = 273 \, K$
Answer: 273 K
- c) 100°C
▶️ Answer/Explanation
Using the formula: $K = T^\circ C + 273$
Substituting $T = 100^\circ C:$
$K = 100 + 273 = 373 \, K$
Answer: 373 K
• When the temperature of a gas in a fixed container is increased, the KE (speed) of molecules increases.
• This causes the molecules to collide more frequently against the container, thus increasing pressure.
• However, if you decrease the volume while keeping the temperature of the gas constant (as in the case of the piston below), the pressure will increase.
• This is due to more collisions of the molecules with the container.
• This phenomenon can be described using Boyle’s Law:
$P_1V_1 = P_2V_2$
• The graph above shows the inverse relationship between pressure and volume of an ideal gas at constant temperature.