CIE iGCSE Co-ordinated Sciences-P2.1.2 Particle model- Study Notes- New Syllabus
CIE iGCSE Co-ordinated Sciences-P2.1.2 Particle model – Study Notes
CIE iGCSE Co-ordinated Sciences-P2.1.2 Particle model – Study Notes -CIE iGCSE Co-ordinated Sciences – per latest Syllabus.
Key Concepts:
Core
- Describe the structure of solids, liquids and gases in terms of the arrangement, separation and motion of the particles and represent these states using simple particle diagrams
- Describe the relationship between the motion of particles and temperature
- Know that the random motion of particles (e.g. smoke particles or pollen grains, that can be viewed with a light microscope) in a suspension is evidence for the kinetic particle model of matter
Supplement
- Know that the forces and distances between particles and the motion of the particles affect the properties of solids, liquids and gases
- Describe and explain this motion (sometimes known as Brownian motion) in terms of random collisions between particles in the suspension and the much smaller, fast- moving particles of the gas or liquid
- Describe the pressure of a gas in terms of the forces exerted by particles colliding with surfaces, creating a force per unit area
CIE iGCSE Co-Ordinated Sciences-Concise Summary Notes- All Topics
Structure of Solids, Liquids, and Gases
The structure of matter can be explained in terms of arrangement, separation, and motion of particles.
| State | Arrangement | Separation | Motion |
|---|---|---|---|
| Solid | Particles in fixed, regular lattice | Very close together | Vibrate in fixed positions |
| Liquid | Particles irregularly arranged | Close together, but not fixed | Slide past each other (flow) |
| Gas | Particles randomly arranged | Far apart | Move freely and rapidly in all directions |
Particle Diagrams:
- Solids: Particles drawn close together in a fixed, regular pattern.
- Liquids: Particles close together but irregular, some gaps.
- Gases: Particles widely spaced, scattered randomly.
Relationship Between Motion of Particles and Temperature
Temperature is a measure of the average kinetic energy of the particles.
- As temperature increases, particles gain energy and move faster.
- In solids → vibrations increase. In liquids → particles slide faster. In gases → particles move rapidly, colliding more often.
- Cooling reduces particle motion; at very low temperatures, motion nearly stops (absolute zero).
Forces, Distances, and Properties of Solids, Liquids, and Gases
- In solids:
- Particles are very close → strong intermolecular forces.
- Properties: fixed shape, incompressible.
- In liquids:
- Particles close but not fixed → moderate forces.
- Properties: definite volume, flows, almost incompressible.
- In gases:
- Particles far apart → forces negligible.
- Properties: easily compressible, no fixed shape or volume.
Example :
A sealed balloon filled with air is heated. Explain what happens to the size of the balloon in terms of particle motion and forces.
▶️ Answer/Explanation
Step 1: Heating increases the temperature of the gas particles.
Step 2: Particles gain kinetic energy and move faster, colliding with the balloon walls more frequently and with greater force.
Step 3: The increased collisions cause the balloon to expand.
Final Answer: The balloon expands because heating increases particle motion, which increases pressure inside the balloon.
Example :
When a metal rod is heated, it expands slightly. Explain this in terms of the particle model.
▶️ Answer/Explanation
Step 1: In solids, particles are held in a fixed lattice by strong forces, but they vibrate about their positions.
Step 2: Heating increases the kinetic energy of the particles, so their vibrations become stronger.
Step 3: The increased vibration pushes particles slightly further apart, causing the solid to expand.
Final Answer: The rod expands because heating increases the vibration of particles, increasing average separation between them.
Brownian Motion
Brownian motion is the random, jittery movement of small particles (e.g., smoke or pollen grains) suspended in a liquid or gas, observed under a microscope.
Observation: Particles in a suspension do not move smoothly; instead, they move in unpredictable, zig-zag paths.
Explanation in Terms of the Kinetic Particle Model:
- The suspended particles are much larger than the particles of the surrounding gas or liquid, but still very small.
- The smaller, fast-moving particles of the liquid or gas collide randomly with the suspended particles.
- These collisions transfer momentum, causing the larger particles to move in a random, jittery way.
- Brownian motion provides visual evidence for the existence and random motion of particles in fluids, supporting the kinetic theory of matter.
Key Points:
- Motion is random and does not follow a fixed path.
- Movement is continuous as long as the surrounding fluid’s particles are in motion (i.e., above absolute zero).
- The faster the surrounding particles move (higher temperature), the more vigorous the Brownian motion.
Example :
Under a microscope, pollen grains in water move in a random, jittery way. Explain why this happens using the kinetic particle model.
▶️ Answer/Explanation
Step 1: Water molecules are very small and move randomly due to their kinetic energy.
Step 2: These fast-moving water molecules collide with the larger pollen grains from all directions.
Step 3: The unequal and random collisions push the pollen grains in unpredictable directions.
Final Answer: The jittery motion of the pollen grains (Brownian motion) is caused by random collisions with fast-moving water molecules, providing evidence for the kinetic theory of matter.
Pressure of a Gas
The pressure of a gas is the force exerted per unit area on the walls of its container due to collisions of gas particles.
Explanation Using the Particle Model:
- Gas particles are in constant, random motion.
- When particles collide with the walls of a container, they exert a force on the wall.
- Pressure is the average effect of many collisions per unit area of the container wall.
- More frequent or more energetic collisions lead to a higher pressure.
Relationship with Particle Properties:
- Increasing the number of particles (more collisions) increases pressure.
- Increasing the temperature increases particle speed, causing more forceful collisions → higher pressure.
- Decreasing the volume of the container increases collision frequency → higher pressure.
Equation Form:
$ \mathrm{Pressure, \, P = \frac{F}{A}} $
- \(\mathrm{F}\) = total force exerted by gas particles on the surface
- \(\mathrm{A}\) = area of the surface
Example :
A gas exerts a force of \(\mathrm{0.25 \, N}\) on a surface of area \(\mathrm{0.05 \, m^2}\). Calculate the pressure of the gas.
▶️ Answer/Explanation
Step 1: Use the formula: \(\mathrm{P = \frac{F}{A}}\)
Step 2: Substitute values: \(\mathrm{P = \frac{0.25}{0.05} = 5 \, Pa}\)
Final Answer: Pressure = \(\mathrm{5 \, Pa}\)
Example :
Explain why increasing the temperature of a gas in a sealed container increases its pressure, in terms of particle collisions.
▶️ Answer/Explanation
Step 1: Heating the gas increases the kinetic energy of the particles.
Step 2: Faster-moving particles collide with the container walls more frequently and with greater force.
Final Answer: The increased frequency and force of collisions raise the gas pressure.