P1

Page 1

• OCR (A) Physics GCSE

• Topic P1: Matter Summary Notes

Page 2: The Particle Model

How & Why the Atomic Model Has Changed Over Time

• 1800: Dalton proposed that everything is made of indivisible tiny spheres called atoms.

• 1897: JJ Thomson discovered the electron, leading to the Plum Pudding Model.

• 1911: Rutherford revealed that most of the atom is empty space through the Gold Foil Experiment.

• 1913: Rutherford's Model was developed further.

Page 3: Structure & Size of the Atom

• Atom Structure:

  • Positively charged nucleus (protons + neutrons)

  • Negatively charged electrons orbiting the nucleus

• Subatomic Particle Details:

  • Proton: Mass = 1, Charge = +1

  • Neutron: Mass = 1, Charge = 0

  • Electron: Mass ≈ 0 (0.0005), Charge = -1

• Size: Atom = 10^(-10) meters; nucleus is 10,000 times smaller.

• Density Formula:

  • Density (ρ) = Mass (kg) / Volume (m³)

• Density Differences:

  • Solids & liquids have higher densities compared to gases due to closer particle spacing.

  • Ice is less dense than water.

Page 4: Changes of State

Conservation of Mass

• Mass remains constant during changes of state (e.g., 20g liquid = 20g gas).

• Changes are physical and reversible.

Heating a System

• Heat vs Temperature:

  • Temperature measures average kinetic energy.

  • Heat is energy measured on an absolute scale.

• Heat absorption outcomes:

  • Increases temperature at the same state.

  • Changes state at constant temperature.

Specific Heat Capacity & Latent Heat

• Specific Heat Capacity (c):

  • Energy to raise 1kg by 1ºC.

  • Formula: E = mc∆T (J/kg°C).

• Specific Latent Heat (l):

  • Energy to change 1kg without temperature change.

  • Formula: E = ml (J/kg).

Page 5: Pressure (Physics Only)

Molecule Motion

• Particles in fluids move randomly.

• Pressure formula: Pressure (p) = Force/Area.

• Pressure increases with more frequent and forceful particle collisions.

Temperature & Pressure

• At constant volume: Pressure ∝ Temperature (p ∝ T).

• Increasing temperature increases pressure due to particle speed.

Volume & Pressure

• At constant temperature: Pressure ∝ 1/Volume (p ∝ 1/V).

Temperature, Volume & Work

• At constant pressure: Volume ∝ Temperature (V ∝ T).

• Work done on fluids increases temperature.

Page 6: Increasing Pressure & Temperature

• Adding gas = more particle collisions = higher pressure.

• Reducing volume = more frequent collisions = higher pressure.

• Earth's Atmosphere:

  • Isothermal and uniform density.

• Atmospheric Pressure decreases with altitude due to fewer air molecules.

Floating & Sinking

• Objects float if weight < displaced fluid weight.

• Buoyancy counteracts weight of floating objects.

Page 7: Pressure & Buoyancy

Pressure & Depth

• Water depth increases weight of the water column = higher pressure.

• Pressure due to liquid column = Height × Density × g (10).

• Example: A ping pong ball floats due to having less density than water.