♡ Topic 14_Particle model ♡

• Definition of density:

  • The mass per unit volume of a material
  • ⍴=m/v
  • Density (kg/m³) = Mass (kg) / Volume (m³)
• State of matter:

  • A form in which matter can exist, based on the particle arrangement in a substance
• States of matter in order of density of atoms:

  • Least dense: Gas
  • Liquid
  • Most dense: Solid
• Kinetic theory explaining the structure of liquids:

  • Particles have kinetic energy
  • Free to move and move around in random directions at slow speeds
• Movement of particles in a solid:

  • Vibrate around a fixed position due to lack of kinetic energy to move freely
• Structure of particles in a gas:

  • Almost no forces between particles
  • Completely free to move at high speeds in random directions
• Conserved quantity during a change of state: Mass
• Difference between change of state and chemical change:

  • Change of state can be reversed
  • Chemical change cannot be easily reversed
• Internal energy of a substance:

  • Energy stored by particles
  • Sum of total kinetic and potential energies in the system
• Heating a substance can:

  1. Raise its temperature

  2. Change the state of the substance
• Factors determining temperature change of a system:

  1. Mass of substance being heated

  2. Type of material (Specific heat capacity)

  3. Energy inputted into the system
• Sublimation:

  • Solid turns directly into a gas
• Heating causing a substance to change state:

  • Gives particles more potential energy to break attraction bonds, leading to a change of state
• Heating increasing substance temperature:

  • Increases thermal energy
  • Gives particles more kinetic energy, making them move faster
• Equation for energy change when heating a substance:

  • ΔE = m c Δ��
  • Energy (J), Mass (kg), Specific Heat Capacity (J/kg/°C), Temperature (°C)
• Specific heat capacity:

  • Energy needed to increase the temperature of 1kg of a substance by 1°C
• Specific latent heat:

  • Energy needed to change the state of 1kg of a substance with no change in temperature
• Equation for energy required to change state:

  • Energy (J) = Mass (kg) x Specific latent heat (J/kg)
  • E = mL
• Particles in a gas have almost no forces between them, allowing them to move freely at high speeds in random directions
• Gas pressure is explained by the motion of particles colliding with the walls of a container, exerting a force at a right angle to the container, thus causing pressure
• The equation to calculate pressure is: Pressure (Pa) = Force (N) / Area (m²) or P = F / A
• Increasing the temperature of a gas held at constant volume will result in an increase in gas pressure
• Pressure increases as temperature increases at a constant volume due to the increase in kinetic energy of molecules, leading to more frequent collisions and greater force
• The average kinetic energy of gas molecules is affected by the temperature of the gas. A higher temperature leads to higher average kinetic energy of the molecules
• The force exerted by the pressure of a gas on the walls of its container acts at right angles to each surface of the container and increases as pressure increases
• In a low-pressure gas (A) and a high-pressure gas (B), gas A has a higher rate of collisions per second compared to gas B
• For a fixed mass of gas at a constant temperature, the product of pressure and volume remains constant (p V = constant)
• Increasing the volume of a gas decreases pressure because the molecules become more spread out, reducing the rate of collision and force exerted on the container
• The unit used for pressure is Pascal (Pa)
• Doing work on a gas increases its internal energy, potentially leading to an increase in temperature
• To convert between degrees Celsius and Kelvin: Kelvin = Celsius + 273, Celsius = Kelvin - 273
• Absolute zero is -273 °C, where particles have no kinetic energy and do not move
• The equation P₁ × V₁ = P₂ × V₂ can be used to calculate pressure/volume for a gas with fixed mass and constant temperature
• When air is pumped into a bike pump, the temperature of the air inside increases because work is done on the gas during compression, increasing its internal energy and average kinetic energy of molecules