Thermal Equilibrium and States of Matter

Thermal Equilibrium

• Energy transfer occurs from regions of high temperature to regions of low temperature.
• When objects are at the same temperature, there is no net transfer of heat between them.

Temperature Scales

• Celsius scale is commonly used.
• Fahrenheit scale is used in the USA.
• Kelvin scale is the absolute scale, meaning it starts from zero.
• Kelvin (K) is the SI unit of temperature.
• Convert from Celsius to Kelvin by adding 273.
• Celsius scale is based on the freezing point and boiling point of water, however, these points are not absolute as they are dependent on pressure.

States of Matter

• Solid: Fixed lattice, particles vibrate in a fixed position.
• Liquid: Particles can flow past each other, not fixed in position.
• Gas: Particles are widely spaced, minimal forces between particles except during collisions, random linear motion.

Brownian Motion

• Smoke cell experiment: Observing visible smoke particles moving randomly in a container of air.
• Conclusion: Smoke particles collide with invisible, much smaller air particles, leading to their random movement.

Internal Energy

• Sum of kinetic energy and potential energy of all particles in a substance.
• Internal energy is denoted by 'u'.
• Potential energy component increases when particles are further apart due to breaking molecular bonds.

Specific Heat Capacity

• Energy required to raise the temperature of 1 kilogram of a substance by 1 Kelvin.
• Specific heat capacity is 'c' and has units of meters squared per second squared per kelvin (m²⋅s⁻²⋅K⁻¹).
• Formula: c = energy (J) / (mass (kg) * change in temperature (K) )

Heating Curve

• Shows temperature changes of a substance as heat is added.
• Solid: Kinetic energy increases with increasing temperature.
• Melting (Solid to Liquid): Temperature remains constant while potential energy increases as molecular bonds break.
• Liquid: Kinetic energy increases with increasing temperature.
• Evaporation (Liquid to Gas): Temperature remains constant while potential energy increases as particles are pushed further apart.
• Gas: Kinetic energy increases with increasing temperature.

Determining Specific Heat Capacity

• Experiment Setup:
  • Electrical cell connected to a variable resistor, ammeter, and voltmeter.
  • Immersion heater fully submerged in a liquid within an insulated container.
• Procedure:
  • Measure the mass of the liquid using a top pan balance.
  • Measure the current (I) and voltage (V) using an ammeter and voltmeter respectively.
  • Measure the temperature of the liquid at regular intervals using a thermometer and a stop clock.
  • Stir the liquid regularly to ensure even temperature distribution.
• Data Analysis:
  • Plot a graph of temperature against time.
  • Determine the gradient of the graph (representing the rate of change of temperature).
• Specific Heat Capacity Equation:
  • e = mcΔθ (where e = energy, m = mass, c = specific heat capacity, Δθ = change in temperature)
  • Power (P) = Energy (e) / Time (t)
• Relationship between Power and Gradient:
  • P = mc * gradient
• Specific Heat Capacity Calculation:
  • c = P / (m * gradient)
  • c = (V * I) / (m * gradient) (using measured current and voltage)

Specific Latent Heat of Fusion

• Definition: Energy required to change the state of a substance from solid to liquid at constant temperature (melting).
• Experiment Setup:
  • Similar circuit to specific heat capacity experiment, but with a funnel filled with ice, a heater, and a beaker to collect melted ice.
  • A control beaker containing ice is used to measure the amount of ice melting due to room temperature.
• Procedure:
  • Measure the current (I) and voltage (V) using an ammeter and voltmeter.
  • Allow the heater to melt ice for a set time measured with a stopwatch.
  • Measure the mass of the melted ice.
  • Subtract the mass of the ice melted in the control beaker to account for melting due to room temperature.
• Specific Latent Heat of Fusion Calculation:
  • lf = Energy (e) / Mass (m)
  • lf = (V * I) / (m)

Specific Latent Heat of Vaporization

• Definition: Energy required to change the state of a substance from liquid to gas at constant temperature (vaporization).
• Experiment Setup:
  • Similar circuit to specific heat capacity and specific latent heat of fusion experiments, but with a condenser to collect the vaporized liquid.
• Procedure:
  • Measure the current (I) and voltage (V) using an ammeter and voltmeter.
  • Heat the liquid in the condenser until it reaches its boiling point.
  • Measure the mass of the liquid that has vaporized and condensed in the collecting flask.
• Specific Latent Heat of Vaporization Calculation:
  • lv = Energy (e) / Mass (m)
  • lv = (V * I * t) / (m) (using the measured current, voltage, and heating time)

This quiz covers the fundamental concepts of thermal equilibrium, temperature scales, states of matter, and Brownian motion. It includes key definitions and principles that govern energy transfer and the behavior of particles in different states. Test your understanding of these important scientific concepts.