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Thermal properties and temperature Study Notes | CIE iGCSE Physics

Thermal properties and temperature Study Notes - CIE iGCSE Physics - 2025-2028 Syllabus

Thermal properties and temperature Study Notes | CIE iGCSE Physics

Thermal properties and temperature 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

  • 2.2.1 Thermal expansion of solids, liquids and gases
  • 2.2.2 Specific heat capacity
  • 2.2.3 Melting, boiling and evaporation

iGCSE Physics New Syllabus-Study Notes -All Topics

2.2.1 Thermal expansion of solids, liquids and gases

Core

  • Describe, qualitatively, the thermal expansion of solids, liquids and gases at constant pressure
  • Describe some of the everyday applications and consequences of thermal expansion

Supplement

  • Explain, in terms of the motion and arrangement of particles, the relative order of magnitudes of the expansion of solids, liquids and gases as their temperatures rise

Thermal Expansion:-

Overview:

Thermal expansion describes the tendency of most materials to increase in size when heated. This phenomenon arises from the increased kinetic energy of the particles within the material, causing them to vibrate more vigorously and move further apart.

Key Points:

  • Molecular Behavior:
    • When heated, particles gain energy, leading to increased vibration and movement.
    • Molecular spacing increases, but individual molecular sizes remain constant.
  • State-Dependent Expansion:
    • Solids: Expand slightly due to strong intermolecular forces.
    • Liquids: Expand more than solids due to weaker intermolecular forces.
    • Gases: Expand significantly due to negligible intermolecular forces.
  • Applications:
    • Liquid-in-glass thermometers: Utilize the expansion of liquids like mercury or alcohol to measure temperature.
    • Shrink-fitting: Used to assemble components like axles and wheels by heating the axle to expand it and then cooling it down within the wheel, creating a tight fit.
    • Opening tight-fit lids: Heating the lid can cause expansion, making it easier to open.
    • Bimetallic strips: Composed of two different metals bonded together; they bend when heated due to differential expansion, used in thermostats and fire alarms.

Measuring Temperature:

  • Principle: Changes in physical properties like volume and electrical resistance due to heating can be used to measure temperature.
  • Temperature Scales:
    • Celsius to Kelvin Conversion:
      • 0°C = 273 K
      • T (Kelvin) = 273 + T (Celsius)

Note: Water exhibits an anomalous expansion behavior, reaching maximum density at 4°C and expanding below this temperature.

Expansion of water
Till about 4°C, water normally contracts as it cools. However, between 4°C and 0°C, water actually expands. Water has a maximum density at 4°C.
This expansion can lead to a lot of problems, for example if the water is in a pipe and it freezes, it can cause the pipe to burst open.

2.2.2 Specific heat capacity

Core

  •  Know that a rise in the temperature of an object increases its internal energy.

Supplement

  • Describe an increase in temperature of an object in terms of an increase in the average kinetic energies of all of the particles in the object.
  • Define specific heat capacity as the energy required per unit mass per unit temperature increase; recall and use the equation
    $c = \frac{∆E}{m∆θ}$
  • Describe experiments to measure the specific heat capacity of a solid and a liquid. 

Internal Energy

  • Definition: The total energy of an object’s particles due to their motion and interactions.
  • Temperature: A measure of the average kinetic energy of the particles in an object.
  • Heating: Increases both internal energy and the average kinetic energy of the particles.

Specific Heat Capacity

  • Definition: The amount of energy required to raise the temperature of one kilogram of a substance by one degree Celsius.
  • Formula: $c = \frac{∆E}{m∆θ}$
    where: – c = specific heat capacity (J/kg°C) – ΔE = change in internal energy (J) – m = mass (kg) – Δθ = change in temperature (°C)
  • Unit: Joules per kilogram per degree Celsius (J/kg°C)

In essence, specific heat capacity describes how much energy a substance can absorb or release per unit mass for a given temperature change.

Key Points:

  • Substances with high specific heat capacities require more energy to heat up and cool down slowly.
  • Water has a high specific heat capacity, making it an effective coolant.
  • Specific heat capacity is an important property in thermodynamics and engineering applications.

2.2.3 Melting, boiling and evaporation

Core
  • 1 Describe melting and boiling in terms of energy input without a change in temperature
  •  Know the melting and boiling temperatures for water at standard atmospheric pressure
  • Describe condensation and solidification in terms of particles
  •  Describe evaporation in terms of the escape of more-energetic particles from the surface of a liquid
  • Know that evaporation causes cooling of a liquid

Supplement

  •  Describe the differences between boiling and evaporation
  •  Describe how temperature, surface area and air movement over a surface affect evaporation.
  • Explain the cooling of an object in contact with an evaporating liquid 

 Melting and Freezing

  • Melting: When a solid substance transitions into a liquid state, it is called melting.
  • Freezing: The reverse process, where a liquid transforms into a solid, is called freezing.
  • Melting/Freezing Point: Pure substances have a specific temperature at which they melt or freeze, known as the melting point or freezing point. For example, water’s melting/freezing point at standard atmospheric pressure is 0°C.

2. Boiling and Condensation

  • Boiling: This occurs when a liquid transforms into a gas.
  • Boiling Point:
     

    Like melting, pure substances have a distinct boiling point. Water boils at 100°C under standard atmospheric pressure.

  • Condensation: The process where a gas changes into a liquid. It happens when gas particles lose energy, slow down, and come together due to cooling.

3. Solidification

  • Solidification: The process of a liquid transforming into a solid.
  • Mechanism: Liquid particles lose energy, slow down, and arrange themselves in a tightly packed, ordered structure with strong intermolecular forces.

4. Evaporation

  • Evaporation: A process where high-energy particles near the surface of a liquid gain enough energy to overcome intermolecular forces and escape into the surrounding space as a gas.
  • Cooling Effect: Evaporation causes the remaining liquid to cool down because the escaping particles carry away energy.

5. Latent Heat

  • Note: The image mentions latent heat, which is the energy absorbed or released during a phase change without a change in temperature. While it’s no longer in the syllabus, it’s important to understand that this energy is used to break or form the intermolecular bonds between particles.

Key Points

  • Phase changes involve changes in the arrangement and energy of particles.
  • Temperature remains constant during phase changes as the energy is used to overcome intermolecular forces.
  • These phase changes are fundamental to understanding the behavior of matter in various states.
 
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