Thermodynamics

• If two systems are each in thermal equilibrium with a third, they are in equilibrium with each other.

• This law forms the basis for defining temperature and using thermometers.

What is the zeroth law of thermodynamics?

• Energy cannot be created or destroyed, only transformed from one form to another.

• This is the principle of conservation of energy.

What is the first law of thermodynamics?

• Biological processes depend on temperature and are controlled thermodynamically.

• Core and surface body temperatures vary with time and activity level.

How does body temperature regulation relate to thermodynamics?

• Normal range is 36–37.5°C; 38–40°C may result from exercise or fever.

• Below 33°C risks hypothermia; above 42°C may cause irreversible organ damage.

What are typical human core temperatures and their effects?

• Temperature is a scalar physical quantity measured with a thermometer.

• The constant-volume gas thermometer is fundamental, using pressure readings to determine temperature.

How is temperature defined and measured?

• They rely on properties like liquid expansion (mercury), electrical resistance (platinum), or IR radiation.

• These are calibrated against standard gas thermometers.

What are practical thermometers based on?

• When two objects at different temperatures contact, energy flows until temperatures equalise.

• This net energy movement due to temperature difference is called heat

What is thermal equilibrium and heat transfer?

• It’s the energy from random atomic/molecular motion including vibration and rotation.

• Higher temperatures mean more motion and more thermal energy.

What is thermal energy?

• Heat naturally flows from hotter to colder bodies.

• This continues until both are at the same temperature (thermal equilibrium).

How is heat transferred between objects?

• As temperature increases, atoms move faster and further apart, causing objects to expand.

• Different materials expand at different rates depending on their expansion coefficient.

What is thermal expansion?

• Ideal gases have negligible particle volume and no intermolecular attraction.

• Their volume increases linearly with temperature at constant pressure.

What defines ideal gas behaviour?

• Volume increases linearly with temperature at constant pressure.

• More particles or higher temperatures result in greater volume.

What is Charles’ law?

• At constant temperature, pressure and volume are inversely related.

• Increasing pressure reduces volume and vice versa.

What is Boyle’s law?

• The law relates pressure, volume, and temperature to the number of gas particles.

• It applies equally to mixtures and pure gases, using total particle number.

What is the ideal gas law and how does it apply to mixtures?

• In a gas mixture, total pressure equals the sum of partial pressures of each component.

• Each partial pressure is the pressure each gas would exert alone in the same volume.

What is Dalton’s law of partial pressures?

• At low temperatures or small volumes, intermolecular forces cause condensation.

• This results in phase changes, violating ideal assumptions.

How do real gases deviate from ideal gas laws?

• It’s the constant pressure where liquid and vapour coexist at a given temperature.

• On phase diagrams, this is shown by flat lines at constant temperature.

What is saturated vapour pressure?

• It’s the thermal energy required for a phase change without changing temperature.

• Latent heat varies by substance and phase (fusion or vaporization).

What is latent heat and when is it used?

• It’s the energy needed to raise 1 kg of a substance by 1°C.

• It determines how much heat is gained or lost when temperature changes.

What is specific heat capacity?

• Sweat evaporates using water’s high latent heat, removing heat from the body.

• High atmospheric vapour pressure can hinder evaporation and cooling.

How does the body regulate temperature using sweat?

• Dew point is the temperature at which water vapour condenses from air.

• It depends on the actual vapour pressure being lower than the saturation level.

What is dew point and how is it related to humidity?

• It's the lowest temperature a surface can reach via evaporative cooling.

• It equals the air temperature when relative humidity is 100%.

What is wet-bulb temperature?

• Conduction transfers energy through direct contact and occurs in solids.

• Convection occurs in fluids with moving particles, and radiation involves electromagnetic waves needing no medium.

What are the three modes of heat transfer?