Thermodynamics and Chemical Kinetics

Only about 25% of the chemical energy from muscle metabolism is converted into useful kinetic energy for movement. The remaining 75% is released as heat, which is why exercise increases body temperature. This relatively low efficiency is similar to that of internal combustion engines and is a fundamental aspect of biological energy conversion.

A catalyst is a substance that increases the rate of a chemical reaction without being consumed in the process. It works by providing an alternative reaction pathway with lower activation energy, but remains unchanged after the reaction completes.

Exothermic reactions release heat energy into the surroundings - think "exit" for heat leaving the system. Endothermic reactions absorb heat. Heat is not liberated in all chemical reactions (some are endothermic), and substitution specifically refers to a reaction mechanism, not whether heat is released.

The refrigeration effect is the heat absorbed by the refrigerant as it evaporates at low pressure and temperature. This is the useful cooling produced by the system - the evaporator absorbs heat from the space being cooled.

Entropy is the thermodynamic property that quantifies the degree of randomness or disorder in a system. Higher entropy means greater molecular randomness. Enthalpy measures total heat content, chemical potential indicates potential for substance change, and Gibbs free energy determines spontaneity - none directly measure randomness.

Reactants are indeed the starting substances in a chemical reaction that undergo transformation to form products. They are written on the left side of a chemical equation. This is the standard definition in chemistry.

In an air cycle refrigeration system, low temperatures are produced by the expansion of compressed air through a turbine. As the air expands, it does work on the turbine blades, causing its internal energy and temperature to drop significantly.

Molar heat capacity is defined as the heat required to raise the temperature of 1 mole of a substance by 1 K (or 1°C), not 10 K. The statement incorrectly uses 10 K instead of 1 K, making it false.

Petrol engines operate on the Otto cycle (also called the spark-ignition cycle), which uses a spark plug to ignite the air-fuel mixture. Diesel engines use compression ignition (Diesel cycle), while the Carnot cycle is a theoretical thermodynamic cycle. The Otto cycle has four strokes: intake, compression, power, and exhaust.

Weber's law states that the JND (just noticeable difference) is a constant proportion of stimulus intensity. For example, a 10% change in weight is noticeable whether holding 100g or 1000g. James' law (not Weber's), the all-or-none principle (neurons firing), and law of diminishing returns (economics/productivity) are incorrect.

This process proceeds without any change in enthalpy or specific enthalpy (H), e.g. throttling process.

It is defined as a measure of the total energy of a thermodynamic system including the internal energy. It is a state function and an extensive property of the system.

This process is an idealized model of a thermodynamic process, which takes place infinitely slowly. Practically no real process is quasistatic.

All are state functions.

The kinetic energy is made up of different types of movements of particles. As the number of the movements are not same, K.E. has fluctuating value & not absolute value. The thermodynamic state function; like E, H, T, etc. depends on kinetic energy. Hence they have no absolute value.