[UNIT 3] CHEM - Energy

Renewable

Energy sources that can be replaced within a human lifetime, e.g., biofuel, wind, hydroelectric, geothermal, tidal, solar.

Non-renewable

Energy sources that cannot be replaced or take much longer than a human lifetime to replace, e.g., fossil fuels (coal, oil, gas), nuclear fuel.

Exothermic Reactions

Reactions that transfer energy to the surroundings, increasing temperature, e.g., combustion of fuels, respiration.

Endothermic reactions

Reactions that absorb energy from the surroundings, decreasing temperature, e.g., thermal decomposition reactions, photosynthesis.

Activation energy

Minimum energy required for a reaction to occur, represented as a 'hump' on the energy profile.

Bond enthalpy

Energy needed to break and form bonds, endothermic and positive △H for bond breaking, exothermic and negative △H for bond formation.

Specific heat capacity

Amount of energy needed to raise the temperature of 1kg of a substance by 1℃ or 1K, formula:q=mcΔT.

Complete combustion

Happens with sufficient oxygen, producing carbon dioxide and water, e.g., Fuel+O2→CO2+H2O.

Incomplete combustion

Occurs with insufficient oxygen, producing carbon monoxide and soot, e.g., Fuel+O2→CO+H2O.

States of Matter

Solid, liquid, gas; Heat is energy transfer, while temperature is the average kinetic energy of particles in a substance.