States of Matter: Properties and Energy

The law of conservation of energy states that energy cannot be created or destroyed, only transferred or converted from one form to another. In chemical reactions, this means that the energy change associated with the reaction is the result of the transfer of energy from one form to another, such as from chemical bonds to heat or vice versa.

Endothermic reactions absorb energy from the surroundings, typically in the form of heat, and are often associated with a temperature decrease. Exothermic reactions release energy to the surroundings, typically in the form of heat, and are often associated with a temperature increase.

The change in enthalpy (ΔH) represents the amount of heat energy released or absorbed during a chemical reaction at constant pressure. A positive ΔH indicates an endothermic reaction, while a negative ΔH indicates an exothermic reaction.

Activation energy is the minimum amount of energy required for a collision between reactant particles to result in a reaction. A low activation energy means that the reaction occurs at a significant rate, while a high activation energy means that the reaction occurs at a much slower rate.

The collision theory states that particles of reactants need to collide in the correct orientation and with enough energy to break the bonds and trigger a reaction. If the particles have incorrect orientation or lack of energy, no reaction occurs and the particles bounce off each other.

A high rate of reaction means that particles are combining at a faster rate, while a low rate of reaction means that particles are combining at a slower rate. The rate of reaction can be measured by the rate of disappearance of reactants or the rate of appearance of products.

Thermodynamic calculations, such as the calculation of energy released, provide a quantitative measure of the energy changes associated with a chemical reaction, and are essential for understanding the thermodynamics of chemical reactions.

Kinetic energy is the energy of motion, while potential energy is the energy stored in the bonds of atoms and molecules. In chemical reactions, the conversion of potential energy to kinetic energy, or vice versa, is a key aspect of the energy changes that occur.

The formation of products requires less energy than it took to break the bonds of the reactants, resulting in an exothermic reaction. The excess energy is released as heat, and the change in enthalpy is negative.

The molar mass of a reactant is used to calculate the number of moles of reactant, which is then used to calculate the energy released or absorbed during a chemical reaction.