Useful Notes for the Science CAT

Exothermic Reaction

Reactions that release energy from the system to the surroundings, characterized by temperature increases and the release of thermal energy. The reactants have higher energy than the products.

Steps for Exothermic Reactions

1. If no external heat is provided, energy comes from system

2. Chemical Energy is converted into Thermal Energy

3. Thermal Energy is released and lost to surroundings

4. Enthalpy Changes

Endothermic Reaction

Reactions that absorb energy from the surroundings to the system, characterized by temperature decreases. The products have higher energy than the reactants.

Drawing Graphs

1. Draw axis and label (e.g. Enthalpy for y-axis and Progress of Reaction for x-axis)

2. Draw reactant and product lines

3. Draw curve between the two, with the top of your curve lining up with the Activation Energy

4. Draw and label activation energy and enthalpy change 

   • In endothermic, the enthalpy change (positive) is between the reactants and products and the activation energy is between the reactants and the top peak.

   • In exothermic, the enthalpy change (negative) is between the reactants and the products and the activation energy is between the reactants and the top peak (not the full graph).

Enthalpy Change

The overall change in energy during a reaction, positive for endothermic reactions and negative for exothermic reactions.

Alcohols

A group of compounds with similar chemical properties containing the hydroxyl (-OH) group, such as methanol, ethanol, and propanol. The general formula for alcohol is C_nH_2n+1OH.

Heat of Combustion

The amount of heat released during a combustion reaction, used to calculate the enthalpy change. It can be determined for alcohols using the formula ΔH = -mcΔT.