Thermochemistry

Conservation of Energy Whatever changes occur in energy from one type to another, the total amount of energy remains constant Energy cannot be created or destroyed

Energy in Reactions In every type of change, there is a change in energy Energy change usually more noticeable in chemical changes Energy, or heat, of a reaction is symbolized by H H is the heat of the products minus the heat of the reactants

Exothermic If reactants have more chemical energy than the products, then energy must be lost in reaction 2H2 + O2  2H2O + energy This release in heat energy causes the substances to become hot H is a negative number

What is the H for the reaction shown by the diagram?

Endothermic Reactions If products have more chemical energy than reactants, energy must be absorbed 2NaCl + energy  2Na + Cl2 The absorption of heat causes substances to feel cold H is a positive number

What is the H for the reaction shown in the diagram?

Activation Energy Even though some reactions are exothermic it may still require a little energy to start it off This starting energy is called ACTIVATION ENERGY

What is the activation energy of the reaction shown?

What is the activation energy of the reaction shown?