endothermic and exothermic reactions Flashcards
(16 cards)
What is the Law of Conservation of Energy?
Energy cannot be created or destroyed, only transformed from one form to another.
What does the Law of Conservation of Energy imply about energy in a system?
The total amount of energy in a system is always constant.
What happens when the energy in a system falls?
There will be a corresponding rise in the energy of the system’s surroundings.
What happens when the energy in a system rises?
There will be a corresponding fall in the energy of the system’s surroundings.
What is enthalpy?
The total energy present in a substance.
What types of energy are included in enthalpy?
Energy stored in chemical bonds (chemical potential energy) and the energy due to particle motion (kinetic energy).
What does enthalpy change represent?
The heat gain or loss of the system equals its change in enthalpy for chemical changes at constant pressure.
What occurs during chemical reactions in terms of energy?
Chemical bonds in reactants are broken and new bonds are created, resulting in a change in potential energy.
How does energy conservation relate to temperature changes in systems?
Any change in chemical potential energy must be balanced by an opposite change in another form of energy, usually kinetic energy (heat).
What happens to the temperature of a system when it absorbs heat?
The temperature of the system will rise, causing heat energy to flow into the surroundings.
What are exothermic reactions?
Reactions that lose heat to the surroundings, raising the system’s temperature.
What happens to enthalpy in exothermic reactions?
Enthalpy decreases because heat is lost from the system to the surroundings.
What are endothermic reactions?
Reactions that absorb heat from the surroundings, lowering the system’s temperature.
What happens to enthalpy in endothermic reactions?
Enthalpy increases because heat is gained by the system from the surroundings.
What occurs during bond breaking?
Absorption of energy (endothermic reaction) raises enthalpy.
raising enthalpy means a positive enthalpy
What occurs during bond making?
Releases energy (exothermic reaction) and lowers enthalpy.
lowering enthalpy means a negative enthalpy
