Energy and Chemical Change Flashcards
Define the term “Chemical Potential Energy”.
Chemical potential energy is the energy due to the relative position of atoms.
Define the term “Enthalpy”.
The total energy content of a system.
Define the terms “Reactants” and “Products”
Reactants: Substances that take part in a reaction at the beginning.
Products: Substances that are produced at the end of a reaction.
Define the term “Heat of reaction”.
The change in enthalpy during a reaction at constant pressure.
Enthalpy of PRODUCTS - Enthalpy of REACTANTS.
What is Thermodynamics?
Thermodynamics is the study of heat energy flow in chemical and physical processes.
What is the difference between an EXOthermic and an ENDOthermic reaction?
Exothermic: A reaction in which the enthalpy of the products is less than the enthalpy of the reactants - heat energy is released to the surroundings.
Endothermic: A reaction in which the enthalpy of the products is more that the enthalpy of the reactants - heat energy is absorbed from the surroundings.
What type of reaction (endothermic or exothermic) Respiration? Give a similar reaction.
Respiration is exothermic, it’s the same type of reaction that takes place when sugar is ignited.
What type of reaction (endothermic or exothermic) Photosynthesis? Why?
Photosynthesis is an endothermic reaction as heat energy is taken in from the sun.
True or False: If a forward reaction is exothermic, the reverse reaction is also exothermic.
False, if a forward reaction is exothermic, the reverse reaction is always endothermic.
Fill in the blanks:
The energy that is stored as 1.____ energy in 2.______ and other organic compounds can be released by 3.______ as well as by respiration.
- bond
- carbohydrates
- combustion
Define the term “Combustion”.
Combustion is an exothermic chemical reaction of a substance with oxygen.
Define the term “Fuel”.
Fuel is a substance that releases a large amount of energy when it burns or reacts.
(From Worked Example, pg 228)
Explain why Methane provides the most energy per gram.
Methane is a very light gas so there are more molecules in 1g or methane than in 1g of the other fuels. Therefore more collisions are likely to happen and the energy per gram is higher.
