7.01 Endothermic and Exothermic
Driving Question: How are energy transfers during chemical reactions explained and represented by potential diagrams?
Key Ideas and Terms
FQ: What is the relationship between heat, temperature, and thermal energy within a system?
What is thermochemistry?
What is a system?
What are some examples of systems?
The energy of a system is described in terms of temperature, thermal energy, and heat. Describe each of these factors.
· Thermal energy
How does heat flow?
Heat flows spontaneously from matter at a ________ temperature to matter at a _______ temperature.
What controls energy flow?
Energy flow depends on the ________ difference between substances, not on the difference in total thermal energy of the two substances.
This flow of thermal energy will continue until both substances are at the same ________________.
What are the heat and thermal energy units of measurement?
FQ: How does enthalpy change in endothermic and exothermic reactions?
What symbol is used to denote heat?
What is enthalpy?
· Chemists use enthalpy instead of heat to describe the energy transfer. Why?
· What equation is used to represent enthalpy?
When heat flows into matter, what happens?
When heat flows out of matter, what happens?
Explain the difference between reactions that increase in energy and those that decrease in energy.
Reactions that _______ energy from their surroundings, resulting in a net ________ in energy and +q, are called ______________.
Reactions in which there is a ________ of energy to the surroundings, resulting in a net _________ and −q, are called ______________.
The amount of energy absorbed by an endothermic reaction depends on what factors?
List examples of endothermic reactions.
The amount of energy released by an exothermic reaction depends on what factors?
List examples of exothermic reactions.
What controls changes in enthalpy?
The change of enthalpy (△H) in a system is equal to the heat ________ or _______ between the system and its surroundings under constant _________.
When heat is gained in a system, q is _________. When heat is lost from a system, q is __________.
FQ: How do potential energy diagrams represent energy transfers in chemical reactions?
Video: Enthalpy and Reactions
· What causes a negative change in enthalpy?
In an _________reaction, the enthalpy of the reactants, what you begin with, is ___________ than the enthalpy of the products, what you end up with.
· Describe the exothermic reaction demonstration in the video.
· What causes a positive change in enthalpy?
In an ____________ reaction, the reactants have _______ enthalpy than the products. In this case, it takes enthalpy to ______ chemical bonds.
· Describe the endothermic reaction demonstration in the video.
What is a potential energy diagram?
How do potential energy diagrams differ between endothermic and exothermic reactions?
Compare the slope of the line on a potential energy diagram for an endothermic reaction and an exothermic reaction.
FQ: How does activation energy affect the outcome of chemical reactions?
What is activation energy and why is it needed?
Video: Activation Energy
· What do colliding particles need for a successful chemical reaction to occur?
· What unit of measurement is used for activation energy?
· How can the kinetic energy of particles be increased?
· When is the maximum potential energy is reached in particles?
How is activation energy represented on a potential energy diagram?
On a potential energy diagram, the activation energy is represented by the positive _______, or _____, that follows the reactants.
What is required for a reaction to occur?
For a reaction to occur, enough ________ must be provided to the system to meet the ______________ requirement.
Be sure to record any extra helpful notes, vocabulary terms, and practice sample problems.