Chapter 1 Review: Energy and Reaction Rate ✓
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What is energy?
Energy is the capacity to do work or cause change
What is energy measured in?
Joules (J)
What are some forms of energy?
-Heat -Chemical -Electrical -Light -Kinetic -Potential
What is a system?
The reaction mixture
What is the surroundings?
The object holding the mixture and anything else around it
What is the Law of Conservation?
Energy is neither created nor destroyed. Energy changes from one form of energy into another form
What is enthalpy?
A measure of the energy present in a substance
What happens during a chemical change in terms of the bonds?
Some bonds are broken and new ones are formed which causes a change in the amount of stored chemical potential energy
What is enthalpy change?
The amount of heat energy transferred during a chemical reaction at constant pressure
How to find enthalpy change?
enthalpy of products - enthalpy of reactants
What is an exothermic reaction and give an example of one.
Reactions that lose heat to the surroundings (e.g. combustion
Is the value of enthalpy change negative or positive for an exothermic reaction?
Negative because enthalpy decreases during the course of the reaction
Why do exothermic systems feel hot?
Exothermic systems feel hot because energy is released to the surroundings as bonds form. This causes a decrease in enthalpy (chemical potential energy), as some of the chemical potential energy stored in bonds is converted into particle kinetic energy. The increase in particle kinetic energy leads to a rise in the system’s temperature, making it feel hot.
What is chemical potential energy?
The energy stored in the chemical bonds of a substance
How is chemical potential energy released?
Through a chemical reaction
What is kinetic energy?
A form of energy that an object or a particle has by reason of its motion
What are endothermic reactions and give an example of one.
They are reactions that gain heat from the surroundings (e.g. ice melting)
Is the value of enthalpy change negative or positive for an enothermic reaction?
Positive because enthalpy increases during the course of the reaction
Why do endothermic systems feel cold?
Endothermic systems feel cold because energy is absorbed from the surroundings to break bonds. This causes an increase in enthalpy (chemical potential energy) as some of the kinetic energy of the particles is converted into potential energy stored in bonds. The decrease in particle kinetic energy leads to a lower temperature in the reacting system, making it feel cold.
What is an energy profile diagram?
An energy profile is a representation of a chemical reaction as a single energetic pathway as the reactants are transformed into products.
Draw a exothermic energy profile diagram with these labels: -Products -Reactants -Enthalpy change -Transition state -Activation energy
Answers on page 4
Draw a endothermic energy profile diagram with these labels: -Products -Reactants -Enthalpy change -Transition state -Activation energy
Answers on page 4
Is enthalpy change written with the products or reactant for exothermic reactions
With the products because heat is being released
Is enthalpy change written with the products or reactant for endothermic reactions
With the reactants because heat is being absorbed