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Bond Energy
The energy change associated with breaking or forming chemical bonds.
Reaction Rate
The speed at which reactant concentrations change in a chemical reaction, often measured in terms of time.
Reactants
Substances present before a chemical reaction occurs.
Products
Substances that are formed as a result of a chemical reaction.
Collision Frequency
How often reactant particles collide, which affects the reaction rate.
Surface Area
The amount of exposed area of a substance; increasing surface area can increase reaction rate.
Concentration
The amount of reactant particles present, increasing concentration generally increases the reaction rate.
Temperature
A measure of the average kinetic energy of particles; higher temperatures usually increase reaction rates.
Catalyst
A substance that increases the reaction rate without being consumed by lowering activation energy.
Heat
Energy transferred between samples of matter due to a temperature difference.
Thermal Equilibrium
A state reached when two substances at different temperatures end up at the same temperature.
Specific Heat
The amount of heat required to raise the temperature of 1 gram of a substance by 1 °C.
Calorimeter
An apparatus used to measure the amount of heat involved in a chemical reaction by measuring temperature changes.
Bond Enthalpy (ΔH)
The energy change for breaking a particular bond; can be positive or negative based on whether heat is absorbed or released.
Endothermic Reactions
Reactions that absorb energy, having products with more energy than the reactants.
Exothermic Reactions
Reactions that release energy, having products with less energy than the reactants.
Activation Energy
The minimum energy required to initiate a chemical reaction; all chemical reactions require this.
Lattice Energy
The energy required to separate one mole of an ionic compound into its ions.
Increases as the charges of ions increase, Increases as the radii of ions decrease.
Greater lattice energy means a stronger chemical bond.
Hess’s Law
The principle stating that the total enthalpy change for a reaction is the sum of the enthalpy changes for individual steps.
Enthalpy is the same magnitude, but flip sign for reverse reactions.
Reaction Mechanism
The series of steps that describe the pathway from reactants to products in a chemical reaction.
What are the factors that affect reaction rate?
Increasing surface area increases rate
Increasing concentration increases rate
Adding a catalyst increases rate
Increasing temperature increases speed = increased rate
Reaction Rate
Reaction rate depends on collision frequency,
energy, and the orientation of molecule
Does a material that takes a long time to cool and to heat up have a high or low specific heat?
High
Specific Heat Equation
q = m c ΔT
○ q is heat (J or kJ)
○ m is mass (g, kg, mg, etc.)
○ c is specific heat (J/g°C)
○ ΔT is temp change (°C or K)
How do you determine the enthalpy of a reaction?
ΔH = Bonds Broken – Bonds Formed
