3- Reaction rates and states of matter Flashcards
What is energy?
energy is the ability to do work
Two classifications of energy?
1- Potential energy; result of position, condition, composition (chemical/nuclear)
2- Kinetic energy; because of motion (mechanical/electrical)
What is a reaction rate?
the rate at which reactants are consumed, or products are produced, in a chemical reaction
What determines a reaction rate?
The speed at which reactant(s) is/are used up
The speed at which product(s) is/are formed
eg Reactions which require the breaking of covalent bonds are slow and have higher activation energies. (ionic=faster)
What is activation energy?
the amount of energy required to activate a transformation of reactants to products
What occurs in an exothermic reaction?
energy is released as the reaction occurs
reactants have more energy than the products
What is an endothermic reaction?
energy is required for the reaction to occur (eg photosynthesis)
(Endothermic reactions occur when the energy required to break bonds in the reactants is more than the energy released by the bond formation in the products)
What is a catalyst in a living system?
Enzymes
Name 4 factors that affect the rate of reaction
1- Physical Nature of Reactants
2- Reactant Concentrations
3- Reaction Temperature
4- Presence of Catalysts
How does the physical nature of reactants affect a reaction?
A reaction will occur faster when the reactants are in the same physical state, which includes the physical state of each reactant (s, l, or g) and the particle size.
How do the reactant concentrations affect a reaction?
Reaction rate increases as concentration increases due to an increased rate of collisions
How does the reaction temperature affect a reaction?
A higher temperature provides reactant molecules with more kinetic energy and an increased molecular speed
How does the presence of catalysts affect a reaction?
The presence of catalysts in a reaction lower the activation energy, which creates a more favourable environment for the reaction to occur.
(reaction rate increases)
What is a catalyst?
a substance that increases a chemical reaction rate without being consumed in the chemical reaction
How to catalysts increase reaction rates?
LOWERS THE ACTIVATION ENERGY = increase the reaction rate
What are intermolecular forces responsible for?
Keeping molecules together
the strength of these forces that determine if a substance will be a solid, liquid, or gas
Name 3 types of intermolecular forces
1- Hydrogen bonds (not true chemical bonds)
2- Dipole-dipole attractions
3- Dispersion forces
What are intramolecular forces?
Intramolecular forces are the bonds that hold different molecules to one another, and are referred to as the true chemical bonds.
Name 2 types of intramolecular forces
1- Ionic bonds within ionic compounds
1- Covalent bonds within covalent compounds
What is the strongest type of bond?
Hydrogen bond
Where do hydrogen bonds occur?
Hydrogen bonds occur between polar molecules within a hydrogen-containing molecule: a hydrogen atom with low electronegativity is covalently bonded to a highly electronegative element
What are dipole-dipole attractions?
Attractive forces in polar molecules
eg hydrogen bond
What are dispersion forces?
weak attractions between non-polar molecules that result from momentary uneven electron distributions within the molecules
What are ionic bonds?
strong attractive forces that hold positive and negative ions together.
