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Thermochemistry - Coggle Diagram
Thermochemistry
What is it?
The study of the heat energy
The relation between chemical reactions and heat
Measuring Changes
Heat
Symbol: "q"
Is thermal energy
It is tranferred from a hotter system to a cooler system that are in contact
It is a process
Temperature
Is a measure of the average kinetic energy of the atoms or molecules in the system
It is the measure of the amount of energy of a certain object
An instrument is required
Thermometer
Enthalpy
What is it?
The decrease or increase of energy in a chemical reaction
The amount of energy a reaction can lose or gain to become a product
Energy transferred to a reaction
Types of reactions
Endothermic reactions
The system takes heat energy from the surroundings
Environment gets cooler
They need energy to react
Enthalpy changes will ALWAYS be positive
Increase of enthalpy in the reaction
Total energy of products = total energy of reactants + heat taken in
The products have high energy and are less stable than the reactants
Exothermic reactions
The heat energy is transferred from the system to the surroundings
The surroundings get hotter
There are 2 parts of the reaction
Initial state
Reactant
Final state
Product
The product has less energy than the reactant
Before the reaction it wasn't stable
It lowers the energy to gain stability
Enthalpy changes will ALWAYS be negative
Total energy of the reactants= total energy of the products + heat given out
Enthalpy cannot be measured, but the changes can
Enthalpy changes
Symbol: "∆H"
We can't know how much energy can be released or gained
Symbol "H"
Systems and Surroundings
System
Chemical reaction that is taking place
Surroundings
Everything else in the universe
Internal Energy
Where does energy come from?
Is the energy associated with the random, disordered motion of molecules
When an object is moving by itself, energy is created
Inside the object, molecules are bonded and bonds always move
Bonds can be
Moved
Causing internal energy
Rocked
Stretched
Invisible microscopic energy on the atomic and molecular scale
Example: a glass of water sitting on a table
It has no apparent energy on a macroscopic scale, but on a microscopic scale there is kinetic and potential energy
When an object has to be moved not by itself, it is not internal energy
This is called external/ macroscopic energy
It is separated in scale from the macroscopic ordered energy associated with moving objects
Examples
Polyatomic gases
Rotational and vibrational kinetic energy
Ideal monoatomic gas
Transitional kinetic energy
Linear motion of the "hard sphere"
When an atom is far away from another atom
Liquids and solids
Potential energy associated with the intermolecular attractive forces
It is composed of two types of energy
Kinetic Energy
Bond
Energy inside and object
Vibration and rotation
Transational
Movement from one place to another
Potential Energy
Attraction between particles in a molecule
Intermolecular forces
Interruption between molecules
It has a microscopic energy
There are three types
London forces
They are basic forces that happen in all molecules
They explain interaction between non-polar molecules
Spontaneous polarization of molecules
Dipole-dipole forces
Attraction and repulsion between polar molecules
These forces are stronger than London forces
Dipole: 2 poles
Hydrogen Bonds
Also called hydrogen bridges
Bonding between hydrogen and an electronegative element
They are a type of dipole-dipole interaction
Between the molecules that have a hydrogen atom and a very electronegative atom like Oxygen, Fluorine or Nitrogen
Specific heat
Energy required to increase in 1 degree the temperature of 1 gram of substance
Depends on the internal energy each substance has
