Unit 3 Chemistry

i better not fail

Thermochemistry

Study of changes involved in chemical reactions, changes can be physical, chemical or nuclear

All energy transformations can be governed by the first law of thermodynamics, which states":

The total energy in the universe is a constant

Euniverse = Esystem + Esurroundings

Esystem = -ΔEsurroundings 

Thermal energy

Energy avaliable from a substrance as a result of its motion of its molecule

Chemical Systen

Set of reactants and products undergoing energy transformations: can be opened, closed or isolated

Open Chemical System

Energy and matter can move in or out

Closed Chemical Systen

Only energy can move in or out

Isolated Chemical System

Neither energy nor matter can move in or out

Surroundings

All matter around the system that is capable of absorbing or releasing thermal energy

Heat

Amount of energy transferred between substances, systems or surroundings. When a reaction occurs, heat is transferred between substances, systems and surroudings

Exothermic

A chemical system that released energy to the surroundings 

Endothermic

A chemical system that absorbs energy from its surroundings

Temperature

A measure of the average kinetic energy of the particles

The Second Law of Thermodynamics

When two objects are in thermal contact, heat is always transferred from the object at a higher temperature to an object at a lower temperature until the two objects are at the same temperature 

Calorimetry

Experimental technique used to measure heat energy changes in a chemical system

Calorimeter

Instrument for measuring the heat of a reaction 

Three factors: ______, ________ and ______ are combined in an equation to represent the quantity of heat (Q) transferred

mass, temperature and type of substance 

Equation to represent the quantity of heat transferred

Q=mcΔT

Specific Heat Capacity

Amount of energy that is needed to raise the temperature of one gram of the substance by 1 deg Celsius. Unit is J/g o C

Enthalpy

The total internal energy of a substance at a constant pressure (H)

ΔH of a process is equivalent to its _______ at constant pressure

heat change 

ΔH can also be associated with

physical changes, chemical reactions and nuclear changes