Kinetic Particle Theory

Physical Change

1. No new substance formed
2. Usually easily reversible
3. May/may not involve heating

Chemical Change

1. New chemical is/are formed
2. Usually irreversible ( only under special conditions )
3. Heat energy may be given off/absorbed
4. Light energy may be given off/absorbed

Signs of a Chemical Change

1. a change in colour
2. production of a gas
3. formation of a precipitate from mixing solutions
4. Change of temperature ( all the above must follow the formation of a new chemical substance ).

Process when new chemical substances are formed

1. reactants -> products 

• New chemical substances formed due to rearrangement of atoms
• No atoms are created/destroyed, according to the Law of Constant Mass

Types of Chemical Reactions

Combination (Synthesis)

• two or more substances combined to form a new substance
• magnesium + oxygen -> magnesium oxide

Decomposition

• substance breaks down 2 or more simpler substances
• calcium carbonate -> calcium oxide + carbon dioxide

Combustion / Burning

• combination of a substance with oxgen
• heat and light energy are given off
• hydrocarbon + oxygen -> carbon dioxide + water

Displacement Reaction

• a chemical reaction with an atom/a group of atoms get replaced by another atom/group of atoms
• hydrogen bromide + chlorine -> hyydrogen chloride + bromine

Definition:
States that all matter is made up of tiny particles and that these particles are in constant random motion.

Assumptions:

• All matter is made up of tiny particles.
• The tiny particles are in constant random motion.
• These particles in motion have kinectic energy.
• Higher the temperature, the faster the movement of these particles.

Melting

• Solid particles gain energy when heated
• particles vibrate faster
• as temperature increases, vibrations also increase
• finally, particles are able to overcome the forces that hold them in their fixed positions