Chemistry is the science of composition, structure, and changes in matter. Matter is anything that takes occupies space and has volume, and a weight or mass (even gases like air have a tiny weight). That which is not matter is a vacuum. Matter is built out of elements. All chemical elements are categorized in the periodic table - a table which organizes the periodic occurence of chemicals (every second-ish chemical is a gas, etc.) into columns and rows. A unit of element - the smallest unit that retains the properties of the matter - is an atom.

Periodic Table

Substance categories:

                 Physical changes                
####### sublimation  ##### condensation  ######## 
#SOLID# ---------->  #GAS# ----------->  #LIQUID#
####### <----------  #####  <-----------  ########
  ^V     deposition        evaporation.    ^V        
  ||                                      ||        
  ||               melting                ||        

Substances can be further categorised based on their

The smallest building blocks in chemistry are atoms. An atom consists of a core/nucleus (made of protons and neutrons), an outer shell with electrons. A group of 2 or more atoms forms a bond, which holds some chemical element. Bonds form chemical compounds. Protons and neutrons can be split into quarks.

Atoms have three shells - the first capable of holding 2 electrons, second and third 8. The most outer shell with electrons on it currently is the valence shell. Atoms wish to remain stable by having the exact maximum number of electrons on this shell. When they do not have the correct number, they try to form molecules by sharing electrons. Those atoms that already have their valence shell filled with electrons do not want to form bonds with other elements. They are noble gasses. Elements can be noted using the Dot Structure:

.   .     ..    .  
H  .C.   :Ne:   Mg.
    .     ..       


Solution - substance (solute) distilled in water or similar liquid (solvent), can be concentrated (high concentration), dilute (low concentration). Certain chemicals react better in a solvent. Concentration measured in moles (M). moles of solute / liters of solution = molarity. Standalone mole noted as mol.

Non-chemical changes of matter

Mixture - if two substances are put together, but no chemical change happens, e.g. rocks + water. Dissolving is a process in which in a mixture, one substance breaks down to fit with the other substance, e.g. salt + water. A heterogenous mixture is uniform; a homogenous is non-uniform - samples of different segments yield different results, e.g. sands with dirt on top.

Distillation - separation of mixtures, e.g. heating salted water and separating evaporated water from salt.

Filtration - putting substance through filter to separate heavy/large/solid molecules from liquid/small


Every particle has energy. They like to go from a high-energy to a low-energy state. Measured in Joules (J).


Concentration of hydrogen in a water solution. Measured in pH. Salting things makes them less acidic, adding lime makes more acidic.
A subset of chemical materials which is known for their high conductiveness of heat and electricity.