Structure of Matter

The smallest unit of matter is the atom. Atoms consist of a nucleus with protons and neutrons, surrounded by a field of electrons. Individual atoms are all one of the elements of the periodic table. Atoms of elements group together to form molecules of compounds.

States of Matter

Matter can take the form of a solid, liquid, gas or plasma. States change when the temperature changes. As states of matter change from cold to hot, molecules get further apart and move around more easily. Matter also becomes less dense.


Density is the amount of mass a substance has per its volume (D=m/V). In liquid or gas form, less dense substances float on top of more dense substances.

Chemical Reactions

Chemical reactions are when two or more substances come into contact and their molecular structure is changed to create new substances. Chemicals and their reactions are written using chemical abbreviations.

Conservation of Mass

In a chemical reaction, the mass of the individual elements involved does not change. Nothing is wasted and nothing new appears, though some energy may be given off. This is called the law of conservation of mass.

Chemical Equations

Chemical equations are written using abbreviations for the elements and molecules involved. Take this example: 2HCl + 2Na -> 2NaCl + H2. In this reaction, two molecules of hydrogen chloride (shown as HCl, meaning each molecule has one atom of hydrogen, H, and one of chlorine) reacts with two molecules of sodium (Na) to form 2 molecules of sodium chloride (or salt, NaCl) and a molecule containing two atoms of hydrogen (H). The same number of Chlorine, Sodium and Hydrogen atoms exist on each side of the equation.


Solubility is the ability for a substance (the solute) to dissolve into another substance (the solvent). Once dissolved a solution is formed. Increasing the heat of the solvent allows more of the solute to dissolve. For example, if you want to dissolve sugar in tea, more sugar will dissolve if the tea is hot.


Saturation occurs when a solution has the maximum amount of solute dissolved in it.



Tea Photo:  Nate Steiner