Chem

Matter - a substance that has volume (occupies space) and has a mass.
All matter are made up of atoms which bond together to produce different substances

Atom (classic definition): Building block of matter

1802 - first atomic theory of matter was presented by John Dalton. Dalton proposed that all matter is made up of tiny spherical particles, which are indivisible and indestructible.

We now know it is incorrect and atoms are in fact made of smaller subatomic particles (protons, neutrons and electrons)

Matter can be split into two groups: pure substances and mixtures.

Pure Substances

A pure substance is a substance made up of only one type of particle throughout. This causes it to have a fixed composition and consistent properties. The particles can either be made from a single element, or multiple elements, but every one must be the same.

e.g.

- A copper wire is a pure substance as it is comprised entirely of copper atoms.

- Carbon dioxide gas is a pure substance as it is comprised entirely of carbon dioxide molecules (CO2).

A pure substance cannot be separated by a physical process (e.g. filtration).

Mixtures

Mixtures consist of two or more different types of particles that are not chemically combined together. These particles can be elements, compounds, or both.

e.g.

- Air is made up of oxygen gas (O2) and nitrogen gas (N2), as well as trace amounts of other gasses, such as carbon dioxide gas (CO2).

- Salad dressing is made up of vegetable oil and vinegar

Mixtures can be separated by a physical process (e.g. filtration)

Elements

Elements are types of atoms that all share the same number of protons. For example, an atom with one proton is always a hydrogen atom, and an atom with 8 protons is always an oxygen atom. There are about 118 known elements, and each one has its own unique characteristics. The periodic table of elements lists all of the different elements that have been discovered, and each elements has a unique name and symbol.

In nature, some elements prefer to exist in a monatomic form (i.e. individual atoms). Other elements prefer to form into a polyatomic form (i.e. molecules). Regardless of its preferred arrangement, an element can also be considered a pure substance, because, if you have multiple particles, they will all be the same.

Reminder: Molecules are two or more atoms that are held together by chemical bonds.

Elements cannot be separated into simpler substance by physical or chemical means.

Compounds

A compound is a substance that is made up of two or more different elements, chemically bonded together. If they aren’t mixed with anything else, compounds can also be considered a pure substance (although not all pure substances are compounds).

To determine whether a pure substance is an element or a compound, you must determine if the substance can be broken down into simpler substances.