Elements, Compouds, Mixtures, Bonds, & Physical/Chemical Changes

Element

A pure substance made of only one type of atom. (Ex. Carbon (C), Iron (Fe))

Compound

A pure substance made of 2+ different elements chemically combined in fixed ratios. (Ex. NaCl, H20)

Can compounds be broken down by physical changes?

No, only chemical changes.

Mixture

A physical combination of 2+ substances, can be separated physically.

Types of mixtures

Homogeneous (uniform)(solutions) and Heterogeneous (non-uniform).

Example of a homogeneous mixture

Salt water, air.

Example of a heterogeneous mixture

Salad, trail mix.

Ionic bond

Transfer of electrons to form ions, made of nonmetal and metal

Properties of ionic bonds

High melting/boiling point, conduct electricity when dissolved, tends to be brittle solids

Molecular covalent bond

Electrons shared in small molecules, made entirely of nonmetal atoms

Properties of molecular covalent bonds

don't conduct electricity, some dissolve in water, can be solids, liquids, or gases

Metallic bond

Atoms share a "sea of electrons." (move freely throughout material), made entirely of metal atoms

Properties of metallic bonds

Conductors, shiny, malleable, bendable, dont dissolve in water

Network covalent bond

Atoms bonded in a giant 3D network, made of nonmetal and silicon

Properties of network covalent bonds

Very hard solids, don't conduct (except graphite), dont dissolve, not flexible or bendable

Polymers

Long chains of repeating molecules, made entirely of nonmetals (subtype of molecular covalent)

Physical change

A change in form/appearance, no new substance

Examples of physical change

Melting, boiling, dissolving, tearing.

Chemical change

A change that creates a new substance.

Signs of a chemical change

Gas bubbles, color change, temperature change, burning, rusting.