Chemistry review (for whenever <3)

Precision

How close measurements are to each other or how repeatable they are.

Accuracy

How close measurements are to an accepted or actual value.

Significant Figure Rules

Non zeroes- Always significant (Ex.- 77)

Sandwich zeroes- Always significant (Ex.- 7007)

Leading zeroes- Never significant (Ex.- 0.07)

Trailing zeroes- Significant with a decimal (Ex.- 70.0 has 3 sig figs, 70 has 1)

Solids

Have a definite shape and a definite volume

Liquids

Have an indefinite shape and a definite volume

Gases

Have an indefinite shape and an indefinite volume

Ways to tell a chemical change has occurred

Change in color, odor produced, temperature change, gas/ bubbles produced

Filtration

Separates solids from liquids by using a porous barrier, like sand and water

Distillation

Separates substances on the basis of the boiling points of the substances like alcohol and water

Centrifugation

Separates by spinning a sample very rapidly, like water and precipitate

Chromatography

Separates substances based on their movement through a special paper, like ink

Intensive property

A physical property that can be used to identify an unknown substance (Ex.- density, conductivity, color, melting point, solubility)

Extensive property

A physical property that can NOT be used to identify an unknown substance (Ex.- length, volume, mass)

Element

A substance that can NOT be separated into simpler substances by physical or chemical means (Ex.- Oxygen)

Compound

A chemical combination of two or more different elements (Ex.- H2O)

Solute (give example)

The substance doing the dissolving (Ex.- water in sparkling water/soda)

Solvent (give example)

The substance doing the dissolving (Ex.- water in sparkling water/soda)

Density formula

Mass divided by volume

Random errors (how do you reduce them?)

Accurate, but not precise; you can reduce these errors by changing your methods of testing

Systemic errors (how do you reduce them?)

Precise, but not accurate; you can reduce these errors by replacing the equipment/tools you use

Endothermic (which phase changes are an example of this?)

A process that absorbs energy from the surroundings (includes melting and evaporating)

Exothermic (which phase changes are an example of this?)

A process that releases energy into the surroundings (includes freezing and condensation)