Chem 1 Exam 1

Pure substance

material w/ strong composition + uniform structure

Mixture

physical combo of 2 or more substances that are not chemically bonded

Element

pure substance made of only 1 type of atom

Compound

pure substance made of 2 or more elements chemically bonded in a fixed ratio

Homogenous vs. Heterogeneous

Homo = Uniform throughout

Solution

type of homogenous mixture where 1 substance is dissolved in another

Physical Property

Can be observed or measured w/o changing substance’s identity

Chemical Property

A characteristic that describes a substance’s ability to change into a new substance

Intensive Property

D/n depend on amount of matter (boiling point, density, color)

Extensive Property

depends on amount of matter (mass, volume, length)

Examples of physical changes

boiling water, dissolving sugar in water, melting ice

Examples of chem changes

rusting iron, burning wood, baking a cake

Hypothesis

Predicts: If I do X, then X will happen

Theory

Explains based on lots of evidence: cell theory

Law

Describes: Law of Conservation of Mass

Length, mass, temp, time, volume

meters, grams, celsius, seconds, mL

Precision

How close the measurements are to each other

Accuracy

How close the measurements are to the true value

Law of conservation of mass

matter c/n be created nor destroyed

Law of Definite Proportions

a compound always contains the same proportion of elements by mass

Law of Multiple Proportions

an element may combine in different ratios w/ another element to form different compounds

Dalton’s atomic theory of matter

1.) Matter made up of atoms

2.) Mass of atom of 1 element is different from mass of an atom of any other element

3.) atoms combine in whole # ratios to form molecules

Ion = net electric charge due to loss or gain of an electron

cations lose electrons, while anions gain electrons

Atomic #

protons in an atom’s nucleus

Mass #

protons + neutrons in an atom’s nucleus

Atomic mass

average mass of all isotopes of an element (weighed by abundance)

Isotope

Atoms of the same element (came # of protons) but different # of neutrons