Chemistry Midterm #1

Hypothesis

a testable statement explaining your data and observations; may be little more than a hunch or guess based upon limited data.

Theory

a tested hypothesis that explains a body of facts; stood the test of time and is supported by a large amount of data.

Law

Observations generally accepted to be true and universal often taking the form of a mathematical equation.

Directly Proportional

two variables if increasing one value causes the other one to increase, or decreasing one value causes the other one to decrease

Indirectly Proportional

two variables if increasing one value causes the other to decrease, or decreasing one value causes the other to increase

Antoine Lavoisier

creator of the Law of Conservation of Mass

Joseph Proust

created the Law of Definite Composition

Atom

the smallest unit of matter; combine to form molecules

Molecule

consist of the same type of atoms or different types of atoms

Compounds

substances containing at least two different elements chemically combined in definite proportions

Mixtures

consist of more than one atom, element, or compound physically bound together

Solid

the state of any matter that has a definite shape and a definite volume

Liquid

the state of any matter that has a definite volume but an indefinite shape

Gas

the state of matter that has neither a definite shape nor a definite volume

Physical Properties

properties that can be observed or measured without altering the identity of the material

Chemical Properties

the ability of a substance to undergo a change that alters its identity

Extensive Physical Properties

depend on the amount of matter present and include mass, length, and volume

Intensive Physical Properties

do NOT depend on the amount of matter present and include melting point, boiling point, density, ductility, malleability, color, crystalline shape, refractive index, etc

Mole

an SI base unit and the measure of the amount of a substance (how many) not how much (mass)

Avogadro’s Number

the larger number a mole refers to; 6.02 × 10^23

Homogenous Mixture

mixture that is uniform throughout

Heterogeneous Mixture

mixture that is not uniform throughout

Solutions

-do not separate on standing

-cannot be separated by filtration

-do not scatter light

-ex: salt water, sugar water, brass, alloys, air, soda, etc

Colloids

-do not separate on standing

-cannot be separated by filtration

-scatter light, exhibit the Tyndall effect

-ex: butter, milk, cream, fog, smog, smoke, asphalt, inks, paints, glues

Suspensions

-settle out on standing

-can be separated by filtration

-may scatter light (usually do not) but are not transparent

-ex: mud, flour in water, sand in water, blood, and most aerosol sprays

Metals

-lustrous &good conductors

-relative high density

-high melting point

-ductile & malleable

-solid at room temp

-high tensile strength

-good reflectors

-crystalline structure

-easily lose electrons & form cations

-corrode easily

Nonmetals

-non lustrous and poor conductors

-brittle

-low density and melting point

-most are solid at room temp, some are gasses & Bromine is a liquid

-tend to gain electrons forming anions

Metalloids

-solid at room temp

-can be shiny or dull

-may be ductile or malleable

-semi conductors

-can act as a metal or nonmetal depending upon what they are reacting with in the chemical reaction

Kinetic Energy

the energy of an object in motion

Potential Energy

the energy of an object due to its position or composition

Law of Conservation of Energy

energy can neither be created nor destroyed in ordinary chemical or physical changes, but can be converted from one form to another

Reactants

substances that exist before the chemical change begins

Products

new substance or substances produced as a result of a chemical reaction

Exothermic

chemical reaction (or physical change) that releases heat

Endothermic

chemical reactions (or physical change) that absorb energy

Activation Energy

initial input of energy required to get a reaction going

Fahrenheit to Celcius

(F - 32)/1.8

Celcius to Kelvin

C + 273

Specific Heat

the amount of heat required to raise the temperature of 1g of a substance 1 degree C; it is an intensive physical property and varies for each substance

Joule

the SI unit of heat energy and all other forms of energy

calorie

non SI unit of energy defined as the amount of heat required to raise the temperature of 1 g of water one degree centigrade

Calorie (food)

= 1,000 cal