Chem Exam 1

Chemistry

study of matter and its properties and the changes it undergoes

Matter

anything that has mass and takes up space

Intensive properties

independent of the amount present, ex: boiling point, color, temperature

Extensive properties

depend on amount present, ex: mass, size, volume

Ratio of 2 extensive properties

becomes an intensive property, ex: density

Physical Changes

do not change substance, ex: crushing can, melting ice, boiling water, shredding paper

Chemical Changes

result in new substance, ex: iron rusting, burning wood, cooking egg

Energy

capacity to do work or transfer heat, makes other things happen

Work

transfer of energy when a force is exerted on an object that causes displacement, we use energy to push

Heat

flow of energy that causes temperature of object to increase, exchange of energy between 2 things at different temperatures

Force

any push or pull on an object

Kinetic energy

energy of motion, magnitude depends on objects mass and velocity

Potential Energy

depends on relative position compared to other objects (stored energy)

Precicion

how clustered measurements are

Accuracy

how close experimental values are to exact

Law of conservation of mass

total mass present at the end of a reaction is the same as the start

1st postulate of atomic theory

each element is composed of atoms

2nd postulate of atomic theory

all atoms of a given element are identical to one another (wrong), but the atoms of one elment are different from the atoms of all other elements

3rd postulate of atomic theory

atoms of another element are not changed into atoms of a different element by chemical rxns, atoms are neither created nor destroyed in chemical rxns

4th postulate of atomic theory

atoms of more than one element combine to form compounds, always have same relative number and kind of atoms

cathode rays

-discovery of electrons

-JJ Thompson

-gave charge to mass ratio of electrons

Millikan oil drop

gave charge of electrons

Radioactiviity

spontaneous emission of high energy radiation by an atom, showed that there are more particles in the subatomic area

Types of radiation

alpha (positive), beta (negative), gamma (uncharged)

Plum pudding model

wrong

• JJ thompson

• said positive spread throughout and negative electrons were embedded

Rutherford and discovery of nucleus

• rutherford alpha particles at gold foil

• notied small fraction of alpha particles scattered at large angles because of the nucleus

Physical Properties

can be observed without changing identity and compositon of substance, ex: color, odor, density, and composition

Chemical properties

describe the way a substance may react to form others, ex: mass and volume

Heterogenous mixtures

do not have same composition, properties, and appearance, ex: wood

Homogenous mixtures

uniform throughout, also called solutions, can be solids, liquids, and gasses

What did rutherford initially expect would happen with the gold foil

that the molecules would pass through largely undeflected becasue they didnt know about the nucleus yet

Groups

vertical, show how element will react

Periods

Horizontal

Molecular compound

has particular molecules

Ionic compound

infinite lattices

Diatomic Molecules

from N to I in L shape

dichromate

Cr₂O₇^2-

acetate

C₂H₃O₂^-

Ide

hydro ic

ate

ic

ite

ous

Strong Nuclear Force

very strong at short distances, holds positive charges together in nucleus

Nuclear Model

most of mass resides in small dense nucleus

majority of atom empty space

Metals

on left

nonmetals

on right

metalloids

makeup all semiconductors, sometimes act as metal or nonmetal

Permanganate

MnO4^-

Law of conservation of mass

comes from third postulate, says total mass is the same at the beginning and end of a reaction

Law of constant composition

compounds have definite composition

comes from fourth postulate

Law of multiple proportions

ratio of masses in compound is in whole numbers

Electromagnetic Forces

attractive between opposites, repulsive between same

Metalloids

boron to tellurium staircase

Hydrogen

Nonmetal

Gamma Rays

dont have mass