CHEM 1251 Exam #1 Study Guide

exact number

number derived by counting or by definition

example: number of seats in your classroom

- number of millimeters in a cubic centimeter

not exact numbers

any instrument that has a finite certainty

example: the average height of a NBA basketball player

- temperature of the North Pole

- mass of a posted stamp

intensive properties

a physical property that remains the same no matter how much of a substance is present

examples:

-density

-color

-something that begins to melt at 1000 degrees celsius

extensive properties

depend on the amount of matter that is present ex. volume, mass, and the amount of energy

You are given a sample resembling copper. Which of the following properties could be used to help determine whether the sample is really copper?

1. density of the sample

2. melting point of the sample

Pure Substance

A sample of matter, either a single element or a single compound, that has definite chemical and physical properties

Mixture

A combination of two or more substances that are not chemically combined

Compound

A substance made up of atoms of two or more different elements joined by chemical bonds

element

A substance that cannot be broken down into simpler substances

heterogeneous

composed of unlike parts; different; diverse

homogeneous

of the same kind

Scientific Laws

describe how nature behaves

- often referred to as principles

- a brief statement that summarizes past observations and predicts future ones

4 part of the atomic theory

1. each element is composed of tiny, indestructible particles called atoms

2. all atoms of a given element have the same mass dn other properties that distinguid the from the atoms of their elements

3. atoms combine in simple, whole- number ratios to form compounds

4. atoms of one element cannot change into atoms of another element in a chemical reaction, atoms only change the way they are bound together with other atoms.

1st law the paved the way of atomic theory

The law of conservation of mass

law of consolations of mass

in a chemical reaction, matter is neither created or destroyed

2nd law that paved the way of atomic theory

The law of definite proportion

law of define proportion

all samples of a given compound, regardless of their source, have the same proportions of their constituent elements.

Rutheford's Gold Foil Experiment

Fired alpha particles at a thin sheet of gold foil

Most particles passed through

Some particles were deflected

Conclusion: atoms contain a small dense positively core surrounded by mostly empty space

and that in atoms, there are both positively charged and negatively charged particles

3 different types of radiation

alpha, beta, gamma

Milkan's Oil Drop Experiment

deduced the charge of a single electron

- he reasoned that, since each drop must contain an integral number of electrons, the charge of each drop must be a whole number multiple of the electrons charge

nuclear theory of an atom

1. Most of the atom's mass and all of its positive charge are contained in a small cores called a nucleus

2. Most of the volume of the atom is empty space, throughout which negatively charged electrons are dispersed.

3. There are as many negatively charged electrons outside the nucleus as there are positively charged particles (protons) within the nucleus, so the the atom is electronically neutral

mass spectrometry

experimental method of determining the precise mass relative abundance of isotopes in a given sample using an instrument called this.

Schrodinger Cat

demonstrates how quantum strangeness does not transfer to the macroscopic world

on an atomic level, what differences exist between heavier atoms and lighter atoms?

there are multiple differenced but one of the more relevant answers that there are fewer # of protons and, usually, neutrons for the lighter atoms

nuclide representation

shows mass number (upper left), atomic number (lower left), chemical symbol (center), and charge, including sign (upper right), for any individual atom or iron.

ground state

The lowest energy state of an atom

excited state

an electron can transition from a lower energy level to a higher level

absorption

absorbing the quantity of energy

emission

quantum energy released as a photon that exactly matches the energy difference

Mark all of the following statements that are TRUE of density.

1. Density is the ratio of mass to volume

2. Density is a property that depends on temperature.

3. Density is a physical property of a substance.

4.Density can be used to identify substances.

5. Density is an intensive property of matter.