CHEM 101 - Exam #1 Study Guide (Ch. 1-3)

chemistry

the study of matter and the changes it undergoes

scientific method

a systematic approach to research

qualitative data

general observations

quantitative data

comprising of numbers obtained by measurement

hypothesis

a tentative explanation for a set of observations

law

a mathematical relationship that is consistently found to be true

theory

a general principle or body of principles that has been developed to explain a wide variety of phenomena (this is NOT a wild guess)

two major goals of science

prediction and control

two "better" goals of science

understanding and explanation

four basic rules of good science

1. results should be reproducible by others

2. detailed research results should be reviewable

3. conclusions should be reasonable and unbiased

4. "give credit when credit is due"

physics

chemistry in motion

biology

chemistry in a cell

engineering

chemistry in application

matter

anything that occupies volume and has mass

matter is governed by...

composition and energy

mixture

a combination of two or more substances in which the substances retain their distinct identities

homogeneous mixture

composition of the mixture is the same throughout

heterogeneous mixture

composition of the mixture is not uniform throughout

mixture separation

physical means can be used to separate a mixture into its pure components

element

a substance that cannot be separated into simpler substances by chemical means

number of elements defined

114

number of elements that naturally occur on earth

82

number of elements been created by scientists

32

compound

a substance composed of atoms of two or more elements chemically united in fixed proportions

compound separation

compounds can only be separated into their pure components (elements) by chemical means

physical property

properties that can be observed and measured without changing the composition of the substance (color, density, conductivity, etc.)

chemical property

properties that are only observable during a chemical change (combustibility, food digestion...)

extensive property

a property that depends upon how much matter is being considered (mass, length, volume)

intensive property

a property that does not depend upon how much matter is being considered (density, temperature, color)

physical change

does not alter the composition or identity of a substance (ice melting, sugar dissolving in water)

chemical change

alters the composition or identity of the substance(s) involved (hydrogen burns in air to form water)

energy

the capacity to do work

radiant energy

energy that comes from the sun and is earth's primary energy source

thermal energy

the energy associated with the random motion of atoms and molecules

chemical energy

the energy stored within the bonds of chemical substances

nuclear energy

the energy stored within the collection of neutrons and protons in the atom

potential energy

the energy available by virtue of an object's position

First Law of Thermodynamics (Law of Conservation of Energy)

energy can be converted from one form to another, but cannot be created or destroyed

two critical parts to every measurement

number and unit

two major parts of each SI unit

base unit and prefix

mass

measures the quantity of matter

weight

the force that gravity exerts on an object

SI unit of mass

kilogram

1 kg = 2.2 lbs

formula for weight

c*mass

- on earth, c = 1.0

- on moon, c ~ 0.1

volume

SI derived unit for volume is cubic meter (m³)

- 1mL = 1cm³

- 1L = 1000mL = 1000cm³ = 1dm³

density

SI derived unit is kg/m³

formulas for density

mass/volume = m/v = kg/m³

- 1g/cm³ = 1g/mL = 1000kg/m³

conversion of Celsius to Kelvin

K = °C + 273.15

conversion of Celsius to Fahrenheit

°F = (9/5) x °C + 32

freezing point

273.15K = 0°C = 32°F

boiling point

373.15K = 100°C = 212°F

pound to Newton ratio

1lb = 4.45N

number of atoms in 12 g of carbon

6.022 x 10²³

Avogadro's Number

6.022 x 10²³

mass of a single carbon atom in grams

1.99 x 10⁻²³

scientific notation rules (addition/subtraction)

1. write each quantity with the same exponent n

2. combine N₁ and N₂

3. the exponent, n, remains the same

scientific notation rules(multiplication)

Multiplication

1. multiply N₁ and N₂

2. add exponents n₁ and n₂

scientific notation rules(division)

Division

1. divide N₁ and N₂

2. subtract exponents n₁ and n₂

roles of sig figs

1. don't talk about Sig Figs...Any digit that is not zero is significant

2. zeros between nonzero digits are significant

3. zeros to the left of the first nonzero digit are not significant

4. if a number is greater than 1, then all zeros to the right of the decimal point are significant

5. if a number is less than 1, then only the zeros that are at the end and in the middle of the number are significant

sig fig rules (addition/subtraction)

the answer cannot have more digits to the right of the decimal point than any of the original numbers

sig fig rules (multiplication/division)

the number of significant figures in the result is set by the original number that has the smallest number of significant figures

accuracy

how close a measurement is to the true value

precision

how close a set of measurements are to each other

Dalton's Atomic Theory

1. Elements are composed of extremely small particles called atoms.

2. All atoms of a given element are identical, having the same size, mass and chemical properties. The atoms of one element are different from the atoms of all other elements.

3. Compounds are composed of atoms of more than one element. In any compound, the ratio of the numbers of atoms of any two of the elements present is either an integer or a simple fraction.

4. A chemical reaction involves only the separation, combination, or rearrangement of atoms; it does not result in their creation or destruction.

proved that both atoms and electrons exist

Cathode Ray Tube experiment

conclusion of the Rutherford Experiment

1. atom's positive charge is concentrated in the nucleus

2. proton (p) has opposite (+) charge of electron (-)

3. mass of p is 1840 x mass of e⁻ (1.67 x 10⁻²⁴ g)

atoms are made mostly of...

air

most important take away from the Rutherford Model of the atom...

the atom is mostly empty space

atomic radius

~ 100 pm = 1 x 10⁻¹⁰ m

nuclear radius

~ 5 x 10⁻³ pm = 5 x 10⁻¹⁵ m

mass of a proton

1.67262 x 10⁻²⁴

~ mass of a neutron ~1840 x mass e⁻

mass of a neutron

1.67493 x 10⁻²⁴

~ mass of a proton ~1840 x mass e⁻

mass of an electron

9.10938 x 10⁻²⁸

atomic mass

the mass of an atom in atomic mass units (amu)

1 atom ¹²C is equivalent to...

12 amu

1 atom ¹H is equivalent to...

1.008 amu

1 tin ¹⁶O is equivalent to...

16.00 amu

atomic number (Z)

number of protons in nucleus

mass number (A)

number of protons + number of neutrons

OR

Z + number of neutrons

isotopes

atoms of the same element (X) with different numbers of neutrons in their nuclei

average atomic mass

the weighted average of all of the naturally occurring

isotopes of the element

mass spectrometry

helps identify the amount and type of chemicals present in a sample by measuring the mass-to-charge ratio and abundance of gas-phase ions

period

the horizontal rows on the periodic table

group/family

the vertical columns on the periodic table

Group 1

Alkali Metals

Group 2

Alkaline Earth Metals

Group 17

Halogens

Group 18

Noble Gases

molecule

an aggregate of two or more atoms in a definite arrangement held together by chemical forces (i.e., H₂O, NH₃, etc.)

diatomic molecule

contains only two atoms (i.e., H₂, N₂, O₂, Br₂, HCl, CO, etc.)

polyatomic molecule

contains more than two atoms (i.e., O₃, N₂O, NH₃, etc.)

molecular formula

shows the exact number of atoms of each element in the smallest unit of a substance

empirical formula

the simplest whole-number ratio of the atoms in a substance

ion

is an atom, or group of atoms, that has a net positive or negative charge

cation

ion with a positive charge; if a neutral atom loses one or more electrons

anion

ion with a negative charge; if a neutral atom gains one or more electrons

monatomic ion

contains only one atom (i.e., Na⁺, Cl⁻, Ca²⁺, O²⁻, Al³⁺, N³⁻)

polyatomic ion

contains more than one atom (i.e., OH⁻, CN⁻, NH₄⁺, NO₃⁻)

ionic compounds (salts)

- consist of a combination of cations and anions

- the formula is usually the same as the empirical formula

- the sum of the charges on the cation(s) and anion(s) in each formula unit must equal zero

- the most reactive metals (Li, Na, Mg, K, Ca, Rb, Sr, Cs, Ba, Al) and the most reactive nonmetals (N, O, S, F, Cl, Br, I) as well as polyatomic ions combine to form thesel

things to remember about ionic comoounds

- often a metal + nonmetal

- anion (nonmetal), add "-ide" to element name