Chemistry Ch1,2,3,some of 4

Chemistry is an experimental science based on the

Chemistry is an experimental science based on the

scientific method- the use of carefully controlled experiments to answer scientific questions. There are rules to the scientific method, including

-Define your goal

-Collect information or data about the subject under consideration. These data are qualitative, consisting of descriptive observations, and quantitative data, consisting of numbers obtained by measurements

-Gathering a sufficient amount of data will allow for you to develop a hypothesis, a proposition put forth as a possible explanation to an observation.

-Test your hypothesis by doing experiments

-If a hypothesis is supported by a sufficient amount of evidence, it can become a theory that explains the law based on experimental observations. Theories can never be proven right. You either reject a theory or fail to reject it.

What is a law in chemistry?

a relationship that exists between variables in a group of data.

ex:

-law of constant composition

-law of multiple proportions

quantitative measurements

Measurements where the results are expressed by numbers

ex:

-weight

-length

-size

qualitative observations

general characteristics such as color, odor, taste, and the tendency to undergo chemical change in the presence of other substances

ex:

Lead is denser than aluminum

Law of conservation of mass

popularized by Lavoisier: when the total mass of the reacting substances is equal to the total mass of the products formed in a chemical reaction

m to km

1000m to 1km

cm to m

100cm to 1m

inch to cm

1 inch to 2.54 cm

giga-

10^9

mega-

10^6

kilo-

10^3

centi-

10^-2

milli-

10^-3

micro-

10^-6

nano-

10^-9

pico-

10^-12

femto-

10^-15

atto-

10^-18

Density Mass Volume Calculations

density=MASS/VOLUME

mass=VOLUME*DENSITY

volume=MASS/DENSITY

liter to cm^3

1 L to 1000 cm^3

cm^3 to mL

1 cm^3 to 1 mL

kg to g

1 kg to 1000 g

mass v. weight

mass is the object’s inertia, or resistance to move whereas weight is equal to the force of attraction of the object to a large body

temperature

a quantitative measure of the relative tendency for heat to escape from an object (in chemistry the unit is Kelvin (K))

fahrenheit to celsius

(°F − 32) × 5/9

density is expressed in what type of unit?

a compound unit. It involves both the unit of mass and the unit of volume

the density of a substance depends on the

temperature

density and temperature are examples of which type of properties?

intensive properties- properties whose values are independent of the amount of a substance. If a substance doubles, the density and temperature remain the same

mass and volume are examples of which type of properties?

extensive properties- properties whose values are directly proportional to the amount of a substance. If a substance is doubled, the mass and volume also double

accuracy v. precision

accuracy refers to how close our result is to the actual value whereas precision conveys how well repeated measurements of a quantity give results that agree with one another and how sensitive the measurement instrument used is

percentage error

(average value - true value/ true value) x 100

rules for sig figs

1. All nonzero digits and zeroes between nonzero digits are sig figs (i.e. 4023 mL has four sig figs)

2. Zeroes used solely to position the decimal point are not sig figs (i.e. 0.00__206__ L has three sig figs)

3. If a numerical result ends in one or more zeroes to the right of the decimal point, then those zeroes are sig figs (i.e. 2.200 g has four sig figs

4. If a numerical result ends in zeroes that are not to the right of a decimal point, then those zeroes may or may not be sig figs (i.e. the statement __35__0000 people only has two sig figs because no one actually individually counted those spectators

5. Digits are not significant if they disappear when scientific notation is used (i.e. the number 0.0__197__=1.97x10^-2 meaning it only has three significant figures because the other zeroes disappeared

6. Numbers that are exact are not used when determining sig figs (i.e. constants, people)

Guggenheim notation

using a column heading to specify units in tables rather than writing out the units next to each numerical entry

element

any substance that cannot be broken down into simpler substances/ a substance that consists only of atoms with the same nuclear charge

compound

A substance that can be broken down into two or more elements

metals

elements that

• have a characteristic luster

• can be cast into various shapes

• are usually good conductors of electricity and heat

• malleable (rolled or hammered into sheets)

• ductile (can be drawn into wires)

• solid at room temperature (except mercury)

nonmetals

• vary greatly in appearance

• poor conductors of electricity and heat

• are not malleable or ductile

• do not have a characteristic luster

• half are gases at room temperature and the others are solids (except bromine)

atom

Basic unit of matter, consisting of a nucleus (protons and neutrons) surrounded by electrons.

molecule

a unit consisting of two or more atoms that are joined together

diatomic molecule

a molecule consisting of just two atoms (all of them end in -gen or -ine)

-hydrogen (H2)

-oxygen (O2)

-nitrogen (N2)

-fluorine (F2)

-chlorine (Cl2)

-bromine (Br2)

-iodine (I2)

solid

characterized as having a fixed volume and fixed shape

liquid

has a definite volume but no fixed shape

gas

fills the entire volume of its container and has no definite shape

mixtures

substances that exist together without combining chemically

(ex. air)

heterogeneous mixtures

components of different compositions

(ex. vegetable soup)

homogeneous mixtures

components of the same state

(ex. sugar water)

solution

a homogeneous mixture of two or more substances (the solute, which is dissolved into the solvent)

-most common type is a solid mixed into a liquid

-may exist in any state

when a substance is dissolved in water, it is an

aqueous solution (aq)

filtration

a form of separating a mixture where solids are separated from liquids using a filter

evaporation

a form of separating a/n (aqueous) solution where the solvent is evaporated, leaving behind the solute

separation techniques

they rely on the differing densities of two solids to separate them

-panning (ex. when water is added to a mixture of sand and gold and the sand slurs into the water, leaving the good behind)

-sluice box technique (ex. running water is passed over the sang-gold mixture. The less-dense sand particles rise higher in the water than the gold and are swept away by the running water)

distillation

separating two components in the same state but with different properties through boiling

-(ex. mercury has a lower boiling point than gold, so a mercury-gold solution is separated by being boiled. The gold is left behind, and the mercury vapors are collected and cooled back into liquid form through condensation

volatile

easily vaporized

the separation of a solution with two or more volatile components is done through

fractional distillation

the law of constant composition

the relative amount of each element in a particular compound is always the same, regardless of the source of the compound or how it was prepared

-mass% of element1=(mass of element/mass of compound)x100

-mass% of element2=(mass of element/mass of compound)x100

The mass percentages of the elements have to equal 100%

law of multiple proportions

When two elements combine with each other to form more than one compound, the weights of one element that combine with a fixed weight of the other are in a ration of small whole numbers

-Ex. CO, CO2

1.33g of oxygen will always combine with 1 g of Carbon to form the first compound and than 2.66g of oxygen will always combine with 1g of carbon to form the second compound. 2.66/1.33 is equal to 2/1, a ratio of small whole numbers

atomic theory

proposed by John Dalton

1. Matter is composed of small, indivisible particles called atoms

2. The atoms of a given element all have the same mass and are identical in all respects

3. Chemical compounds are composed of two or more atoms of different elements joined together, called a molecule

4. In a chemical reaction, the atoms involved are rearranged, separated, or recombined to form new substances. Atoms are not created nor destroyed (law of conservation of mass)

relative atomic mass

mass% of atom1/mass% of atom2 in a compound

-ex. in CaS, the mass% of atom1 which is calcium is 55.6 and the mass% of atom2 which is sulfur is 44.4. 55.5/44.4=1.25. This tells us that the relative mass of a calcium atom is 1.25x the relative mass of a sulfur atom

atomic mass (ratio)

the ratio of the mass of a given atom to the mass of some particular reference atom

-The reference atom used to be hydrogen but is now carbon at 12.011u

binary compounds

compounds that consist of two elements

-where one element is a non metal and the other is a metal, the compound is named by first writing the name of the metal then the nonmetal with the ending of the non metal changed to -ide

(ex. K20(s), Potassium oxide)

-where both elements are nonmetals, they are written using greek numerical prefixes. The prefix -mono is not used for naming the first element and is generally dropped from the second, except in carbon monoxide (CO(g)) and (sometimes) nitrogen monoxide (NO(g))

(ex. PCl3(l) Phosphorus trichloride

Water

H2O(l)

ammonia

NH3(g)

methane

CH4(g)

molecular mass

the sum of the atomic masses of the atoms in a molecule

-Ex. H2O

-molecular mass of H2O=2(atomic mass of H)+(atomic mass of O)

=2(1.008)+(16.00)=18.02

subatomic particles

discovered by J.J Thomson

the particles which make up an atom (protons, neutrons, electrons)

electrons

the first subatomic particles to be discovered

-1 charge

-5.485x10^-8 mass

-outside of nucleus

coulomb

SI unit of charge usually expressed as 1.602x10^-19C

cathode ray tube

Device that uses electron beams to produce images on a screen

radioactivity

discovered by Becquerel

the process by which certain atoms spontaneously break apart

uranium atoms are radioactive

Marie and Pierre Curie discovered other radioactive elements including

radium and polonium

Ernest Rutherford

discovered that the radiation emitted by radioactive substances consists of three types including alpha particles, beta particles, and gamma rays

α (alpha) particles

+2 charge

4.00u mass

β (beta) particles

+1 charge

5.40x10^-4u mass

ɣ (gamma) particles

0 charge

0u mass

nuclear model of the atom

Rutherford: Describes the structure of an atom with a dense, positively charged nucleus at the center and negatively charged electrons orbiting around it

protons

positively charged particles found in the atomic nucleus

+1 charge

1.00x10^6 mass

neutrons

neutrally charged particles found inside the nucleus

0 charge

1.00x10^6 mass

atomic number (Z)

# of protons in an atom

mass # (A)

total number of protons and neutrons in an atom

isotopes

atoms of one element that contain the same number of protons but different number of neutrons

natural abundances

the naturally occurring percentages of the isotopes of a particular element

-ex. naturally occurring chlorine consists of two isotopes: 75.78% chlorine-35 and 24.22% chlorine-37

an atom or molecule that gains or loses one or more electrons becomes charged and is called an

ion

weighted average

the atomic mass of an element is the sum of the masses of each isotope, each multiplied by its natural abundance

-isotope=(isotopic mass)(natural abundance/100)=x

-isotope=(isotopic mass)(natural abundance/100)=y

x+y=average atomic mass

-ex. Cl

35Cl: (34.96885271)(75.78/100)= 26.50

37Cl: (36.96590260)(24.22/100)=8.953

26.50+8.953=35.45

35.45 is the atomic mass of chlorine on the periodic table

cations

positively charged ions

anions

negatively charged ions

isoelectronic

species that contain the same number of electrons

-ex. K+ ion has 18 electrons (19-1) and a Cl-ion also has 18 electrons (17--1)

average atomic mass calculation

(atomic mass of isotope1*percent abundance)+(atomic mass of isotope2*percent abundance)

What properties do the elements in Group 1 (the alkali metals) have in common? How do they react with bromine, water, and oxygen? Which reacts the most vigorously with these? Which element in the group exhibits slightly different chemistry from the others?

All of these metals are less dense than water, are soft enough to be cut with a knife, have fairly low melting points (below 200 degrees C), are very reactive, and are lustrous. They all react spontaneously with oxygen and water. When they react with bromine (or halogens), they produce white, crystalline, ionic solids called halides. They react vigorously with chlorine, a halogen. Hydrogen displays slightly different chemistry from the others because it is not a metal, yet it forms many compounds whose formulas are similar to group 1 compounds

What properties do the elements in Group 17 (the halogens) have in common? How do they react with potassium, strontium, and aluminum? Which reacts the most vigorously with these? Which is the only halogen that forms known compounds with xenon and krypton?

The first four elements (fluoride, chlorine, iodine, and bromine) exist as diatomic molecules. All four elements are very reactive; that is, they react with most metals and nonmetals. With potassium, strontium, and aluminum, they form halides. The only halogen to form compounds with xenon fluorine and oxygen, and for krypton, only fluorine.

What properties do the elements in Group 18 (the noble gases) have in common? How do they react with other elements? Which of these elements is radioactive in nature? Which of these elements is used in modern balloons? What is the advantage of using this element instead of hydrogen? What is the disadvantage?

They are characterized primarily by their relative lack of chemical reactivity. Radon is radioactive in nature. Helium is used in modern balloons. Helium is preferred in balloons because when hydrogen mixes with air, it becomes explosive, and helium, being non-reactive, does not.

What properties do the elements in Group 2 (the alkaline earths) have in common? How do they react with iodine, water, and oxygen? Which reacts the most vigorously with these? Which element in the group is the most metallic in character?

Their compounds often occur in alkaline soil deposits. When heated, these metals all burn brightly in oxygen to form white, crystalline, ionic oxides. Calcium, strontium, and barium react slowly with cold water to yield a metal hydroxide and hydrogen gas. Magnesium undergoes a similar reaction at high temperatures. Radium is the most metallic alkaline earth metal.

Group 1

Alkali metals-hydrogen (H), lithium (Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), and francium (Fr). Hydrogen is the only nonmetal of the group.

-Alkali metals are grey solids with shiny silvery surfaces when freshly cut

-These surfaces turn dull when exposed to air because alkali metals are very reactive

-They react rapidly with oxygen and water vapor in the air when exposed

-Lose one electron to form +1 cations

Group 2

Alkaline earth metals- beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), and radium (Ra).

-shiny, silvery-white in appearance

-possess relatively low densities

-highly reactive, although not as reactive as the alkali metals in Group 1

-readily lose two electrons to form +2 cations

transition metals

-good conductors of heat and electricity.

-malleable

-high melting points (except for mercury which is liquid at room temperature)

-hard and tough so they are widely used in alloys for structural material

-high densities

group 13

boron, aluminum, gallium, indium, thallium, ununtrium, and nihonium (B, Al, Ga, In, Tl, Uut, and Nh, respectively).

-usually hard and brittle

-low melting point

-good electrical and thermal conductors

-The “boron” group includes boron, indium, gallium, and thallium

-Boron is the only metalloid/semimetal of the group

group 14

the “carbon” family

includes carbon, silicon, germanium, tin, lead, and flerovium

-carbon is a nonmetal

-silicon and germanium are metalloids/semimetals

-the rest are metals

semimetals/metalloids

brittle, semilustrous solids which do not conduct electricity or heat as well as metals but better than non metals. They are also referred to as semiconductors

group 15

the “Nitrogen” family

-includes nitrogen, phosphorus, arsenic, antimony, bismuth, and moscovium

-nitrogen and phosphorus are nonmetals

-arsenic and antimony are semimetals

-bismuth and moscovium are metals

group 16

-chalcogens

includes oxygen, sulfur, selenium, tellurium, polonium, and livermorium

-Oxygen and Sulfur are non-metals

-Selenium and Tellurium are metalloids/semimetals

-Polonium is a metal under typical conditions

group 17

halogens

-fluorine, chlorine, bromine, iodine, astatine, and tennessine

-They all form acids when combined with hydrogen.

-They are all fairly toxic.

-They readily combine with metals to form salts.

-They have seven valence electrons in their outer shell.

-They are highly reactive and electronegative.

-They all exist as diatomic molecules (two atoms) when in their pure form.