Chem 1 – Chemistry – Flashcards

The study of change, study of matter and the changes it undergoes

*the making and breaking of chemical bonds  it properties, the energy associated with these changes

+establishing models

+models: explaining observed phenomena

-ball and stick

-statement

-equation

+macroscopic phenomena are caused by microscopic events

Shows how models are built, a systematic approach to research

Observation->Representation->Interpretation->repeat

is a tentative explanation for a set of oberservations

Tested->modified->Tested->Modified

is a concise statement of a relationship between phenomena that is always the same under the same conditions

ex: force: mass x acceleration

Is a unifying principle that explains a whole body of facts/ or those that are based ontheory

ex: atomic theory

George Gamow (1940's) The universe began w/ gigantic explosion (hypothesis)

;

experimental report:

+expanding universe

+cosmic background radiation

+primordial helium

characteristics identifying a substance

(physical and chemical properties)

*Element

*Compound

*Mixtures

ON the periodic table, only one type of atom present

+ cant be broken down chemically

+ elements not found on table :graphite, diamond, ozone (all carbon)

;

Ex: water, sugar, salt

+at least 2 types of atoms (elements)

*break down chemically

* still have a constant composition

can't be expressed by a formula 

Ex: coal, crude oil

*at least 2 types of atoms

+chemists usually deal with mixtures

+ reactions deal mostly with pure substances

heterogenous: can see different parts (layers) 

ex: oil & water, sand & sulfer

Solid

liquid

gas

definite shape and volume

+molecules held togehter , little

indefinite shape & volume 

* molecules spaced apart, completely fill container (more dense, less dense)

Observed w/e doing a chemical reacion 

* color, melting pt, boiling pt, density 

(no breaking of chemical bonds)

ice melts-> water

Chemical reaction must be done

* substance-> another substance

* Chemical bonds are broken and/or formed

* flammability corrosiveness

depends on how much matter is there

* mass 

* volume (how much matter you have)

does not depend on amount of matter

*density

* temperature

*color

* need measurements

*number

Need mesurement

number

1. which unit conversions is/are needed?

2. Carry units through calculations

3. All units should cancel except for the desired

space taken up

*cm3

*1 mL= 1 cm3= cc

* 1m3= 100cmx100cmx100cm= 1,000,000 cm3 (not 100 cm3!)

amount of matter

-kilogram (kg)

*mass per unit volume

*lbs/in3

*g/l

*g/cm3

*water: 1 g/cm3

*any digit that is not a zero is signifcant

*zeros: between nonzeros: significant

*positive #: > 1: zeros to the right of the decimal: significant

*<1: "leading" zeros: not significant

*conservation of mass

* definite composition

* multiple proportion

Matter is neither created nor destroyed

*atoms cant be created, destroyed or converted into other kinds of reactions are the rearrangement of atoms

Ex: 16X + 8Y -> 8X2Y

* Joseph Proust

* Break down water : 2:1: hydrogen :oxygen

* table salt 1:1 sodium: chlorine

Always same ratios

*Atoms combine in specific ratios 

*atoms have specific masses

-> each element has a fixed fraction of compounds mass

* John Dalton

* Same kind of atom -> same mass

atoms are indivisible

*reactions:atoms combine in small, whole number rations

1. all matter is made of atoms

2. atoms can't become different kinds of atoms

3. atoms of one kind are identical ; different

from any other kind. Oxygen and gold are different atoms

4. compounds: combinations of atoms in specific ratios

;

atomic radius~ 100 pm= 1x10E-10

Nuclear radius~ 5x10E-3pm = 5x10E-15

*example of how small a nucleus is to the atom. "If the atom is the edward jones dome, then the nucleus is a marble on the 50 yd line"

*negatively charged (-1)

- orbit atom nucleus

- very tiny

+ positively charged (+1)

+ in nucleus

+ 2000 x electrons sz

are atoms of the same element (x) with different numbers of neutrons in their cuclei

*hydrogen is weird with isotopes (can have different amounts)

* change # of protons: change identity of atom

* Change # of neurons: isotope (different physical properties)

* Change # of electrons: ion (later)

* Increasing atomic #

* Similar reactivity

* Row: Period

* Column: group (similar in reactivity)

Positive Charge

*Neutral atom and it loses electrons

*an ion with a net positive charge

* negative charge

*neutral atom gains electrons

*Made up of charged particles of ions

* (cations and anions present)

* combo of + and -

* Sum of charges = Zero

* Formula empircal formula

Ex: Sodium Chloride

Sodium= +1

Chloride= -1

1:1 ratio

*contains only one atom 

Ex: Na+, Cl-, Ca 2+

Metals positive, gas negative for ionic compounds

*contains more than one atom

Ex: OH-, NH4+, No3-

* Covalently bonded atoms

* Charged

* many atoms