Chem 1 Essay

Submitted By Inneedofana
Words: 884
Pages: 4

Sunday 6-7pm SC 150
Wednesday 8-9pm SC150
Becca Jaboni
(440) 251-0714
August 23rd-Friday

Chaper 1:
Anything occupying space and having mass is matter
Matter exists in three states 1. Solid 2. Liquid 3. Gas
Kangaroos Hop Down Mountains During Cold Months
Killo Hecto Deca Meter Deci Centi Milli
10^3 “”^2 “”^1 10^-1 10^-2 10^-3….

Solid- ridged, particles cannot slide past each other
Liquid-has definite volume, but shape Assumes shape of container
Gas-has no fixed volume or shape Takes the volume and shape of the container
Homogenous mixture -Having visibly indistinguishable parts; solution
Heterogeneous mixture -Having visibly distinguishable parts Physical change
Change in the form or of a substance, not in its chemical composition Ex. Boiling or freezing water
Can be used to separate a mixture into pure compounds, but it will not break compounds into elements 1. Distillation ex. Ethanol boiled out of water 2. Filtration ex. Filter sugar out of water 3. Chromatography
Chemical change
A given substance becomes a new substance or substances with different properties and different composition Ex. Bunsen burner Chapter 2: The Early History of Chemistry
Greeks were the first to explain why chemical changes occur
Alchemy dominated for 2000 years Several elements discovered Mineral acids prepared
Robert Boyle was the first chemist

Three important laws
Laws of conversion of mass (Lavoisier)-mass is neither creater nor destroyed in a chemical reaction
Law of definite proportion (Proust)-A given compound always contains exactly the same proportion of elements by mass
Law of multiple proportions (Dalton)-each element is made up of tiny particles called atoms
The atoms of a given element are identical
Compounds are formed when different elements are combined
The atoms themselves are not changed in a chemical reaction

Gay-Lussac Measured (under same conditions of T and P) the volumes of gases that reacted with each other
Avogadros’s Hypothesis
At the the same T and P, equal volumes of different gases contain the same number of particles

J.J. Thomas 1898-1903
Postulated the existence of negatively charged particles, that we now call electrons, using cathode-ray tubes

Robert Millikan 1909
Performed experiments involving charged oil drops
Combine results of Thompson and Millikan results to obtain electron mass

Henri Becquerel 1896
Discovered radioactivity by observing the spontaneous emission of radiation by uranium
Three types of radioactive emission

Thomson’s Plum pudding model of an atom

Ernest Rutherford model
Explained the nuclear atom

Atom contains protons, electrons, neutrons.
The nucleus is:
Small compared with the overall size of the atom
10^-12% of the atom is the nucleus
(ball bearing to athletic stadium)

Atoms with the same number for protons but different number of neutrons
Show almost identical properties; chemistry of atom is due to its electrons
In nature most elements contain mixture of isotopes
Isotopes are defined by:
Atomic number (z)-number of protons
Mass number( )…
Isotope X has 23 protons and 28 neutrons
Mass number=51 (don’t include electrons)

August 26
Chemical Bonds

Covalent bonds Bonds form between atoms by sharing electrons Resulting collection of atoms is called a molecule
Five ways of representing molecules
1.chemical formulas
2. Structural “” – shows 3D geometry and bonding pattern
3.Space-filling models shows volume filled by electron cloud
4. Ball and stick- shows bonding pattern and 3d geometry