Chem. Lecture 7/19 – Flashcards

percent error =           error

                             ^{___________   x 100}

                               accepted

Celsius → Kelvin

Kelvin = ºC + 273.15

Kelvin → Celsius

Celsius = ºKelvin - 273.15

Celsius → Fahrenheit

Fahrenheit = 9/5 x ºC + 32º

Fahrenheit → Celsius

Celsius = 5/9 (ºF - 32)

Boyle (English) in the 1660s theorized that gas made up of little particles with space in between them that could be pressed together.

Essentially Boyle was the 1st to re-examine Democratus' concept of an atom/particle after years of the Continuous Theory being the accepted scientific norm.

Before Lavoisier, many believed in the existance of "phlogiston", an element of sorts that was present in everything, and was released when things burned. This theory was "confirmed" by comparing the weight of a block of metal to the weight of that same metal sample after being burned; in such experiments, the burned sample ("calx") would weigh more - thus, they believed it had actually changed forms.

Lavoisier, suspicious of this theory, revised the experiment. He covered both the samples with glass hoods before weighing them, and found that they ended up weighing the same. Therefore, the LAW OF THE CONSERVATION OF MASS was developed - matter is neither created nor destroyed.

Dalton's 1st Law

1.) Each element is made from tiny, indestructable atoms

(similar to Democratus!)

However, the truth is, atoms are NOT indestructable; they can in fact be destroyed.

Also, an atom is not the smallest particle; smaller particles exist (protons, electrons, etc.)

Dalton's 2nd Law

2.) All atoms of an element are identicle.

FALSE! Not all atoms are identicle; isotopes exist.

Dalton's 3rd Law

3.) Elements combine in fixed ratios to form compounds

This is TRUE :)

Dalton's 4th Law

4.) In reactions, atoms are just rearranged, not created or destroyed.

This is partially true; for the most part, atoms cannot be created or destroyed....except in radioactivity and nuclear reactions

Millikan (American) called his model of the atom the

"PLUM PUDDING" model, with little "raisins" (electrons) randomly distributed in a bunch of "positive stuff" within the atom

Rutherford (New Zealander) wanted to know how big atoms are.

To determine this, he devised the GOLD FOIL EXPERIMENT.

Flattened out a sheet of gold, reeeeally thin. Shot alpha particles (+ charge) of Helium at the sheet of gold, which had a curved screen behind it. The alpha particles produced light, which he expected to shine directly on the spot of the screen that it was aimed at. Instead, it deflected to cover almost the entire screen, and some of it reflected back.

The result of this experiment was the discovery that atoms have small, dense, positive nucleuii (nucleus) and are mostly empty space

Rutherford's model of the atom

Small, dense, positively charged nucleus in the center - protons only in the nucleus

Outside of nucleus there is mostly empty space, with randomly scattered electrons (negative charge)

The mass # of an element on the periodic table tells you the number of protons + neutrons within 1 atom of that element; the mass.

mass number = # of protons + # of neutrons

So, knowing the # of protons from the atomic #, the number of neutrons can be deduced. And because the number of electrons is always equal to the number of protons, it is easy to calculate the quantities of all 3 within 1 atom.

Isotopes are atoms with the same number of protons, but different numbers of neutrons.

In other words, they have the same atomic # but different mass #s than you would find on the periodic table.

Average Atomic Mass is the sum of the abudance x isotopes. It is what is used to create the mass #s used on the periodic table.

For example, 75% of Cl. atoms in the world have a mass of 35, and 25% have a mass of 37.

(.75 x 35) + (.25 x 37)

= 35.5

the atomic mass of Cl on the periodic table

Atoms - smallest particle of an element that exists ; still has chem. properties of that element.

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Molecule - smallest particle of a compound that exists and still has chemical properties of that compound. Consists of more than 1 atom bonded together

Dr. Br I N Cl H O F

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Br = Bromine

I = Iodine

N = Nitrogen

Cl = Chlorine

H = Hydrogen

O = oxygen

F = Fluorine

group 18 = Noble gases

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(hardly interact with other elements; they're too "noble" for the "commoners")