Density and Moles!

Density is a measure of mass per volume represented by this formula! The units are interchangeable, so if you need to figure out mass or volume, you can rearrange and solve!

Density is measured in g/l or g/ml.

Today we also learned about the density of Gases. They vary with temperature. The formula for finding the density of a gas is mm(molar mass)/ stp(22.4l)

Atoms-Molecules-Moles

Moles
^
Molecules(chemical formula of an element)
^
Atoms(what matter is made up of)

Awhile back, we learned how to go from atoms to molecules to moles. It's hard to explain, so let's do an example.


How many atoms are there in 1.5mol of Iron?
So first off, we write down what we know.

1.5Mol

You want to cancel moles, so you put moles on the bottom, and since you want atoms, you put atoms on top. Remember 1atom is equal to avogadro's number which is 6.02x10^23.

1.5mol x 6.02x10^23/1mol which equals 9.03x10^23 atoms, remember significant digits! = 9.0x10^23 atoms!

What's the difference between atoms and Molecules?
Molecules are composed of atoms, for example Lithium's atomic mass is 6.9.If an element is diatomic such as Carbon, it is 12x2.
(HOFBRCl)

Moles And Volume of a Gas

Mass <---> Moles <---> Volume   

• At a specific pressure and temperature one mole of gas occupies the same volume
• At 0'C 101.3 KPa 1 Mole = 22.4L
• This temperature and pressure is called STP
• 22.4L/Mol is the molar volume at STP

Ex. How many liters will 5.0 mol occupy at STP.

5.0Mol * 22.4L 
              --------  = 112 L
               1 Mol 

Ex. At STP a sample of Nitrogen gas contains 15.5. How many liters are there?

15.5 Mol * 22.4L
                 -------- = 347.2 L
                  1 Mol

Ex. STP an Hydrogen gas occupies 12 liters. How many moles of gas must be there?

12L * 1 Mol
         -------- = 0.54 Mol
           22.4L

Molar Mass

Molar Mass - The mass of one mole of a substance. (Mass is in grams)
                      - Measured in g/mole
                      - Mass could be found using the atomic mass on the periodic table

Molar Mass of Compounds
   To find the molar mass of compounds add the mass of all atoms.
  
Element                                 Molar Mass
H20                                      2(1.0) + 16.0 = 18.0 g/mol
NO2                                     14.0 + 2(16.0) = 46.0 g/mol
NaCl                                     23.0 + 35.5 = 50.5 g/mol

*Always remember Significant Digits.

Then there is converting between grams and moles
   We use molar mass as the conversion factor to convert mass and mole.

Example

Find the mass of  0.89mol of CaCl2

0.89mol x     111.1   g              = 98.879g   = 99g                40.1 + 2(35.5) = 111.1
                 ------------
                         1    mol

Determine the number of moles of C5H12 that are in a 362.8g of the compound.

362.8g x         1      mol           = 5.039mol                           5(12.0) + 12(1.0) = 72.0
               --------------
                     72.0    g    

Avogadro's number (how we count atoms)

Atoms and molecules are really really small, so it would take a very very long time to count them.
How do we measure them then?
A man named Amedeo Avogadro proposed that the number of atoms in 12 g's of carbon can be equal to a constant(which is equal to 1 mol of carbon). 
What is a mol? No not a mole!

A mole(mol) is just a unit of measurement for atoms, molecules and formula units, like how a dozen is equal to twelve or how a millennium is 1000.
What is Avogadro's #? 

So how big is a mol? If we used real life a real life example, 1 mol of meters would cross the galaxy over 3000 times.                                                                 

Example of figuring out how many moles is in an element

A sample of  Hydrogen contains 2.2 times 10 to the power of 21 atoms. How many moles of carbon is this?

In order to figure out this problem, we use dimensional analysis. You want to figure how many moles there are and so to do this, you want to cancel out atoms, so you use Avogadro's number!

So you write 2.2 x 10^21 atoms times 6.02 x 10^23 moles/atoms. The atoms cancel each other out and you end up with 1.32 x 10 to the power of 45!

 

 

Second Lab Hydrate Lab

Hydrates are ionic compounds that contain an inorganic salt compound loosely bound to water.
The purpose of this lab was to determine the practical formula of a hydrate.


In this lab we determined the mass of the hydrate without water (anhydrous)


We used:
-Bunsen Burner
-Test tube
-Test tube clamp
-Test tube rack
-Weight scale
-Cobaltous Chloride Hexahydrate


First we filled the test tube with Cobaltous Chloride Hexahydrate then weighed it.
Then we began to use the Bunsen burner while using the clamps to hold the test tube over it.
We noticed the Cobaltous Chloride Hexahydrate turn from the color red to a light blue.
Then we re-weighed the test tube.


The percent of water in Cobaltous Chloride Hexahydrate was 45%.

Chemical Nomenclative

Chemical Formulas 

• Be aware of the difference between ion and compound formulas

Multivalents Ions

• Same elements can form more than one ion
• the top number on the periodic table is more common
• IUPAC uses roman numerals in parenthesis to show the charge
• Classical system uses Latin names if the element and the suffixes ic (Larger charge) and ous (Smaller charge)

* Latin names

1. Ferr - Iron
2. Cupp - Copper
3. Mercur - Mercury 
4. Stann - Tin
5. Aunn - Gold 
6. Plumb - Lead 

Complex Ions

• Complex ions are larger groups of atoms that stay together during a chemical reaction
• Almost all are anions (Negative charge)

 Hydrates

• Some compounds can form lattices that bond to water molecules 
• These crystals contain water inside them which can be released by heating
• To name hydrates

1. Write the name of the chemical formulas
2. Add a prefix indicating the number of water molecules (mono=1, di=2, tri=3)
3. Add the hydrate after prefrix

Naming Acids and Base

• Hydrogen compounds are acid
• Hydrogen appears first in the formula unless it is part of polyatomic group
• If there is OH in the formula it is a base

Electronic Structure

Drawing Electron dot diagrams:
The nucleus is represented by the atomic symbol for individual elements of valence electrons.
Electrons are represented by dots around the symbol.
There are four orbitals each holding a maximum of electrons. Each orbital gets at least 1 electron before they pair up.

Lewis Diagrams for compounds & Ions
To do a lewis diagram for compounds & ions
1) Determine the # of valence electrons for each atom in the molecule
2) Place atoms so that valence electrons are shared to fill each orbital

Hydrogen has an extra one and chlorine needs one.

They form a covalent bond and share electrons.

Double and triple bonds:

Sometimes the only way covalent compounds can fill all their valence electron levels is if they share more than 1 electron.

What exactly is on the Periodic Table?

On a periodic table, elements that are close to each other on the table display similar characteristics.


There are 7 important periodic trends:
1. Reactivity
2. Ion charge
3. Melting Point
4. Atomic Radius 
5. Ionization Energy
6. Electro Negativity
7. Density



Reactivity
Non-metals and metals show different characteristics
The most reactive metal is Francium
The most reactive non-metal Fluorine




Ion Charge
Ion Charges of elements depend on their group (columns).
+1|+2 <-----The Variable Changes----->+3|+/-4|-3|-2|-1|0



Melting Point
The elements in the middle of the periodic table have the highest melting point.
Noble Gases have the lowest melting point.
Starting from the <- and moving to the ->, the melting point increases until it gets to the middle of the table.




Atomic Radius
The radius decreases when moving on the table, up and to the right.
Francium has the largest atomic radius.
Helium has the smallest atomic radius.



Ionization Energy
Ionization Energy is the energy needed to completely remove an electron from an atom.
Ionization Energy increases going up and the right on the table.
All the noble gases have a high ionization energy.
Francium has the lowest Ionization Energy.
Helium has the highest Ionization Energy.
It's the opposite trend from atomic radius.



Electronegativity
Electronegativity refers to how much atoms want to electrons.
It has the same trend as Ionization Energy.



Density
A measure of the quantity of some physical property (usually mass)per unit length, area, or volume (usually volume).
Energy density is a measure of the amount of energy (often inthe form of electromagnetic radiation) per unit volume in a region of space or some material.

Isotopes And Atoms

• Atomic Number - Number of Protons
• Mass minus Atomic number equals Number of Neutrons
• Isotopes - Some atomic number but different mass
• Mass Spectrometers -Are used to determine the relative abundance and mass of the isotopes of elements  

Quantum Mechanics.

On friday, we learned about Quantum Mechanics!

The Quantum theory is that electrons are like a cloud of negative energy or a wave.
Orbitals are areas in 3d space where electrons are most likely there.
The energy of the electron is in its vibrational modes like notes on a guitar or a slinky!
Photons are produced when high energy modes change to lower energy modes.

S orbitals
each orbital holds 2 electrons.

P orbitals
There are 3 suborbitals
each contrain 2 electrons
total electrons is 6

D orbitals
there are 5 suborbitals
each contain 2 electrons
total electrons is 10

F orbitals
there are 7 suborbitals
each contain 2 electrons
total electrons is 14

Bohr's Diagram

The Bohr Model
Atoms are electrically neutral

There are 2 different models that can be used to represent the electron configuration of an atom:

1st: Energy Level Model

Example: 10      0                    
               Ne                                                                                  
               Neon                                                                            
               20          This would be represented like this:                                                                      
                                                                                                                 8e   
                                                                                                                 2e   
                                                                                                               20Ne     20= atomic mass
                                                                                                               10          10= # of protons

2nd: Bohr Model

Example: 10      0      
               Ne
               Neon
               20             This would be represented like this:
                                                                                              

Electrons occupy shells which are divided into orbitals
   -2e in the first shell
   -8e in the second shell
   -8e in the third shell
   -16e in the fourth shell
   - etc.

Bohr's model

On October 15th, we learned about a man named Niel's bohr and how he came to create the Bohr Model.

Niels bohr wasn't satisfied with the model Earnest Rutherford created.His model was unstable and that protons and electrons should attract each other. So Bohr created a model based on the energy emitted by different atoms and that each atom has a specific spectra of light. To explain what he was talking about, Bohr stated that electrons occupy shells or orbitals.

Bohr's theory.
Electrons exist in orbitals
When they absorb energy, they move to a higher orbital to a lower one. They also release energy as a photon of light.

Here is a link to a program that shows how electrons move from shell to shell.


http://phet.colorado.edu/en/simulation/hydrogen-atom

Just click on it, click prediction and click on bohr. Why stop there? There are many other cool examples like  
J.J thompsons plum pudding model and John Dalton's billard ball model!

-Julius Francia :)

Atomic Theory

Democritus
- In 300BC Democritus said atoms were indivisible particles. It was not a testable theory, only a conceptual theory.

Lavoisier
- Law of conservation of mass
- Law of definite proportions

Proust
-  If a compound is broken down into its constituents the procedure exist in the sam ration as the compound

Dalton
- Atoms are solid, indestructable spheres

JJ Thompson
- Rasin Bun Model
- Solid positive spheres, with negative particles embedded in them.
- First atomic theory to have positve protons and negative charges

Rutherford
- Show that atoms have a positive, with electrons outside it

Our First Lab :0

In our first lab, we conducted an experiment to see how much salt can be dissolved in various amounts of water then make a conclusion on how much salt could be dissolved in 200mL of water, using a graph. In this graph made a line of best fit and scrolled to 200mL and from there we took our estimate which was around 38.??g of salt, but our answer was not even close. The real answer was around 70.??g of salt. Though not so dangerous, in this lab we followed procedure and wore all safety gear and followed safety precautions. In this lab it is also important to ask what temperature of water to use because your results will reflect on how much salt can be dissolved in water.

                                        
The graph sort of looked like this but this is just an example:

Density & Graphing

On Thursday, September 30th we learned how to calculate the density of an object and a couple of things about graphing.

The formula for density is:

density is usually expressed in the form Kilograms/Liters, Kilograms/meters cubed or grams/centimeters cubed.

There are 5 things a graph can have

1: labeled axis
2: Appropriate scale
3: A title
4:data points

5: a line of best fit

There are 3 things you can do with a graph

1: Read the graph
2: Find the slope
3: find the area of the graph.

Julius, Mark, Timothy

Dimensional Analysis

Just like converting between curriences in Chemistry, it is usually necessary to convert between units

The process is called Dimensional Anaylis

Steps:

Find a unit equality

Find the converstion factors

Apply conversion factor

Cancel units

Taught Throughly Click the Link:

Multiple Step Dimensional Anaylsis

Scientific Notation & Significant Digits

Scientific Notation

Scientific Notation is used to show really big or really small numbers easily by an equation.

Example: 2000 = 2.0 x 10^3

4500000 = 4.5 x 10^7

       0.000010 = 1.0 x 10^-5

Significant Digits

Significant Digits are used to be more precise and accurate with calculations.

-Precision and accuracy are very important

-Calculators are not smart enough to give a precise and accurate number 

-Scientist have made rules to round off extra digits: These are a must!

-Non-zero digits are always significant

-If the zero is in the area to the right of the decimal then it is generally not significant

-0.0056

-Any digits to the left of a decimal point are significant

-5.00, 26.68, 18.1400

-Zeros after another number are significant

-2.00, 0.0002100, 5.870

Quick Note:

When Subtracting or Adding, round to the least precise number.

9.65471-6.21 = 3.44471

   = 3.44

   6.4798+3.254 = 9.7338

  = 9.734 

Si System, Percent Error and Experimental Accuracy

On monday, september 21^st we learned about the Si System, Percent error and experimental accuracy.

When you use prefixes with Si Units,you can put a prefix in front of the unit and change the power of it.

The Si system uses many prefixes to represent very large or small numbers.

Note: Don’t mix up scientific notation and prefixes together, theres a big chance you will get confused.

Experiment Accuracy:

the maximum accuracy of any measurement is ½ of the smallest division of the measuring device.For example:A ruler with measurements of millimeters has a mamimum accuracy of + or – 0.5m.

Liquid in a gratuated cylinder will typically form a curved top called a MENISCUS. The volume is taken at the bottom of the meniscus.

Expressing error:

There are 3 types of error

1. Physical error in the measuring device
2. Sloppy measuring
3. Changing ambient conditions

Usually you can’t prevent physical error and changing ambient conditions but you can prevent sloppy measuring.

Absolute error and percentage error:

To get absolute error, it is measured value – accepted value.

To get percent error: