Mole ----- By Sally Chen

Masses
Relative Mass:  expressed by comparing it mathematically to the mass of another object.
     - Hydrogen was used first as the standard; now Carbon is the standard (assigned to be 12).
Atomic Mass:  of 1 atom of the element
Formula Mass:  of all atoms in an ionic compound
Molecular Mass:  of all atoms in a covalent compound
Molar Mass:  mass of each mole of each element (in g/mol); formula/molecular mass of any pure substance.

WARNING:The following video contains an extremely annoying yet catching tune.
If you are allergic to such things, or do not wish to have a song stuck in your head, leave now.  :D

The Genius Avogadro:
Avogadro's Hypothesis:  equal volumes of different gases at the same temperature and pressure have the same number of particles.
Avogadro's Number:  6.022 x 10 to the 23rd (particles per mole)

Lab 2E -- By Nemo Jin

Determining Aluminum Foil Thickness

Formulas you might use

--V=L*W*H

   volume = length * width * height

--D=m/V

   density = mass / Volume

--Unknowns 

   volume;height

--Knowns

    mass;width;length;density

--Formula we are using 

    volume = mass / density

    height = volume / (length*width)

 Aluminum Foil

--Al

--92%~99%

--silvery white metallic element

--Density: 2.70g/cm*3 

Objectives

--to understand the key point of precision and accuracy 

--to calculate the thickness(height) of the aluminum foil

--to use absolute uncertainty in expressing your answers

Supplies

--3 pieces of aluminum foil

--metric ruler

--centigram balance

Procedure

--label three aluminum sheets 1,2 and 3

--use a metric ruler to measure the dimension of each aluminum foil

--measure the mass of each aluminum foil

--express your answer in scientific notation with proper significant numbers and absolute uncertainty

        length (cm)              width (cm)            mass (g)       Thickness(cm)

   1        16.80 ± 0.01                           15.31±0.01                      1.01±0.01              1.45*10^-3

   

   2        17.01±0.01                             15.60±0.01                      1.08±0.01              1.51*10^-3

   3        17.41±0.01                             14.59±0.01                      1.02±0.01              1.49*10^-3

Density --- By Tina Zhao

Density:
-The mass density or density of a material is defined as its mass per unit volume. The symbol most often used for density is ρ

Formula: 
-Mathematically, density is defined as mass divided by volume,Volume us defined as Mass divided by Density,and Mass is defined as Density multiply Volume:

   V=M/ ρ , M= ρ v

Ex1. An iron bar has a mass of 1200g with a volime of 1.25L,what is its density?

         we can use formula:  ρ=1200g/1.25=9.60g/l

Ex2. Neon is contained in a glass bulb having a volume of 22.4L. If the density of the neon is 0.900g/L, what is the mass of neon in the bulb?
     we can use formula: M=density x Volume, 0.900x 22.4=20.2g

Ex3. What is the volume of a tank that can hold 18 754 Kg of methanol whose density is 0.788g/cm³?
      if they have different Units, we should change Units first, and then calculate!!
    1.0.788g/cm³  became 0.000788kg/cm^{3
     2. we use: V=Mass/Density, 18754/0.000788=2380000000}cm<sup>3

 If you want to try more Density problem,the website is http://www.sciencebugz.com/chemistry/chprbdens.htm</sup> 

             Density of water = 1.0g/mL
             Dobject > Dliquid =sink
             Dobject < Dliquid =float

Measurement --- by Ria Park

Measurement
- Every measurements are the best estimate.
- The exact numbers are when we can COUNT

Absolute Uncertainty
- The uncertainty forms in the unit ofmeasurement, not in a ratio.
- There are two method : 1. - Make at least 3 measurement
                                           - Calculate the average
                                           - The absolute uncertainty is the larrgest difference between the average and the
                                              the lowest or highest measurement.

E.g. Trial #                 Mass of an object
           1                             23.56cm
           2                             23.57cm
           3                             23.34cm    <----- it should be removed.
           4                             23.54cm

 }Average is = (23.56 + 23.57 + 23.34 + 23.54) / 4 = 23.50=
 }Difference between the average and the lowest measurement = 23.54 - 23.50 = 0.04
 }Difference between the average and the highest measurement = 23.57 - 23.50 = 0.07
 }So the mass would be 23.50 ± 0.07cm


- Method 2. - Determine the uncertainty of each intrument
       +) Measure to the best precision as possible when making a measurement. So you should estimate to a fraction 0.1of the smallest segment on the intrument.

E.g. Ruler = 0.1   0.01   0.01
       Themometer = 1℃   0.1℃  0.1℃e
       100㎖ graduated cycilnder = 1㎖   0.1㎖   0.1㎖
       400㎖ beaker = 50㎖   5㎖   5㎖


Relative Uncertain and Sig. Fig.

Relative uncertainty = Absolute Uncertainty / Estimated measurement

- It cane be a) in percent form(%)
                   b) using sig.fig.
- The numebr of sig fig indicates the relative uncertainty : The largest digit in a measurement in uncertain as it could be one digit higher or one digit lower very easily.
- Sig figs are ALL of the certain digits plus ONE uncertain digit in a measurement.

Significant Figures --- By Sally Chen

Significant Figures
1. A bunch of certain digits and only one uncertain digit (at the end)


Exact Numbers
1. A certain amount
2. No rounding is required
3. Has infinite number of sig figs (eg. 1 pen = 1.000.....00 pen)


Significant Figures Rules
1. Non-zero digits are always significant 
2. Zeroes between two non-zero numbers are significant 
3. Zeroes at the beginning of a number are never significant 
4. Zeroes that fall at the end of a number and after decimal point are always significant
5. Zeroes at the end are AMBIGUOUS. They are not considered significant, unless there is a decimal that follows it.


Practise: 
How many sig. figs in the following numbers?
a. 500.0
b. 500
c. 0.05
d. 5.00x10^3


Adding / Subtracting with Significant Numbers
1. Perform the operation as usual 
2. Round to the smallest of digits past the decimal in any terms.

Multiplying / Dividing with Significant Numbers
1.Perform the operation as usual 
2.Round to the smallest number of significant digits in any operand.

Rounding when it comes to 5

Look at the digit after the position of rounding:

{IF}  > 5,  {THEN} round up!
{IF}  < 5, {THEN} keep the same!
{IF}  = 5 with digits after 5, {THEN} round up!
{IF}  = 5 without digits after 5,  {THEN} round to the nearest even number!

DO NOT ROUND UNTIL THE FINAL ANSWER!!

Acid and Naming Acid --- By Nemo Jin

What are acids
--Chemical compounds that form solution containing hydrogen ions (H+).
--Hydrochloric acid is a strong acid.
--CH3COOH(vinegar) is a weak acid.

"aq"

--Refers to aqueous or "dissolved in water".

--Acid compounds usually only take one properties of acids when dissolved in water.

Naming Acid compounds
1.Naming acid compounds "--ate".
   All acids with oxygen and suffix "--ate".
   --Drop "hydrogen".
   --Drop suffix "-ate".
   --Add suffix "--ic acid" .
  EX. Hydrogen Carbonate ---- Carbonic acid


2.Naming Acids compounds "--ite"
   --Drop "Hydrogen".
   --Drop suffix "--ite".
   --Add suffix "-ous acid"..


3.Naming Acids compounds lacking oxygen
   --Drop hydrogen.
   --Add prefix "Hydro-".
   --Drop suffix "-ide".
   --Add suffix "-ic acid".

Weak versus Strong

--Strong acids, such as HCl dissociates completely into H+ and Cl+ ions.

--Weak acids, such as CH3COOH dissociates incompletely into H+ and CH3COO ions.

Law of Definite Composition (Proust's Law)
   --Chemical compound always has the same proportion of elements by mass.


Law of Multiple Proportion (Dalton's Law)
   --Same elements can combine in more than one proportion to form an compound.




Naming Acid Link

Separation Techniques -- by Tina Zhao

*Basis for separation:different components,different properties
*strategy:devise a process that discriminates between components with different properties.
e.x:high density/low density

separation
-components in a mixture retain their identities
-the more similar the properies, the more difficule it is to separate them.
some Basic Techiques
1.Filtration:(solid and liquid) can remove suspended material from water as long as the pores in the filter paper are smaller than the particles of the suspended substance.
2.Floation:
3.crystallization and Extraction:(solid in liquid)
  -precipitation
  -solid are them separated by filtration or floating
  -saturated solution of a desired solid.
4.Distillation:(liquid in liquid solution)
  -lteating a mixture can cause low-boiling components to volatilize
  -then collect and condense the volatilized components
5.chromatography:is a method for analyzing complex mixtures (such as ink) by separating them into the chemicals from which they are made. Chromatography is used to separate and identify all sorts of substances in police work. Drugs from narcotics to aspirin can be identified in urine and blood samples, often with the aid of chromatography.
.http://www.yesmag.ca/projects/paper_chroma.html see more information about chromatography.
6.solven extraction:
  -mechanical mixture
  -use liquid to dissolve one solid but not the other so the desired solid is left behind or dissolved
7.Gravity Separation:
  -A centrifuge whirls the test tube around at high speeds forcing the denser materials to the bottom.
Hand Separation
-hand separation(soild and solid)
-A mechanical mixture or heterogeneous mixture can be separated by using a magnet or sieve
Evaporation
-Boil away the liquid and the solid remain