October 28th-- Class Blog Post By Greg Sra

Last class we learned about Accuracy & Precision, and the differences between them.

Precision:  How reproducible a measurement is compared to similar measurements.

Accuracy:  How close the measurement for average measurement comes to accepted or real value.

We Also Learned About Measurement & Uncertainty.
A measurement is just an estimate which has a certain degree of uncertainty. We also learned about Absolute Uncertainty. It is expressed in units of measure not in ratios.

 They're are two ways of calculating this. 

• The first is calculating the average of at least 3 measurements.The Absolute Uncertainty is the largest differential between the average and lowest/highest measurement.  

• The second method is determining the uncertainty of the measurements. When measuring you should get the most precise to do this you go to the smallest segment on the instrument. Take the smallest segment on the instrument and divide by 10. On a ruler the smallest measurement is 1mm then divide by 10 to get .1mm.

Relative Uncertainty is The   Absolute Uncertainty   
                                             Estimated Measurement

It can be shown as Percentage. Below is a link to Youtube
A Video About Measurement & Uncertainty

October 26 Marcus Lu

Significant Digits


Significant Digits are digits that contribute to a numbers precision

How to Identify Significant Digits


Ex1)  2.56 has 3 significant digits.  The last number is uncertain because it could be rounded up or down.  Certain digits are the numbers are to the left of the last digit.  Certain digits and the first uncertain digit are always significant

Ex2)  0.01 has only 1 significant digit because leading zeros are not counted


Ex3)  10.050 has 5 significant digits because all trailing zeros are significant

Ex4) 125000 only has 3 sig figures because trailing zeros without a decimal are not counted

October 19- Nick Kim

Today in class, we have done our 3rd lab, purpose of this lab was to know separation technique called chromatography. In the chromatography, mixtures are separated according to the different solubilities.

In our lab, we used paper chromatography and water to separate food colouring mixture, green colouring mixture,and unknown mixture. Water carries mixture up a strip of paper, then we measure the length of solvent front(d2) and solute front (d1). We divide d1 by d2 to get ratio of fronts(Rf)

October 18 -- Ahmad Kilani

Methods of separating solutions/mixtures:

on Friday, we were introduced to a new subject of chemistry, which is the different methods of separating mixtures or solutions.  We took some notes on the subject and then had time to review for our test on Thursday a little bit.

Here are some pictures and videos that would help explain these methods of separation furthermore:

Filtration

Crystallization

Gravity Separation (Flotation)

Distillation

Simple Chromatography

October 14th Blog By Greg Sra

       Last class we learned about Acids. Acids are formed when a compound composed of Hydrogen Ions and a negatively charged ion are dissolved in water. The ions separate once dissolved in water.

Naming Acids

1) Use "Hydro" at the beginning.

2) The Last syllable of the non-metal is dropped and replaced with "-ic"

3) Add Acid to the end to finish off.

Naming Complex Acids

If the compound ends with "-ate"  you replace that with "-ic"

If the compound ends with "-ite" you replace that with "-ous"

Then you write acid at the end to finish off.

Exceptions

If the acid has the root Sulfur or Phosphorus the ending is "-ic" 

H2SO4(aq) Is Sulfuric Acid. 

H3PO4(aq) Is Phosphoric Acid. 

Some Examples

• HCH3COO Is             Acetic Acid (Vinegar)
• HF  Is                         Hydrofluoric Acid.
• HBr Is                        Hydrobromic Acid.
• HNO3  Is                     Nitrous Acid.
  

OCTOBER 7 -- MARCUS LU

OVERVIEW OF MATERIAL LEARNED IN CLASS
- Ionic Compounds
- Covalent Compounds
- Greek prefixes
- Balancing Equations




IONIC COMPOUNDS =
Two or more particles held together by electrostatic forces.  Consists of a metal and a non-metal

COVALENT COMPOUNDS=
Consists of a non-metal and another non-metal, that share electrons.  When writing COVALENT COMPOUNDS we use greek prefixes to represent the number of particles in the compound.

GREEK NUMBERS=
mono-1
di-2
tri-3
tetra-4
penta-5
hexa-6
hepta-7
octa-8
non-9
deca-10

HOW TO BALANCE EQUATIONS:
If you still havn't learned how to balance equations throughout science 8,9, and 10, check out this website which shows you in great detail how to balance equations. http://richardbowles.tripod.com/chemistry/balance.htm

October 5th-- Nick Kim

 Today we did our second lab, it was about heating and cooling of dodecanoic acid. what we try to find out in this lab was, what temperature makes solid dodecanoic aid into liquid and what temperature makes liquid temperature in to solid again.

 Part1: In heating process

we put test tube(dodecanoic aid) into hot water(55C) , and waited about 7 min, when temperature of the dodecanoic reached little higher than 50C, it melted

 Part 2: cooling process 

 we put test tube(dodecanoic aid, solid) into tap water, and waited about 9 min, when temperature of the dodecanoic reached about 25C it became solid