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

October 1 -- Ahmad Kilani

In class we got our quizzes back, took a few notes, and finished a sheet  about matter and it's states.  We also got some time in class to finish reading pages 25-34, 36, 39 in the textbook, make a flowchart, and write a pre-lab report.

Summary of pages in the textbook

 - There's a difference between solutions and mixtures.  In mixtures such as water and mud, you can usually see light scattered if it passed through the mixture, but if you pass light through a mixture such as water and salt, or water and sugar, the light doesn't scatter which makes it harder to spot if it's pure or impure.  These mixtures are known as solutions.  Some solutions can be separated by a process called distillation, while other solutions cannot be separated by distillation such as water and grain alcohol because the whole mixture has the same boiling point.

Heating a pure substance.

Cooling a pure substance.

 - When heating a pure substance (such as pure water), the substance keeps increasing in temperature until it starts boiling, and when it does start boiling, the temperature stays constant.  But with a mixture such as 75% water and 25% methanol, the mixture's temperature increases faster than the water, until it reaches 86 degrees, and when it does, the temperature doesn't stay constant, it keeps increasing but at a lower rate, and vise versa with cooling/freezing.

- Sometimes heating a substance doesn't necessarily mean that physical changes occur.  If you heat sucrose for example, the heated sugar turns into a completely new substance that has nothing to do with sugar, and there is no way to return it back to sugar, which means that it's a chemical reaction occurred instead.

 - If you put a light bulb with negative and positive terminals in solid salt so that it transfers electicity to the bulb, no electricity will reach the bulb.  But if you place the terminals in liquid salt, then the light turns on!  That is because the liquid salt conducts electricity, while the solid doesn't.  Also, if you leave the battery on, the liquid would start turning into a gas (chlorine) and a silvery liquid (sodium) which is known as electrolysis.  The same thing can be done with water, but the process is a little slower.

Here is a list of all the new terms learned:

- Boiling Point: the temperature at which matter changes from liquid to a gas.
- Melting Point:  the temperature at which a solid becomes a liquid.
- Freezing Point:  the temperature at which a liquid changes to a solid.
- Mixture:  two (or more) kinds of matter that have separate identities.
- Solution:  a homogeneous mixture of two or more substances frequently (but not necessarily) a liquid.
- Distillation:  a process of purifying a liquid by boiling it and condensing its vapors
- Density:  is a property of matter that describes its mass per unit volume.
- Chemical Change:  changes that produce a new kind of matter with different properties.
- Physical Change:  a change in matter where no new substance is formed.
- Decomposition:  process where one kind of matter comes apart to form two or more kinds of matter.
- Electrolysis:  it involves passing an electric current through a substace, causing it to decompose into new kinds of matter.
- Compounds:  pure substances that can be decomposed into new kinds of matter.
- Elements:  elemental building blocks of all kinds of matter.