December 13 Lab Greg Sra

So in todays class we did a lab. The lab consisted of us melting down anhydrous salt in a crucible at finding out how much water evaporated, and what changes occurred during the heating. We found out that once the salt was heated it changed from dark blue colour to green like colour.

Anhydrous Salt

calculating empirical formula of organic compounds

This is the balanced chemical equation for the burning of CxHy

CxHy + 2 O2 -> CO2 + y/2 H20

We need to find x and y, which is the amount of moles of C in CO2 and H in H20

We are trying to find the empirical formula of a compound that burns to produce 16.9 g of CO2 and 3.46 grams of H20.

First, convert the mass ( grams)  of CO2 and H20 into moles.  You should get 0.384 moles of CO2 and 0.192 moles of H20

Secondly, we need to find out how many moles of C are in CO2 and how many moles of H are in H20.   There are 0.384 moles of carbon and hydrogen.  Because they are the same number, when you divide them you get 1. So, the empirical formula is CH.

There are review sheets with plenty of questions for you to practice.  There is a quiz next class.  Here are some videos with empirical formula and molecular formula

Percentages - Ahmad Kilani

Brief Summary:

So percentages are how much each element represent of the whole compount by mass.  Like H2O for example, has 88.9% oxygen, and 11.1% hydrogen.

Example:

- octane has a molar mass of 114g/mol... 96g/mol is carbon and 18g/mol is hydrogen:

(96/114) x 100% = 84.2% Carbon
(18/114) x 100% = 15.8% Hydrogen

December 1st- Nick Kim

 Today we have learned about empirical formula and molecular formula.
First empirical formula is the simplest whole number ratio of  atoms present in compound

How do we get empirical formula?
In order to find empirical formula we need to follow few steps
Let just say you have a compound containing 40% carbon, 53.3% oxygen and 6.7% hydrogen by mass

1,Start with the number of grams of each element, given in the problem. 

If percentages are given, assume that the total mass is 100 grams so that 
the mass of each element = the percent given.

Thus, 40% of carbon is 40g of carbon, and same process for all other elements
40g of carbon
53.3g of oxygen
6.7g of hydrogen

2,Convert the mass of each element to moles using the molar mass from the periodic table
(we have learned  molar conversion last week)
40g of carbon x 1mole/12.0g = 3.3333....... mole of carbon
53.3g of oxygen x 1mole/16.0g= 3.33125 mole of oxygen
6.7g of hydrogen x 1mole/1.0g= 6.7 mole of hydrogen

3,Divide each mole value by the smallest number of moles calculated.
3.3333....... mole of carbon
3.33125 mole of oxygen-smallest
6.7 mole of hydrogen

3.3333....... /3.3333....... =1
3.33125 /3.3333....... =1
6.7/3.3333....... =2

4,Round to the nearest whole number, if number is decimal or fraction.  This is the mole ratio of the elements and is  represented by subscripts in the empirical formula.

Empirical formula: CH2O

here is some practice questions
1, A compound was analyzed and found to contain 13.5 g Ca, 10.8 g O, and 0.675 g H.  What is the empirical formula of the compound?
answer: Ca(OH)2

2,NutraSweet is 57.14% C, 6.16% H, 9.52% N, and 27.18% O.  Calculate the empirical formula of NutraSweet and find the molecular formula.  (The molar mass of NutraSweet is 294.30 g/mol)
answer: C14H18N2O5

Molecular formula
Molecular formula is a multiple of the empirical formula and shows th actual number of atoms that combine to form a molecule

molecular formula= molar mass of the compound/molar mass of the empirical formula

Molar mass of the compund: usually this number is given
Molar mass of the empirical formula: need to use the method that is above

Ex, Molecular formula of a compound is 92.0 g/mol and there are 40g of carbon,53.3g of oxygen and 6.7g of hydrogen

First you need to get emirical formula
do same thing as above information

40g of carbon x 1mole/12.0g = 3.3333....... mole of carbon
53.3g of oxygen x 1mole/16.0g= 3.33125 mole of oxygen
6.7g of hydrogen x 1mole/1.0g= 6.7 mole of hydrogen

3.3333....... mole of carbon
3.33125 mole of oxygen-smallest
6.7 mole of hydrogen

3.3333....... /3.3333....... =1
3.33125 /3.3333....... =1
6.7/3.3333....... =2

Empirical formula: CH2O
 To get molar mass, we simply need to look at periodic table
12.0+(1.0)2+6.0
=20.0g/mol

back to furmula
molar mass of the compound/molar mass of the empirical formula
92.0 g/mol/20.0g/mol
=4.6
4.6(CH20)
usually there arent decimal. Sorry lol

here are some videoes that will help
http://www.youtube.com/watch?v=r2Log6-voWo
http://www.youtube.com/watch?v=nslC7lOSc7Y

November 23 Greg Sra

Today we learned about harder mole conversions. First off you have to start with a mole map.

GRAMS --> <--Use Molar Mass <----> Moles --> <--Avogadro's Number --> Molecules
(6.022 * 10^23)
So if you want to go from Molecules to moles you would divide by 6.022 * 10^23. Grams to moles you multiply by 1mol/Molar Mass in Grams

Random Joke of the Day. How much does Avagadro exaggerate? He makes mountains out of mole hills.
http://misterguch.brinkster.net/molecalculations.html
A website to help you with mole conversions!

 

NOVEMBER 17- MARCCCUS LU

MOLES

CHAPTER 4 ---- THE MOLE

Molar Mass is a unit of measurement.  A mole is anything that has the same particle number as 12.00 grams of carbon.  The number of particles is Avogardo's number :  6.02 X 10^23.

TO find the molar mass of a substance, you use a periodic table to find the atomic mass underneath the name of the substance, and write it in grams per mole

EX:  1 mole of oxygen = 16.0 grams per mole

 1 mole of potassium= 39.1 grams/ mole

REMEMBER: The number of particles in 1 mole of any substance is 6.022 X 10^23 particles/mol

November 19th -Nick kim

Mole conversion  

A

-converting atoms,particles,molecules,and formula units into moles(6.022x 10²³)

#  6.022x 10²³ particles,atoms,molecules,and formula units = 1 mole

Ex 4.56x 10⁴³ baron particles into moles

4.56x 10⁴³ particles x 1mole/6.022x 10²³ particles

4.56x 10⁴³/6.022x 10²³ =0.757x 10

                                                  = 7.57x 10²¹

B

-converting moles into grams                                

# In each elements in periodic table, they all have atomic mass

Eg. Fluorine=19.0 Chlorine=35.5 .........
units are g/mol, it means there are 6.022x 10²³ (mol) atoms for one element and they are measure in gram. Therefore, Fluorine has mass of 19.0g/mol 

Ex, 4.01 moles sillicon(28.1g/mol) into grams
4.01moles x 28.1g/mole
4.01 x 28.1=113 g

here is website that will help

http://www.youtube.com/watch?v=ehepBBtSbDc

http://www.youtube.com/watch?v=NMdN1LtHuDA

November 9th Greg Sra

Last class we created a graph about a sample of gas heated in a expandable container. We also got back our quiz's, and have a test next class for Chapter 3.

Chapter 3 Test
On it will be: Sig Figs, Measurement & Uncertainty, Density, Graphing, and Lab 2e.

Random Chemistry Joke of the Day:  A neutron walks into a bar. He asks for a beer. The bartender looks at him ,and says for you No Charge.

Friday November 5 ---- Marcus Lu

Wrote quiz today on aluminum foil lab.  It is required for you to know the Density formuila ( density = mass/volume)  and Volume = L x W x H.

We learned how to make graphs on microsoft excel to express our data.

November 4-NIck kim

 For today, we did our lab on determining aluminum foil's thickness. It was easy and fun lab, we ever had. In order to find thinkness(height) first we needed to know it's length,width,and weight, since aluminum foil is really thin it hard to measure without specalized tool, so we need to use math to find it

when we found out the length,width, and weight. we need to put them in to equation.(density is given)

Formula

 Density(cm3/g)=Gram(g)/volume(cm3)

#volume is equal to (length)(width)(height)

and let height represent x

For example, length:16.80cm width:14.85cm height:x density:2.70g/cm3 gram:1.00

2.70cm3/g=1.00g/(16.80cm)(14.85cm)x
2.70cm3/g=1.00g/249.48x
1.00g/2.70cm3/g(249.48cm2)=x(thinkness)
therefore   x=0.0015cm

In this lab we have practiced how to use density formula

Here is website that help how to get thickness of aluminum foil
http://www.mefeedia.com/watch/29045208

November 2 -- Ahmad Kilani

So last day we were introduced to a new unit; DENSITY:

So density is basically a unit of calculating mass per volume such as g/L (grams per liter) or pounds/cm3... here's a sample of densities:

From small to big.

So basically, the less dense an object is, then that means it floats on a denser object. Here's a video to demonstrate that:

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.

September 29th Blog Entry By Greg Sra

In today's class we learned about matter, physical and chemical changes and did a laboratory assignment on Physical and Chemical changes. We were also assigned a Laboratory Report.



Matter: Is anything made of atoms or particles. (Basically everything around you)

Physical Change: A physical change doesn't have any change in the chemical composition. A physical change occurs when the physical properties are changed. An indication that a physical change has occurred  is if there is a change in: texture, shape, density, volume, mass, and weight.  An example of this is a hockey stick. It is still composed of wood and has the same wood properties. The only thing changed is the physical appearance which is a physical property.

A  piece of wood turning into a hockey stick is an example of a Physical Change

Chemical Change: A chemical change occurs when the product undergoes a chemical reaction thus changing the chemical composition. An indication that this is happening is if the product starts: changing colours or bubbling.  Examples of this include: vegetables spoiling, fermentation, a metal rusting, and photosynthesis. A link to a video about Chemical and Physical Changes

SEPTEMBER 27 -- MARCUS LU

Overview of Material covered in class:
- Matter. What is it?

- Physical and Chemical changes

- properties of solids, gasses, liquids

- Quiz on unit conversions

Notes:  

- Matter:  

Matter is everything that has mass and takes up space ( volume ) . There are two types of matter , PURE SUBSTANCES, and MIXTURES. 

- Physical Change

a physical change is a change where no new substance is formed.  These types of changes are also reversible

-Chemical Change

a chemical change is a change in which a new substance is produced.  These types of changes are irreversible

SOLIDS: solids do not change shape very easily.  They have little change when exposed to heat

LIQUIDS: Liquids take the shape of their container, and change slightly under heat

GASSES:  Gasses take the shape of their container, and drastically change when heated.

September 23

Today we reviewed and  had a practice quiz on unit conversions with quantities and scientific notation . Unit such as gram(g), meter(m), liter(L), and second(s) can be convert it into Tera, Giga,and etc...                    For example, Tera gram, Giga meter, or Milli second.





How to convert unit
For example, if you want to convert 4 m into mega meter, then first you should know how big mega meter is. At left chart, it said Giga is 10⁹   greater
than meter. So, equation should be.....................4m×Gm/10⁹m
Always unit that you want to convert into should
be at the top of fraction and unit you want to get
rid of should be at the bottom. meters cancel ea-
ch other out ( meter divide by meter is nothing)
then equation becomes.....................................
4×Gm/10⁹ right? then 4 times Gm is 4 Gm
and  now you have the answer 4Gm/10⁹
or 4Gm/10000000000 or 0.000000004

But writing 0.000000004 Gm is too long, so 
we use scientific notation 
0.000000004 Gm is 4×10⁹  Gm in scientific
notation. When you actually
calculate 4×10⁹ 
Gm is same as 0.000000004 Gm. But it just
shorter

posted by Nick kim

SEPTEMBER 21

FIRST POST OF THE YEAR !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!  Today we learned about Scientific Notation, and received some wonderful worksheets to practice our skills at converting units.  There is a quiz on Monday on Converting units.