Absolute Uncertainty a.k.a Uncertainty

    Today we learned about a very very interesting things called.....PRECISION, ACCURACY, AND ABSOLUTE + RELATIVE UNCERTAINTY.  Notice it is in CAPS, it means that its very important.

Precision = is how reproducible a measurement is compared to other similar measurements

Accuracy = Is how close the measurement comes to the accepted or real value

(If you could use definitions then so can I)

For example if you the real value is 10 cm.  If you measured 9.7cm  then it is accurate however if it is like 50cm then its not very accurate.   If you repeatedly measure and get the results of 9.8cm, 9.8cm, 9.9cm, 9.8cm then it is precise since the results can be reproduced.  BUT if you are very bright and smarter than the average lad and measure 4cm, 9.7cm, over 9000cm then it is not precise but 9.7 is considered accurate unless you take all the numbers into account for average measurement then it is neither accurate or precise.  If you dont understand read it over 50 times. 

Then the next thing under CAPS is ABSOLUTE UNCERTAINTY.  Im absolutely sure it would mean the same thing if absolute uncertainty is uncertainty but adding absolute made it sound more scientific.  Anyway onto absolute uncertainty.  Everything that is measured IS NEVER EVER EVER EVER NEVER EVER EVER NEVER EVER EVER exact ( except things you can count like human beings though you could be half of a person but that is debatable)  There ALWAYS be a degree of some uncertainty.  And we learned how to calculate the uncertainty below. 

 If you are not bored and didnt exit out of this site then read below then exit out of the site. HF

there are 2 ways to calculate uncertainty but know this, it is always expressed in the units of measurements such as M, cm, etc and never in a ratio.

METHOD 1: THE MATH METHOD

Make measurements (the more the better) and take out any data that looks off or your sure you measured wrong then calculate the avg.  The absolute uncertainty is the greatest difference between the avg of the measurements and one of the measurements you made that are REASONABLE.

Trial                               Mass of a Swift Scout Holding 3 Mushrooms(kg)

  1                                                  20

  2                                                  19

  3                                                  20

  4                                                over 9000

  5                                                  20

First you take the most unreasonable one.  I would say the 20 but i am forced to take away over 9000 eventhough it seems most reasonable.  Then you take the average of the numbers left over.  The average is 19.75.  Then you find the greatest difference with the reasonable measurement which would be 19.75-19 = 0.75.  Then you write the answer like this.  The mass of the swift scout holding 3 mushrooms is 19.75kg plus or minus 0.75kg.  As long as the mushrooms dont blow up, your answer will be relatively correct.

METHOD 2: THE OTHER MATH WAY

 uncertainty of instruments =  Uncertianty of instruments that measure stuff

This is SUPER SUPER SUPER SUPER SUPER SUPER SUPER EASY.  You take the smallest segment on your instrument and times it by 0.1 and that is your uncertainty for the instrument.

Relative uncertainty = ABSOLUTE UNCERTAINTY/ESTIMATED MEASUREMENT

 basicly using the data you have into the formula above

it can be expressed in % or sig figs your choice.   BTW the number of sig figs indicates relative uncertainty



Significant Digits, Exact Numbers, Rounding and Operations

Let's say your're driving across the country in your Dodge Caravan, or Honda Civic if you want to promote the stereotype, and you come across a sign that says, "Entering Awesometown, population: 271,835". This figure is most likely COMPLETELY AND UTTERLY INCORRECT. But what if the sign said, "Entering Awesometown, population: 270,000". This figure is not entirely incorrect. By applying significant digits, this sign has become 68% more reliable.

A precise less precise number like 270,000 implies that the zeros are subject to change, whereas a number like 271,835 implies that the digits are there and cannot change and in most situations when dealing with inconsistent numbers like population, these precise numbers are incorrect.

HOWEVER, Significant digits or Significant figures or if you want to be super cool, Sig-Figs must be measured and have at least some certainty. The rule is that the last sig-fig in a number is uncertain while all other sig-figs are certain.

Ex. 5486; digits 5, 4 and 8 are certain while 6 is not

But how does one know which which digits are significant? Well, I have devised a set or rules, or commandments if you will for telling which digits are significant.

THE 5 COMMANDMENTS OF SIGNIFICANT DIGITS:

COMMANDMENT 1) All non-zero digits ARE significant.
ex. 7.342 has 4 Sig-Figs

COMMANDMENT 2) Zeros that trail after Sig-Figs and are before the decimal ARE NOT significant.
ex. 1340000 has 3 Sig-Figs

COMMANDMENT 3) Zeros that trail after the decimal point ARE significant.
ex. 54.00 has 4 Sig-Figs

COMMANDMENT 4) Zeros that come before Sig-Figs ARE NOT significant.
ex. 0.000078 has 2 Sig-Figs

COMMANDMENT 5) Zeros between other Sig-Figs are ARE significant.
ex. 5400.045 has 7 Sig-Figs

Exact Numbers


Some numbers have a set value assigned to certain things. One human has a set value of 1, if the subject is how many humans. We cannot say that there are 3.5 humans unless we were able to find 3 humans and half of one. If 3.5 humans were somehow calculated it would be rounded down to 3 humans.

Rounding

you will need to know your general place values, refer to this chart

If you have calculated an ugly answer such as 6542.5865 and you can only keep 2 significant digits, you must round your answer to accomplish this.

To do so, follow the basic rounding rules:

Look to the digit to the right of the desired place value that you want to round your answer to. If that number is larger than 5 round up and vice-versa. Simple, right? BUT WHAT IF THE NUMBER IS 5?!?!?!?!

CALM DOWN, BUDDY. First look to see if there are numbers after the 5. If so, round up because that indicates that the number is larger. If not, and the number is 5, this means that the number is exactly half-way, in which case, rounding it up wouldn't really be more correct or more incorrect than if you rounded it down. However, if you have a set of digits, you wouldn't want your data to be rounded up more than down. Round to the nearest even, or in other words, if the digit to the left of 5 is odd, round up, if it is even, round down.

Operations with Significant Digits

Addition and Subtraction:

line up your numbers like you would if you were doing old-school math, pre-calculator style with the decimals lined together.

    779.233

+   68.4    

    710.833

Examine the numbers: 779.233 goes to the thousandths place while 68.4 goes the the tenths place. ALWAYS PICK THE LOWER ONE. Round your answer to the tenths place. 710.8. Same rule applies for subtraction.

Multiplication and Division

44.56 * 846651.243 = 37726779.38808

Again examine your numbers and again, choose the lower one. This time, notice the number of sig-figs in each number. 44.56 has 4 while 846651.243 has 9. Round your answer to 4 sig-figs. 3773. Same rules applies for division.

SO THE CONCEPT IS: Lower amount of sig-figs means more reliable, because it reduces the chances of being COMPLETELY AND UTTERELY INCORRECT.

TL;DR: Watch this vid of Mr.Coolteacherguy with the pro hair talk about Sig-Figs.

Another fun and exciting lab~

Today we did another lab to see how to separate solutions in full action. At first Ms Chen told us to get all the equiptments that we need then we all had to WEAR OUR SAFETY GOGGLES ( Always have safe even when we are dealing with food dye. There might be a chance for it to accidentally color our eyes). As we moved on with the lab we all had 3 pieces of paper and we had to cut the piece of paper in to a pencil shape. Then with a pencil we marked a line 4 cm from the tip. Then the fun part begins we filled the test tubes with 2 cm of water and got a drop of food dye with the color of our choice (red yellow blue, BLUE FTW!!!) from Ms Chen. We put the chromatograph with a dot from the food dye into the test tubes. When we are finish the food coloring that Ms Chen give us we had to record it on the board and get new colors (Unknown and green) from the back.


After 20 minutes the food dye finish separating and the end results is food coloring that have been separated into it original colors.  After we pretty spent the rest of the time doing the lab questions...

Separation Techniques

This class we learned about separating mixtures.

Since components keep their identities, you can devise a process that discriminates between components with different properties. There properties include:

-Density                                     -Reactiveness
-Volatility                                   -Magnetic/non-magnetic
-Solubility                                  -Polarity

Here are some basic separation techniques:

Filtration: select components by particle size through a filter

Floatation: by density

Distillation: by boiling points

Chromatography: by attraction for a stationary phase

Hand Separation: (solids and solids): A mechanical mixture/heterogenous misture can be separated by a magnet or a sieve(sifter)

Evaporation: (solid dissolved in a liquid solution): boils away the liquid and leaves the solid behind.

Here is how each process works:

Filtration:(undissolved solids and liquid): Passes a mixture that contains solid particles through a porous filter. If the pores are smaller than the particles, then the solid particles stay on the filter.

Crystallization: (solid and liquid) A saturated solution of a desired solid is used. Which is then turned into a precipitate through chemical or physical change. The solids are then separated by floatation or by filtration. The liquid is then evaporated or cooled and the solids come out as pure crystals.

Gravity Separation:(solids based on density) A centrifuge whirls a test tube at high speeds forcing denser materials to the bottom. This works best with small quantities.

Solvent Extraction: A component movies into a solvent shaken with the mixture. Works best with one component that dissolves.

          Mechanical Mixture: (solid and solid): liquid to dissolve one solid but not the other, so the desired solid is lieft behind or dissolved
 
         Solution: solvent is insoluble with solvent already present. The solvent dissolves one or more substances and leaves the unwanted behind.

Distillations(liquid in liquid solution): Distillation is collecting and condensing volatilized components. Heating a mixture can cause low-boiling components to vapourize. The component that boils evaporates and enters a condenster; the gas the ncools and condenses back into liquid dropping as a purified liquid.

exmaple of distillation

Chromatography: There are many different types of chromatography and they include both the mobile and stationary phase. It is highly accurate and precise with its analyses and it is used to separate very complex mixtures (for eg. drugs, plastics, foods, pesticides). Then the separated components can be collected individually.

Sheet Chromatography: Paper Chromatography (PC) involves a strip of paper. The solvent is applied on the strip of paper and then the components appear as separate spots spread out on the paper.

Now for an example of paper chromatography:

OMG ANOTHER SUPER SUPER FUN CLASS!!! YAY!!!!

OMG OMG OMG OMG OMG TODAY WE LEARNED ABSOLUTELY THE MOST FUN AND SUPER COOL THING EVER LEARNED IN CHEMISTRY....NAMING STUFF! OMG I KNOW!

First of all we learned what an acid is.  An acid is formed when a compound composed of hydrogen ions and a negatively charged ion are dissolved in water.  Ions separate when dissolved in water? I know so super cool.

ex. H + CL = HCL ---- HCL + H20-->H30 + CL         H ion joins with H20 to form H30


Now the super super fun part and the main super super fun thing we learned....NAMING

First of all we learned how to name SIMPLE acids and they follow the following super cool rule:

1.Use "hydro" as the beginning
2.Last syllable of the non-metal is dropped and replaced with "-ic"
3.Add "acid" at the end

should be like this        ____ide ---> hydro_____ic acid

these are some examples

1. HCL ---- Hydrochloric acid   2.H2F ------ Hydrofluoric acid   3. HBR ----- Hydrobromic acid  

Hydrocloric Acid

Now to name the super super complex chemicals. =) its so fun.

We take the compounds at the back of the sheet and apply the following totally super awesome rule

1. Replace the "ate" ending with "ic" or

    Replace the "ite" ending with "ous"

Ignore label. It is actually
Acetic Acid

2. Put acid at the end of the name

these are some examples

1.HCH3COO --- Acetic acid aka vinegar (trolololol)   2.HCL03 --- Chloric acid  3.HNO2 --- Nitrous Acid

4.HCLO4 --- Perchloric acid

   

Then the TOTALLY BEST part of class is that we got a worksheet. The worksheet TOTALLY DID NOT have a lot of questions and was TOTALLY FUN.  SO FUN in fact that I am so hyped up talking about it.  Who doesnt like doing 100 questions? Work is sooooooooooooooooooooooooooooo fun.  This concludes my totally super super fun blog about this super super fun day......Yay...until next time...yay.



As you may recall, in our previous class, we did a lab. This class was basically split in to 2 sections. First we continued with our lab report and write up. My partner and I ran around the class looking for two other groups to compare with. Eventually, Ms. Chen stopped the absolute madness and commenced the lesson.

Writing and Naming Ionic and Covalent Bonds!


"Wait a minute! That's sounds somehow oddly familiar... didn't we cover the same subject in grade 9 and 10?"
"That's right Billy, and now we get to learn it AGAIN!!"
"Golly gee wilikers, what fun! I sure hope we get a whole bunch of redundant practice problems!
"197 of them, in fact!"
"HOOORRAYY ADVENTURE HO!!!!"

Ionic compounds
metal + non-metal (oppositely charged)
electrons from metal transfer to non-metal
Symbol: Criss cross apple sauce the charges, 1's need not write and simplify if possible

Ex.

Li¹⁺ + O^2---> Li₂O

Zr⁴⁺ + S^2- --> Zr₂S₄ --> ZrS₂

Name: write out metal name, then non-metal name but with "ide".
Ex.
calcium + chlorine ---> calcium chloride

Usually metals near the middle of the periodic table. In this case, include the number of the charge being used in a roman numeral.
Ni²⁺ + Br --> nickel (II) bromide
Ni³⁺ + Br --> nickel (III) bromide

Back in the day, they would use "ic" to represent 2+ and ous to represent 1+ charge. For charges higher than 2, "ic" would represent the higher one while "ous" the lower one.
Ex.
Cupric = 2+
Cuprous = 1+

A common ionic compound, NaCl, sodium chloride or better known as salt.

Covalent Compounds

Unlike ionic compounds, covalent compounds share electrons and combine non-metals with non-metals
Naming: Greek prefixes must be put in front of elements according to their charge.
1 - mono
2 - di
3 - tri
4 - tetra
5 - penta
6 - hexa
7 - hepta
8 - octa
9 - nona
10 - deca

Ex.
P₄O₃ --> tetraphosphorus trioxide
*Mono for the first element need not be written
CO₂ --> carbon dioxide

Diatomics: certain elements can combine with another of themselves
H₂ O₂ F₂ Br₂ I₂ N₂ Cl₂ Hofbrincl

Carbon dioxide can be found in our atmosphere. It is debatable whether it contributes to global warming.

Polyatomics
Groups of ions form together as one atom. Naming is simply writing the two compounds/elements involved
Symbol: When criss-crossing, brackets must be put if there is an existing subscript.
Ex.
Calcium Nitrite --> Ca²⁺ + PO₄^3- --> Ca₃(PO₄)₂


For the rest of the class we finished our lab reports.

The polyatomic citric acid (C₆H₈O₇₎ is used in orange juice

Lab number 2 ~ Exploring the process of heating and cooling

Hmm After a whole month of waiting, we FINALLY did a more interesting lab Observing the cooling and heating of Dodeconoic acid. First what is Dodeconoic acid? When we smelled it felt like it is some really dangerous stuff but Dodeconoic acid is just some coconut oil... haha I should of expected it to be something really house hold. So basically we could of drank some of those acid and still be perfectly okay. Each group had 2 people one looking at the thermometer every 30 sec and the other recording the readings.

This is the chemical compound of Dodecanoic acid

Of course we started our lab with safety glasses (Safety First) and as Ms Chen went over what we need to get we quickly started our lab. At first we have to cool the Acid because the class before us have already heated the acid to 50C. We got a beaker of cold water and placed the Acid solution inside. As minutes go by a thin layer of white stuff formed on the thermometer. Then as the temperature went down the whole solution become a white solid (Just in case the coconut acid explode we all wore safety glasses for the whole time) which was pretty amazing to some of our classmates... but to me, who have seen like everything, it just looked like another wonder of nature. I asume the process of cooling went pretty well with everyone in the class because most people moved on to heating at about the same time.

Heating also didn't seem like much trouble, we got our hot water from ms Chen with our beaker. Well all we really did was to put the acid solution back in the water and let the magic happen. We had to wait untill the acid is heated back to 50C. I though the heating of the acid was a lot faster than the cooling probably because we had really hot water.

Awhile later we all cleaned up and started on our lab report and graphs.

That was pretty much our day~ and next class we are going to finish our graphs and lab report.

The Heating/Cooling Curve of a Pure Substance

This class' lesson was on the Heating/Cooling curve of a pure substance. Each point on the graph represents a pure substance changing into a new state.


A
-solid state at any temperature below its melting point
-particles packed closely together
-can only vibrate in a fixed position
A-B
-heat energy turns to kinetic energy when heated
-molecules vibrate faster
-temperature increases
B  

-still a solid
-temperature remains the same
B-C
-exists in both solid and liquid state
-temperature remains constant
-contant temperature = melting point
C
-substance has completely melted
-solid has turned into liquid
C-D
-liquid state
-increasing temperature gives heat energy
-particles move faster
D
-exists in liquid state
-molecules start to move freely
-liquid beings to change into gas
D-E
-exists in both liquid and gaseous state
-the temperature remains unchanged
which is the boiling point
E
-liquid has turned into gas
E-F
-gas particles continue to move faster
-temperature increases as heating continues

NOW IT'S TIME FOR SOME TEXTBOOK SUMMARIES!!!!

Finding Out about Matter

Chemists specialize in one of the most important things, matter. So we ask ourselves

• How does one type of matter differ from another?
• What different types of matter have in common
• How one kind can be changed into another or even kept the same

 That is why chemists require unique abilities to make the most detailed observations and analyses.

What YOU Know about Matter

Water is one of the most familar kinds of matter. It's all around us but is it all the same? It acutally comes in all different kinds of forms and types. Water can actually come as a solid, liquid, and even a gas.
If you compare muddy water and water from an ocean, you observe that they look totally different. This is because they are and they both  have different characteristics. Water from different sources can have different tastes and different boiling points.  A boiling point is a temperature in which matter changed from a liquid to a solid.

Purifying Matter

Have you ever noticed that a cup of muddy water continas more than just water? This is called a mixture which are two or more kinds of matter that have separate identities. Matter can be in the form of a mixture or a pure substance. A pure substance is just one kind of matter. In some cases, adding things to pure water like sugar or salt just disappears and does not scatter light. These are called solutions. We know that they taste different but we cannot distinguish if the material is pure from the looks of it.
To find the difference between these two, tests are to be run. They are not ordinary tests, they are tests that separate components. You might ask yourself, how do we do that? It's called distillation; a procedure that evaporates the liquid and leaves produce behind.

Characteristics of a Pure Substance

Pure substances have a constant boiling point and mixures do not.
The temperature at which a liquid changes into a solid is called a Freezing Point
The temperature at which a solid changes into a liquid is called a Melting Point



Chemical and Physical Changes

From the previous posts, we have distinguished the difference between physical and chemicals changes.
Chemical change is irreversible and produce a new kind of matter with different properties.

• This is called decomposition because one kind of matter comes apart to form two or more kinds of matter.

Physical change is reversible and do not appear to produce new kinds of matter.


Compounds and Elements

Electrolysis involves passing an electric current through a substance, causing it to decompose into new kinds of matter
Compounds are pure substances that can be decomposed into new kinds of matter
Elements are pure substances that cannot be decomposed.

Compounds Have a Definite Composition

First of all, there are 2 important rules about compounds

Law of Definite CompositionThis states that all compounds can have any possible composition, but the composition of the compounds must remain the same

Law of Multiple PropertiesThis states different compounds can be made with different amounts of the same elements.