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

The Only Thing Constant in Life is Change -- by Ria Park

Marcroscopic

- physical objects that are measurable and can be seen just by eyes


Physical Change
- a solid is formed
- heat is produced(e.g. if we band a copper string, the part that is banded is getting hotter.)
- a liquid is fromed
- change in shape

Chemical Change
- change in colour
- a gas is formed
- change in odor
- a solid is formed
- heat is produced
- a liquid is formed
- light is produced


These are the macroscopic behaviors that we could observe from today's lab.


This is the table that we did.

Change You Can Believe In --- By Nemo Jin, Sally Chen

Physical Change

Description:

---Physical changes occurs when the state of matter changes, or two substance physically combine together.

---No new substance is being produced.

Three states of matter:

Solid: 

        --Particles are packed together tightly. They can only vibrate within a certain area.

Liquid:

        --Particles can move around. The shape of a liquid is determined by its container. The volume of a liquid depends on temperature and pressure.

Gas:

        --Particles are able to move around freely at a high speed. They are separated with no regular shape.

Chemical Change

Description

-- New substances are being produced.

-- Changes in composition of a substance.

-- Color changes; odor changes;energy is released (light, heat)

-- Atoms are rearranged in chemical changes.

                                                          

Chemical Changes

Synthesis; is when simpler reactants combine together to make a compound. Ex; the picture below, showing that the N2 and 2O2 combine together to make 2NO2.

Combustion; is when only the atom arrangement changes. Ex; picture below only shows that the arrangement of the atoms changes. They didn’t break down or anything.

Decomposition; is when a reactant breaks into simpler reactants. Ex; picture at below, the 2H2O breaks into 2H2O + O2.  

Pictures provided by Fadhila Science-Stuff