Oct 26, Significant Digits

After the test that I have failed, today we have learned significant digits.

Significant Digits(Figures)
-The last digit in a measurement is uncertain.
-Trailing zeros after the decimal point are counted
-Leading zeros aren't counted
-Trailing zeros without a decimal point aren't counted

Example : 2.567 = 4 significant digits
               0.0097 = 2 significant digits
               10000 = 1 significant digits
               10000. = 5 significant digits
Exact Numbers
-Same quantities are defined as exactly a certain amount and no rounding is required and have infinite significant digits
 Ex. Number of people, animals, items etc
Rounding Rules
-if the number you are rounding from is greater than 5 you round up
-if the number you are rounding from is smaller than 5 you keep the number in front
-when the number you are rounding to is 5 then:
                 -if the number you are rounding from is 5, round to make the last digit even
                 -if the number you are rounding from isn't 5 then you round up
Example:
     Rounding to the tenth
1.01 = 1.0
1.06 = 1.1
1.00 = 1.0
4.95493 = 5.0
4.85493 = 4.8
1.05 = 1.1

October 19 2010 - Experiment 3B

Today, we did our third experiment yay!  We learned how to separate mixtures through chromatography.

The first thing we did was we had to set up our experiment by getting 3 large test tubes and put them into  Erlenmeyer flasks.  Water was put into each test tube.  We then cut a tip on 3 of the chromatography paper.  We would then have to put a dot of red/yellow/blue on one strip of chromatography paper, we would then dip that into the water in the test tube and wait for the water to come up through the paper.  We did this for 2 other mixtures, green dye and an unknown substance.  We observed and realized that the three substances had separated to a certain degree.

A video to a chromatography experiment

October, 15/10 - Separation of Mixtures and Solution.

The basis of separating mixtures is by separating different components with different properties form each other.
There are nine ways that we will be learning about how separation occurs when separating.


Hand Separation: Evaporation

• Hand separation (solid and solid)
• Mechanical mixtures separated by using magnets or sieves.
• Evaporation
• Boiling the liquid to leave the desired solid.

Filteration

• This method can be used when the solid is not dissolved in the water.
• The mixture passes through the filter and and the solids are stopped by the pores of the filter if the particles are too big to fit through.
• If the pores are bigger than the particles, the particles will pass.

Crystallization

• Precipation in crystallization converts solutes to solid form by chemical or physical change.
• Solids than separate by filteration or floatation. Floatation is when the denser components sink to the bottom.
• Evaporate and then cool and you will get the desired component(s).

Gravity Separation

• Separates particles by density.
• Heavy particles will sink to the bottom. The light particles will rise to the top.

Solvent Extraction

• A component will move into a a solvent and is shaken with mixtures.
• When dealing with mecahnical mixtures ( solid and solid), liquid will be used to dissolve one component.
• When dealing with solutions, the use of liquid will dissolve one or more substance until it leaves the wanted substances all by itself.

Distillation
(liquid and liquid solution)

• Using the boiling method, the liquid with the lowest boiling point will rise and condense first. Then it cools and drops into another container as pure. This may also leave the other substance as pure.

Chromatography

• Sweeping the mixtures, compounds that are heavier will slow down at a point to come to a gradual stop.
• This is a very good method for separating complex mixtures like drugs.
• The separated components can be collected individually.

Sheet CHromatography

• Known as paper chromatography (pc)
• Stationary Phase - components that spent a long time in a place will soak into the paper, leaving spots in a phase more than others.
• The components appear at separate spots ajd spreads when dried (compenents can be collected).

Thin layer Chromatography (TLC)

• Stationary phase - A thin layer of absorbent is coated on a sheet of plastic or glass.
• Some compounds will bond to it stronger than others and will stay on the absorbent. When dried, it can also be collected.  

Naming Acids Oct.13/2010

Today October 13th 2010 wednesday we learned naming acids.

Acids - formed when a compund composed of HYDROGEN ions and a negatively charged ions are dissolved in water which is also called aqueous.
                           - Ions seperate when dissolved in water. Ions with H₂O to form
                           - H⁺ ions with H₂O to form H₃O⁺(H(YDRONIUM ion)

Naming The Acids (Simple Acids)
1. Use "hydro" as the beginning
2. Last syllable of the non-metal is dropeed and replaced with "-ic"
3. Add "acid" at the end

Examples.
HI(aq) - hydroiodic acid
HCl(aq) - hydrochloric acid
H₂S - hydrosulphuric acid

Naming Complex Acids
1. -ate replaces with -ic
    -ite replaces with -ous
2. Acid at the end of the name

Examples.
H₃ClO - chloric acid
HNO₂  - nitrous acid
HCH₃COO - acetic acid

Naming Acid Part.1

Naming Acid Part.2



October 7 2010 - Writing and Naming Ionic and Covalent Compounds

Ionic Compounds
-composed of 2 or more ions (oppositely charged)
-held together by electrostatic forces
-electrons are transfered from metal to non-metals


Writing and naming ionic compounds 


To make an ionic compound, you need to combine a positive and a negative together/ a metal and non-metal. 


Ex.
Na+ (positive) and Cl- (negative) make NaCl


If the charges are different, then you need more ions to balance it.


Ex.
Mg(+2) has a +2 charge, so you need two Cl- to balance it


The result would be MgCl2

Ex.

  NaCl is composed of sodium and chlorine. Na is always 1+, and Cl is always 1-.  Add the charges of the positive ions, and separately add the charges of the negative ions. Each will equal the other.

Look at CaCl2, for example. Ca always has a charge of 2+. Cl again is always 1-. You need two Cl and one Ca to make a neutral formula. Be sure to write the formula for the smallest whole-number ratio for each ion.

When writing the name for the formulas, you just add the prefix -ide to the end of the second element. So NaCl would be sodium chloride. 

The rule is the same for polyatomic ions.  Just put parenthesis around the polyatomic ion to remember that the entire group of atoms is the charge.  For example, nitrate (NO3)-.  the entire polyatomic ion is 1 negative charge.  Or, phosphate, (PO4)-3. This means that the entire polyatomic ion is a 3 negative charge.  When you combine it, use the same rule as if you were combining single ions together. For example: NaNO3 or Na3PO4


When writing out the names of multivalent elements, you use roman numerals after the name.


Ex.
FeO = Iron(II) Oxide


Covalent Compounds

-share electrons
-non-metals with non-metals
-diatomic  molecules= H_2, N_2, O_2, F_2, Cl_2, I_2, Br₂


Writing and naming covalent compounds


To make a covalent compound, usually you need a negative and a negative together/ a non-metal and non-metal.  Writing covalent compounds is the exact same as writing ionic compounds.


When writing the names of the covalent compounds, you must use greek prefixes.  


Ex.
CO2 = Carbon Dioxide


*note* if only one of the element is needed in a covalent compound, the prefix mono is not needed, but it is needed on the second element.


CO = Carbon Monoxide


Ionic and Covalent Bonding video

October 7, 2010

Finding Out About Matter (p.25-34, 36-39)



Everything thats around us in our environment is made of matter. Matter can be broaden into different categories that distinguishes different types of matter from each other. For an example, all substances have a boiling point but at different temperatures. These characteristics can give matter individuality.

Purfying Matter

When different types of matter are put together, they can either form mixtures or solution. So what are mixtures and what are solutions? Mixtures are when two types of matter that mixes together and the mixture is clearly visible such as having sand mixed in water. Solution is when you mix two different types of matter together but you cannot see with the naked eye such as mixing sugar into water. However, the two elements can be separated through the method of distillation. However, some mixtures of matter are more difficult to separate than others and some solutions may be considered as pure substances until an innovative way of distillating them has been discover.

Characteristics of Pure Substances



Ways to determine the charactersitcs of substances include their boiling point, melting point, and freezing point. Through the characteristics, we can tell the difference between on substance and the other. For example, if we boil the solution of salt wate, the temperature gradually rises when the water boils away. On the other hand, if you just boil pure water, you will find that it boils to a point and continue boiling until the water disappears. This means that pure substances have a constant boiling point. Usually, mixtures don't have constant boiling point. However, some mixtures such as water and grain alcohol have a constant boiling point at 78.2 degrees. Melting and freezing points are also charactersitics to be dicussed. Melting point is the point when a specific type of substance melts while freezing point is the point where a specific type of substance freeze due to the low temperature.

Chemical and Physical Changes

There are two types of changes in matter. One is chemical change and the other is physical change. Chemical changes are changes that do not necessarily have to be seen. The change is determine by the release of energy, colour change, and possibly the smell. After a substance undergoes chemical change, it becomes a new substance and usually it cannot change back to its original form. Chemical changes that break down into two or more new substances is called decompostion. Physical change is the change that you can see with the naked eye and no new substance is formed.

Compounds and Elements

Elements are the bases of a specific type of substances. They can combine with another element that is different from themselves to form compounds such as NaCl (salt). A way to separate compounds to form new substances that can be done with electricity is called electrolysis. This method can decompose substances to form new kinds of matter.



Go to: http://www.youtube.com/watch?v=xYFAj50c7xM to learn more.

 

October 5 2010 - Experiment 2B

Today, which is October the 5th.  We did an experiment on the heating and cooling of a pure substance (dodecanoic acid/lauric acid) and watch the changes of it.

We were given a test tube containing dodecanoic acid in liquid state and had a thermometer in it.  We would then have to clamp it into position into a beaker of room temperature water.  We would monitor the cooling process and record its temperature every 30 seconds until the dodecanoic acid reached a temperature near 25 deg. Celsius.  The temperature would be recorded every 30 seconds.  After that, we would have to put the solid dodecanoic acid into a beaker full of 55 deg. Celsius water.  With hot plate under the beaker. The temperature would also be taken every 30 seconds and be recorded.  Then we cleaned up with rinsing our hand with soap and water. 

-A video of demonstrating melting and freezing of a substance.
Some info on dodecanoic acid