Summary of Textbook (p25-34, 36-39)

Hello

Today we are going to explain CH.2 of the Chemistry textbook.

From the previous posts, we explained to you that matter is everything around us.

However to understand matter fully, we must look at it on a macroscopic level.

This is like look at the sand on a beach.

If we see this sand from far away, all we see is a blob of light brown.

However, if we look closely, we can see the individual grains of sand.

In our world, matter can be in a form of a mixture, which is formed with 2 or more kinds of matter that have separate identities.

Classifying matter into either a pure form or a mixture is a big step in unders
tanding matter.

You can make a mixture by simply adding stuff to your water maybe Kool-Aid or sweetners.
Sometimes, you can find a mixture that does not scatter light and looks uniform throughout. These mixtures are called solutions.

Mixtures can be separated by using different procedures(eg. distillation).

There are few characteristics that you should know about Pure Substances:
actually you need to know this fact: the melting point and the freezing point of a pure substance is the same!!

(Info of chemical and physical changes: refer to "Changes in Matter" article)

There are few rules that you need to know (in general)

Law of Definite Composition: The compounds will have a definite composition.

Law of Multiple Proportions: The fact that two or more compounds with different proportions of the same elements.

(For summary of p36-39) refer to "All about Matter!!" article.

Thanks for tuning in.

Written by JK (Oct4,2010)

PS been edited a few times

More Details in Separation (Hehehe...)

Helloo!! We are back.

We are going to tell you more about different separation techniques.

Hand Separation:

• Used usually for mechanical mixture or heterogeneous mixtures
• separation by a hand, magnet or a sieve
• Evaporation which is solid dissolved in liquid solution or boil away the liquid and solid remains

Filtration:

• deals with solids(not dissolved) and liquids
• passing a mixture that contains solid particles through a porous filter
• the liquid pass through the filter and residue is left on the filter
• separation by using filter paper

Crystallization:

• solids in liquids
• Precipitation: conversion of a solute to solid form by chemical or physical change
• after, solids are separated by filteration or floatation
• saturated solution of a desired solid evaporate or cool - solid come out as crystals

Gravitiy Separation:

• solids based on gravity
• centrifuge whirls the test tube around at high speed forcing the denser materials to the bottom
• Works best for small volumes

Solvent Extraction:

• a component moves into a solvent shaken with the mixture
• works best with solvents that dissolve only one component
• For mechanical mixtures: use liquid to dissolve one solid but not the other so that the desired solid is left behind or dissolved
• Solution: solvent is insoluble with solvent already present

Distillation:

• Heating a mixture creates vapour
• collecting and condensing vollatillized components
• liquid with lowest boiling point boils first
• vapour ascents to distillation flask and enters condenser
• gas cools and condenses > back to liquid and distillates as a purified liquid

Chromatography:

•  Flow mixture over a material and different components goes in different speeds and stops
• mobile phase sweeps the sample over a stationary phase
• can separate complex mixtures
• very small sample sizes; analysis is highly accurate and precise
• separated components can be collected individually

Paper Chromatography:

•  Stationary Phase: liquid soaked into sheet of paper
• Mobile Phase: liquid solvent some components spend more time in the stationary phase than others after drying; spots appear on the paper

Thin layer Chromatography (TLC):

• Stationary Phase: thin layer of absorbent (Al203 or SiO3) coating a sheet of plastic or glass
• some components bond to the absorbent strongly; others more weakly
• appear as spots

Written by JK (Oct 18, 2010)

Separation Techniques

Hello everyone, we are back again.

Today we will talk to you about basics of separating different components and properties.

Separations are all about mixtures and distinguishing the different components and properties in them.

 Before we learn the different techniques to separate mixtures, we need know a few things. :D

• Components in a mixture do not lose their identities

• Components have different properties

• More similar the properties are, more difficult it is to separate.

Also one more thing, when you want to separate a mixture, you need to have a strategy which is to devise a plan with the different techniques to discriminate between components with different properties.

Now onto the different types of separation:

Filtration: This method separates the components by particle size.

Filtration

Floatation: This method separates the components by density.

Crystallization: This method separates the components by solubility(ability to dissolve).

                                 

 Extraction: This method separates the components by solubility.

                                  

Distillation: This method separates by boiling point.

                               

Chromatography: This method separate components by affinity for a stationary phrase.

                                         

Now you have learned the different types of separation.

Tune in soon to learn more about separation in detail.

Written by JK(Oct, 18/2010)

How to Name Complex Acids

Hello we are back with more acids!! (AHHH!! It's burning my face!!)

Here are the rules:

1. any polyatomic atoms(that are negatively charged) that end with --ate replace with --ic
    any polyatomic atoms(that are negatively charged) that end with --ite replace with --ous

2. Put "acid" at the end

Examples:

HCH3C00 - acetic acid (CH3C00 is acetate which you need to replace with --ic)

HClO3      - chloric acid (ClO3 is chlorate which you need to replace with --ic)

HClO2      - chlorous acid (ClO2 is chlorite which you need to replace with --ous)

H2SO3      - sulphurous acid (SO3 is sulphite which you need to replace with --ous)

So this is basically how you name acids!!! :D

Thanks for tuning in!! Bye!


Written by JK (Oct 14,2010)

How to Name Acids

Acids are formed when a compound compsed of hydorogen ions and negatively charged ions become an aqueous or dissolved in water.

*Note: all numbers underlined are subscripts.

In water, these ions separate when dissoved. Also hydrogen ions join with H20(water) to form H30 (hydroniums)



Eg. H+ Cl - => HCl

       HCl (g) +H20 => H30 (aq)  + Cl (aq)

Guidelines in Naming Acids:

For columns 16 and 17, use simple acid formulas.

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

* ________ide  → hydro___ic acid

Eg.

1. HF(aq)  -  hydrofluoric acid

2. HCl(aq) -  hydrochloric acid

3. HBr(aq) - hydrobromic acid

4. HI (aq)  -  hydroiodic acid

5. H20 (aq)  - water  :D

6. H2S (aq) - hydrosulphic acid

7. H2Se (aq) - hydroselenic acid

Written by : JK (Oct 14, 2010)

Answers from the changes in matter questions

Here are the answers:

a) physical change because fog is water vapour that is condensed into droplets of moisture

b)chemical change because new substances are formed: smoke and cancer cells-causing chemicals)

c)chemical change because the growth involves chemicals being produces and used up

d)chemical change because rust is a new substance formed by combination of iron, air and water)

e)physical change because no reaction has occurred to make new substances

f) physical change because we are only separating substances, not producing new ones

If you got perfect, you are ready to go but if you got less than 4 you need to study... :(

Written by JK

Changes in Matter

There are 2 main changes in Matter : Physical and Chemical

In a Physical Change:

no new substance is formed

the chemical composition does not change

it is reversible (you can drink water(liquid) if you melt ice :)

Eg. boiling point, melting point

In a Chemical change:

it is irreversible (you can't undo a salad dressing)

new substances are produced

Eg. burning, cooking

So these are the basic changes in matter

Here are some questions that you can answer.

Classify each of the following as either chemical or a physical change

a) formation of a fog
b)burning a cigarette
c)sprouting of a seed
d)rusting of iron
e) mixing yellow and blue paint to make green paint
f) separating an alcohol- water mixture into water and alcohol

The answers will be up shortly!

Written by JK