Tuesday, October 14, 2008

POLYMERS- NOTES




<<strong>A polymer is a large molecules composed of repeating structural units (monomers) connected by covalent chemical bonds



It’s the breaking down of double bond carbon atoms , and the the electrons in it are used to join to neighboring molecules .

In its case polymerization take place ,where lots of little molecules(monomers) join up to make one big molecule (polymer)



In the case of ethene lots of ethene molecules join together to make poly(ethene)


When propene polymerized you get polypropene



Polymerising chloroethene gives you poly(chloroethene).

2- condensation polymer

Here the polimerisation method is totally different . if one monomer contains an – OH group and the other an –H , then they add by forming a molecule of water . when they polymerise , the water molecule is split out between them .
Also the same way in splitting out of HCL molecule.


*by removing water

HOOC- ___ ___ COOH + H2N- ___ ___ NH2 --
(carboxylic acid) (amino group)

HOOC ___ ___ CONH ___ ___NH2 +H2O
( amide linkage )


{another way }


COOH ___ ___COOH + NH2 ___ ___NH2---
(dicarboxylic acid) (diamine) -H2O

(___ ___CONH___ ___ )n


(amide linkage)


*by removing HCL

COCL ___ ___ COCL +NH2 ___ ___ NH2 -----
-HCL

(____ ____CONH ____ ____)n
(amide linkage)



*by removing water


HOOC ___ ___ COOH +HO- ___ ___OH ----
(carboxylic acid ) (alcohol)

HOOC- ___ ___ COO___ ___OH
( ester linkage )

{another way}
OH___ ___OH + COOH ___ ___COOH à
(diol) (dicarboxylic acid) -H2O

(___ ___COO___ ___)n
(ester linkage)

……………………………………………………………………….


*by removing HCL

COCL ___ ___COCL + OH___ ___OH ---
(acid chloride) (diol) -H2O

(___ ___COO___ ___)n
(dicarboxylic acid)


USES


polyethene

Bags, plastic milk bottles
Not very strong , flexible

poly propene

To make ropes and crates
strong

polyvinaly chloride

Drainpipes, replacement windows
Quite strong and rigid

nylon

Make toothbrush and ropes
strong
To make clothing
Very strong

periodic table - groups -notes



PERIODIC TABLE



The elements in the periodic table are arranged according ti the increasing atomic number. In the peridoic table there are eight main groups and seven periods.
The elements in the same groups have similar properties because they have the same number of electrons in their outer shell.
The group number of the elements is the same as the number of the outer electrons. 3/4 of the periodic table is filled with metals.



There are other elements called the semi metals whos hare both the properties of metals and non metals.They conduct like metals and are brittle like non-metals.


Reactions and electron arrangementsGroup 1 elements all have atoms with 1 outer electron. e.g. sodium 2,8,1All of these atoms try to lose 1 electron so all react in the same way.



They all form a positive ion and form ionic compounds. E.g. sodium Na form sodium ion Na+.Group 1 elements all react with oxygen (that is burn) to form oxides. The products like sodium oxide, are all ionic.

sodium burn

Group 0 elements all have atoms with complete outer shells e.g. helium 2, neon 2,8. None of these elements react with anything.

Name other elements in group 1 and say how they react with oxygen giving a reason. State how argon reacts with oxygen and give a reason.






Trends in group propertiesGroup 1 elements get more reactive with water as you go down the group. e.g.Lithium (gentle fizz) is less reactive than potassium (violent lilac flame).Group 7 elements get more reactive with iron as you go up the group.Iodine darkens iron when it is heated but chlorine makes iron burst into flames.


GROUP 1

They are called alkali metals because they react with water to form strong alkali. The increase in number of shells and atomic size causes increase ub the reactivity down the group because bigger the atom, the less its attractive force towards the nucleus.

Group 1 metals have one electron in the outermost shell which is why they are called group 1.


They are less dense than group 2 metals because they have only one electron in the outermost shell and they're stored under oil to prevent them from reacting iwth oxygen and water vapour form at the atnoshpere as it is dangerous.


Reaction with water


Sodium is a strong alkali, when it reacts with water :

1) It floats and melts.
2) Hydrogen gas is produced.
3) It forms sodium hydroxide.


Sodium + water ---------------> Sodium hydroxide + hydrogen
Na + H2O ---------------------> NaOH + H2
Na + HOH -------------> NaOH + H2


Potassium when reacting with water :

1) It floats.
2) It catches fire and burns with a lilac flame.
3) It forms potassium hydroxide and hydrogen.

Potassium + water --------------------> Potassium hydroxide + hydrogen
K + H2O --------------------------------> KOH + H2
K + HOH -------------------------------> KOH + H2


Lithium


Lithium forms Lithium hydroxide and hydrogen gas when reacting with water.

Li + H2O ----------------> LiOH + H2


Rubedium (Rb)


Rb + H2O -----------> Rb (OH) + H2



When rubedium reacts with water :


1) Heat is produced.
2) Explosion takes place.
3) It forms Rubedium hydroxide and hydrogen gas.

analysis - NOTES/ flame test


Testing ions by using flame test :
A flame test is used to show the presence of certain metal ions in a compound. A wire of platinum or nichrome is first dipped into a concentrated Hydrochloric acid and then held in a hot bunsen flame ,,this process should be done before testing any ion to clean the wire.
Test for some ions : (by using a flame test)
flame colour
ion
Red
Lithium / Li
Yellow-orange (strong yellow)
Sodium / Na
Orange-red (brick red)
Calcium / Ca
Pale green (apple green)
Barium / Ba
Lilac colour
Potassium / K
Blue-green
Copper / Cu









Tuesday, October 7, 2008

PURIFICATION AND USES OF COPPER



keep impure copper at anode and purecopper wire at cathode


At anode


Cu --------------Cu²+ + 2e-

At cathode


Cu²+ + 2e- ------------- Cu



* Salt solution of copper (CuSo4 ) is used as the electrolyte.

* The copper from the anode goes to the solution as C


* Cu²+ ion goes to the cathode and gets deposited.


Uses Of Copper:

1- Electrical wiring: good conductor of electricity.
2- Domestic plumbing: does not react with water.
3- Making alloys like brass (zinc & copper): harder than copper & zinc.
4- Making coins: long lasting without any corrosion
.

electrolysis of sodium chloride




Sodium hydroxide, chlorine and hydrogen are produced from natural deposits of sodium chloride (rocksalt). This is the basis of the chloralkali industry. Electrolysis of brine (salt solution) produces 1 tonne of chlorine at the same time as 1.13 tonnes of sodium hydroxide and 0.028 tonnes of hydrogen. There are many different processes used in the electrolysis of brine. An aqueous solution contains the following ions: Na+, Cl-, H+ and OH-.

at anode

2Cl- Cl2 + +2e-

At cathode:
2H+ + 2e- H2


* The remaining solution contains NaOH

electrolysis of lead bromide-notes

molten lead bromide is taken in the cell. Electricity is passed.


cations (Pb²+) are moving towards the cathode and get discharged as:


Pb Pb²+ + 2e-



The anions (Br-) are moving towards the anode and get discharged as:


2Cl- 2Cl2 + 2e-

oxidation and reduction- notes

Oxidation of ions or neutral molecules can take place at the anode, and the reduction of ions or neutral molecules at the cathode.

Oxidation and Reduction reactions takes place in the cell, so this is known as reduce reaction.

It can also be memorized as (OIL RIG) where Oxidation is losing of electrons and Reduction is gaining of electrons.


Substances that have the ability to oxidize other substances are said to be oxidative and are known as oxidizing agents, oxidants or oxidizers. Put another way, the oxidant removes electrons from another substance, and is thus reduced itself. And because it "accepts" electrons it is also called an electron acceptor.


Substances that have the ability to reduce other substances are said to be reductive and are known as reducing agents, reductants, or reducers. Put in another way, the reductant transfers electrons to another substance, and is thus oxidized itself. And because it "donates" electrons it is also called an electron donor.

electrolysis- notes

* Electrolysis is the process of splitting substances by passing electricity.



* Electrolysis involves the passage of an electric current through an ionic substance that is either molten or dissolved in a suitable solvent, resulting in chemical reactions at the electrodes.



* Electrodes are metals used for electrical contact. The positive electrode is called the anode and the negative electrode is called the cathode. To be useful for electrolysis, the electrodes need to be able to conduct electricity, and metal electrodes are generally used. Graphite electrodes and semiconductor electrodes are also used.


* An ionic compound, or compound that reacts with solvent to produce ions (such as an acid) is dissolved in an appropriate solvent, or an ionic compound is melted by heat.




* Each electrode attracts ions that are of the opposite charge. Therefore, positively charged ions (called cations) move towards the electron-emitting (negative) cathode, whereas negatively-charged ions (called anions) move towards the positive anode.


* Electrolytes are substances which can be split by passing electricity. They are usually ionic compounds.
E.g.: NaCl, PbBr, etc …


* The energy required to separate the ions, and cause them to gather at the respective electrodes, is provided by an electrical power supply. At the electrodes, electrons are absorbed or released by the ions, forming a collection of the desired element or compound.

summary non metals- notes

Non-metals



1- Non-metals have different physical and chemical properties to metals.
2- You can prepare oxygen, carbon dioxide, hydrogen and ammonia gases in the laboratory.
3- Ammonia can be oxidized to nitric acid.
4- Ammonium nitrate is both a fertilizer and an explosive.
5- Cooling air gives liquid air which can be separated.
6- Sulphur forms allotropes.

Experiment to show the % of oxygen in air- notes

procedure


1- Syringe A contains 100cm of air from the atmosphere.

2- The silica tube contains cooper tunings.

3.The syringe B is closed

4- Light the burner D and press the syringe A.

5- Copper react with oxygen from the syringe and forms black color copper oxide.

6- The remaining gas will be collected in syringe B which is 79 cm3.

7- So the oxygen present in air = 100-79 = 21cm3.

Extraction of oxygen and nitrogen from liquid air

Composition of gases in air - notes

GAS % IN ATMOSPHERE



Nitrogen 78%

Oxygen 21%

Argon 0.9%

Carbon dioxide 0.03%

preparation of hydrogen- notes



equation

Zn+ HCl ------ ZnCl2 + H2

sulphur- notes

S + O2--------SO2
S+ Fe ----------FeS (IRON SULPHIDE)



Sulphur : Three forms of sulphur
1- Rhombic sulphur
2- Monoclinic sulphur
3- Plastic sulphur

ammomium salts- notes

Ammonium salt:


Ammonia + Hydrochloric acid = Ammonium ChlorideIt is a reversible reaction.
Heating the NH4CL gives back NH3 and Hcl gases.
NH3 + HCL= NH4CL
NH3 + H2SO4 = (NH4)2 SO4
(NH4)2 is an important nitrogen containing fertilizer.
NH3 + HNO3 = NH4NO3 (Ammonium nitrate- fertilizer)

ammonia-notes/IGCSE /GCSE -CHEMISTRY

test for carbondioxide- notes


Turns lime water milky.
Calcium hydroxide + carbon dioxide ---------calcium carbonate + water.
Ca (OH) 2(aq) + CO2 (g) CaCO3(s) + H2O (l)

properties and uses of carbondioxide - notes/IGCSE/GCSE NOTES


1- Colorless gas.
2- More dense than air.
3- Solid below -78 degree.
4- Soluble in water.
H2o + Co2 --> H2CO3 (carbonic acid)
Carbonic acid is present in acid rain and carbonated drinks.
Uses of carbon dioxide
1- Fizzy drinks.
2- Fire extinguisher.
3- Dry ice.
4. PHOTO SYNTHEIS

preparation of carbondioxide- notes/IGCSE /GCSE/CHEMISTRY NOTES


Equation
CaCO3 + 2HCl = CaCl2 + H2O + CO2

formation of oxides- Notes

Mg + O2 --> Mgo (basic- All the metals forms basic oxides)

2- S + O2 --> So2 (Acidic- All the non-metals forms acidic oxides)

3- CH4 + O2 --> Co2 + H2o

Very important: Any hydrocarbon reacts with oxygen gives carbon dioxide and water.

reactions of copper- notes/ IGCSE / GCSE

When copper is heated in a flame, it turns black with a coating of copper (II) oxide.
Copper+ oxygen --> copper(II) oxide
2- This is an example of thermal decomposition. Copper (II) oxide is a base- it reacts with acids to form salts.
Base+ acid--> salt + water
Copper(II) sulphate + nitric acid--> copper nitrate + water
3- The formation of the deep blue complex ion with ammonia is used as a test for the presence of copper in solution. Other metals give green-blue solutions for example nickel or cobalt, but only copper forms this colored complex.
Here, ammonia (NH3) is added to copper(II) sulpate (CuSO4). The result is a pale blue precipitate, which is Cu(OH)2.
NH3 Add more the product is
(Cu(H20)2 (NH3)4 ) 2+ )
Compound Color
Iron(II) chloride Green
Iron(III) chloride Brown
Copper sulphate Blue
Copper carbonate Blue green
Copper oxide Black
Copper nitrate Blue
Copper chloride Green
Other reactions:
Fe + Hcl--> Fecl2
Fe+Cl2-->Fecl3
Cuo+Hno3-->Cu(No3)2+H2o
Cuo + Hcl --> Cucl2 + H2o
Cu + Hno3--> Cu(No3)2 + H2o + No2

reactions of iron-igcse /gcse notes

Iron reacts with solutions of dilute acids to form iron (II) salts.
Iron+ sulphuric acid --> iron (II) sulphate + hydrogen
Iron reacts slowly with water to form rust. This reaction is used to produce Hydrogen from rusted scrap iron.

Monday, October 6, 2008

atomic structure - work sheet

Answer the following
1. The smallest repeating unit of an element is called-----------------
2. Central of the atom is called---------------------
3. Name the three particles in side the atom
4. Name the negative particle in side the atom ---------------------
5. Name the positive particle inside the atom --------------------------
6. Name the path of the electron around the nucleus------------------------
7. The number of --------------------------and------------------------particles are same in
inside the atom
Try to answer the following
1.Why the atom is neutral?
2.Define mass number.
3. Define atomic number
4. Define isotopes
5.why isotopes have similar properties
6.which one of the following are isotopes
35 37 37 35
Cl , Cl , Cl , Cl
17 16 17 16
7.Draw the electron arrangement in
Magnesium, calcium , sodium, lithium, sulphur
8.Relative atomic mass of an elementUse relative mass of isotopes and their relative abundance. E.g. Chlorine has two isotopes with mass numbers 35 and 37. 35 37 75% is Cl and 25% is Cl 17 17 Let there be 100 atoms Total mass of 100 atoms = (75 * 35) + (25 * 37) = 3550 Average mass of an atom (relative atomic mass of chlorine) = Total mass /Number of atoms =3550/100 so relative atomic mass of chlorine = 35.5
Task
1. Bromine exists as two isotopes with mass numbers 81 and 79. If there is 50% of each isotope in a sample what is the relative atomic mass of bromine?
2. Calculate the relative atomic mass of the following:
(a) gallium 60% Ga 69 and 40% Ga 71
(b) neon 90% Ne 20 and 10% Ne 22
(c) silver 50% Ag 107 and 50% Ag 109
(d) boron 20% B 10 and 80% B 11

chemistry notes / igcse-gcse- Olevel

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