{SOMEWHERE OVER THE RAINBOW.}

Saturday, October 4, 2008

title:{Chemistry...}

Chemistry...

Yup, Bio & SS is over! haiz, got to write alot on tt dae... Sianz... Yups, nxt up is Chem & Chinese oral on Mon... I'm quite okay wif chinese oral, coz I always speak mandarin at home, but for chem its a disaster 4 me!! Ugh, most of e stuff dun understand, somemore Mrs Ooi always tok soooo fast lo, somemore e Qns are always very complicated lo, haiz... So yup, studying here todae! Anyways, I found out tt the words on my blog is rather small, so I'm making 'em larger!

Chemistry(Chp1~14 & 16)

Measurements in Chemistry
Measuring cylinder - 1cm³ {Vol. of liquid}
Pipette[20.0/25.0cm³] - 0.1cm³ {Vol. of liquid}
Burette[0-50cm³] - 0.1cm³ {Vol. of liquid}
Beaker - 10cm³(approx.) {Vol. of liquid}
Syringe - 0.1cm³/1cm³(depending on size) {Vol. of gas/liquid}

Collection of gases
1. Displacement of water [not suitable for gases tt are very soluble in water] (eg. NH3, HCl, SO2, Cl2, H2S)
2. Displacement of air
-By downward delivery[Denser than air] (eg. Cl2, CO2, Br2)
-By upward delivery[Less dense than air] (eg. H2, He, NH3)

Drying of gas
Drying agents - fused calcium chloride(neutral), calcium oxide(base, solid, not for acidic gases), concentrated sulphuric acid

Separation Techniques
2Solids
1. Solution, filtration, evaporation/crystallisation [one is soluble in solution] (eg. salt & sand)
2. Use a magnet [one is magnetic]
3. Sublimation [one sublimes] (eg. I2 & NaCl, NH4Cl & NaCl)
2Liquids
1. Seperating funnel [immiscible liquids] (eg. oil & water)
2. Fractional distillation [miscible liquids] (eg. crude oil/petroleum)
Solid frm liquid
1. Filtration [small particles]
2. Decanting [large particles]
3. Evaporation/Crystallisation
Liquid frm Solid
1. Simple distillation (eg. sea water)
Others
1. Paper Chromatography
-Rf=distance travelled by substance ÷ distance travelled by solvent

Examples of Mixture
Air
78% of N2, 20% of O2, 0.03% of CO2, 19% of [Ar, He, water vapour & others]
Crude oil
methane, petroleum gas, napthelene, petrol, kerosene, diesel & bitumen

Bonding
Ionic[metals & non-metals] - giving off electrons
-Giant Lattice Structure(strong), eg.NaCl
-High b.p., m.p.
Covalent[non-metals] - sharing of electrons
-Giant molecular structure
-Simple molecular structure
-Low b.p., m.p.
metallic[metals] - electrons delocalised, surrounding the positive ions
-free & mobile electrons
-pure metals
-soft & malleable
Metal elements->less than 4 electrons in the valence shell
Non-metal elements->more than 4 electrons in the valence shell

Acids, bases & salts
Acids + metal --> Salt + H2
Acids + base --> Salt + H2O
Acids + carbonate --> Salt + H2O + CO2
An acid is a compound which produces H+ in water.
Bases are oxides and hydroxides[insoluble bases] of metals, including aqueous ammonia.
Alkalis are soluble bases.
Acids neutralise a Alkali or a base to form salt.
*All [ACIDS, ALKALIS, SALTS TT ARE SOLUBLE IN WATER] are aqueous!*
*All gases are gaseous!*
*Water & concentrated Sulphuric acid are liquid!*
*Insoluble bases & metals are solid!*
Some acids:
-Sulphuric acid, H2SO4
-Sulphurous acid, H2SO3
-Hydrochloric acid, HCl
-Nitrate acid, HNO3
-Carbonate acid, H2CO3
-Ethanoic acid, CH3COOH
-Phosphoric acid, H3PO4
Writing ionic equations
1. Write a balanced equation with state symbols.
2. For aqueous solution, ions are dissociated.
3. Cross out spectator ions. Rewrite with state symbols.
Oxides
Non-metals
-Acidic->becomes an acid when placed in water, not soluble in alkali (eg. SO2, SO3, CO2, NO2, SiO2)
-Neutral->insoluble in water, acid & alkali (eg. H2O, CO, N2O)
Metals(Bases)
-Basic->forms salt & water when placed in acid, insoluble in alkali (eg. MgO, Na2O, CaO, CuO, Cu2O, FeO, Fe2O3)
-Amphoteric->metallic oxides tt react with both acids and alkali to form salt & water (eg. Al2O3, ZnO, PbO)
Acids
-Sour
-pH-> concentration of H+ ions.
-strong->acid ionised completely
-concentrated->have more H+ ions
-strong, concentrated acid->very corrosive
Alkali
-Bitter
-Soapy/slippery
-eg. KOH, NaOH,Ca(OH)2[lime water]

All rite, got to go, will continue 2moro... So gd nitez! Sayonara...

A lollipop a day, keeps my sorrows away...

2:19 PM;