hello,
Hi. my name is chengjiahuiamanda. and i like shitty colours and basketballs. and the piano.im a christian. My blog is a collection of my perspectives, thoughts and emotions.
God bless,
loves amanda.
Monday, September 22, 2008
yes. lest then 2 weeks till EOYS.
great. just great.
everyone's mugging and i feel out of place.
yea. and i feel like going on hiatus.
hahahha. maybe maths isnt so bad.
maybe not. goodbye.
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NOTES FOR SCIENCE
ACIDS
Acids are a group of compounds which have the following general properties:-
1. They react with metals giving a salt and hydrogen.
2. They change the colour of certain coloured substances. (indicators)
3. They react with carbonates giving carbon dioxide.
4. They react with bases giving a salt and water.
5. Sour taste (the word "acid" means sour).
Notes
All acids contain hydrogen.
Acids may be concentrated (little or no water added)
or dilute (much water added)
Some common acids are:- sulphuric acid H2SO4
hydrochloric acid HCl
nitric acid HNO3
ethanoic (acetic) acid CH3COOH
Oxides of non-metals (e.g. sulphur, nitrogen, carbon) usually produce acids when dissolved in water.
ALKALIS
Most bases are insoluble. A base which is soluble is called an alkali. The only common alkalis are:- sodium hydroxide NaOH
potassium hydroxide KOH
calcium hydroxide Ca(OH)2
Ammonium hydroxide, NH4OH is usually grouped with the alkalis.
Properties of Alkalis
1. They change the colour of indicators.
2. They precipitate the hydroxides of many metals from solutions of salts of those metals.
Example:- when sodium hydroxide solution is added to copper sulphate solution, a precipitate
of copper hydroxide is obtained.
Equation: CuSO4 + 2NaOH ® Cu(OH)2 + Na2SO4
3. They liberate ammonia gas when heated with ammonium salts.
4. Like all bases, they react with acids giving a salt and water only.
Example:- sodium hydroxide reacts with hydrochloric acid giving sodium chloride and water.
Equation: NaOH + HCl ® NaCl + H2O