Lesson 4

Lesson 4:
Acids and Bases

There are 3 main 'formulae' to this topic.
1) Acid + metal = salt + hydrogen
2) Acid + carbonate = salt + carbon dioxide+ water
3) Acid + alkali = salt + water
Went to science lab to observe the reactions of these formulae. Effervescence observed for formulae 1 and 2. White precipitate formed. :)

Here are some of the common acids and alkalis found in our daily lives.
Weaver ant: Formic Acid
Coca Cola: Phosphoric Acid
Wasp stings: Alkaline
Antacids: Magnesium Hydroxide
Bee sting: Acidic

Base: a base is an alkali soluble in water or insoluble in water.

Acids: an acid is a substance which produces hydrogen ions as the only positive ions when it is dissolved in water.
Strong acids include hydrochloric acid, nitric acid and sulfuric acid. Weak acids include ethanoic acid, malic acid, tartaric acid and citric acid.
The strength of an acid depends on its degree of ionisation in water to form hydrogen ions.

Chemical Equations:

Since chemical equations is not a big topic, I shall squeeze it in here. :)
Word equations:
Hydrogen sulfide + magnesium = magnesium sulfite + hydrogen
(see formula 1 above)
Hydrochloric acid + calcium carbonate = Calcium chloride + carbon dioxide + water
(see formula 2 above)

We also learnt how to balance chemical equations which requires a lot of memorizing.

example: HCL + CaCO3 = CaCL + CO2 + H2O
becomes: 2HCL + CaCO3 = CaCl2 +CO2 + H2O

It may seem difficult at first but remember, practice makes perfect! :D


My Reflections: These topics snatched my attention for the whole of term 2. Having gone through the pains of losing marks due to not memorizing stuff in term 1, I set my mind into the task of memorizing another whole lot of stuff for term 2. Chemical equations are not as difficult as they seem as it is mostly a matter of addition and subtraction using the elements. The challenge comes from memorizing the elements and their individual charges as each element is represented differently and has a different charge. The charge will affect the whole equation afterwards and thus, not memorizing them will prove to be a costly mistake. The topic on Acids and Bases was not too difficult as there were only 3 formulae   to memorize. Needless to say, I was not very good at it at first and kept confusing the formulae around until i finally learnt them. :D