點先知出咩化學反應?

1)你要寫得出條Chemical Equation

2)有冇bubble?

3)有bubble話，bubble咩色( colourless or coloured?)

4)有bubble話，bubble有多少?(少嘅e.g.CO2可以就咁寫 "colourless gas
bubble is given off"，多嘅就要寫"effervescence occurs".通常reaction of
hydrocarbonate, carbonate, 出 sulphur dioxide 先有 effervescence )

5)有咩嘢溶咗? e.g. zinc dissolves in dil. hydrochloric acid

6)有冇ppt(precipitate)?

7)有ppt的話，ppt 咩色?

8)有ppt的話，如果可以寫埋ppt的特徵會更好，如curdy solid, gelatinous solid.
當然唔識唔好寫呢個!

9)solution有冇轉色?

10)有冇氣味?
見到SO2 就寫 "bad egg smell occurs"
見到NH3 就寫 "pungent smell occurs"

11)reaction係熱定凍?(FORM4 應該唔駛寫住)
exothemic or endothemic?

12)以上有啲冇嘅唔駛寫。咩都冇寫 "no observable change"
#千其唔好寫"no reaction"

E.g.
Zinc is reacted with dil. HCl
Observation: Zinc dissolves in the solution and colourless gas is given off

Copper is reacted with silver nitrate solution
Observation: Copper dissolves to change the solution from colourless to blue.
Silvery solid is formed in the solution

Iron is reacted with copper sulphate solution
Observation: Iron dissolves to change the solution from blue to (pale) green.
Reddish brown solid is formed in the solution

#見到metal FORM咗唔好寫佢個名，係寫佢嘅顏色。

Copper is added to dil.HCl
Observation: There is no observable change

*=難嘅example

*Iron(ii) ion is reacted with excess OH- ion
Observation: Dirty green gelatinous ppt is formed.

**Zinc ion is reacted with excess NaOH
Observation: White gelatinous ppt is formed at first, then it dissolves to
give a colourless solution

不是死背, 而是有方法的

簡單來說, 化學方程式可以是千變萬化, 但以HKDSE的SYL來說, 其實只考很少很少的地方.

我的學習方法很簡單, 就是將每課反應種類變做數字, 如:

酸

酸的反應 = 3

1. 酸+金屬
2. 酸+ CO3 2- / HCO3 -
3. 酸 + 鹽基

注意: 如考呢一課, 會考的只有這三個反應(後期會再多幾個反應),你只要記住他們的反應物/生成物即可, 大大減少背誦數量, 和令學習目標更清晰.

其實睇得到就發覺好有規律，好多都係就咁置換，有D特別D就要死記一下，如果識氧化還原就可以睇價態估生成物出尼...我係咁做的.