中三化學 20點!

以下我全用Mg來做一個例子:

第1題:
a.化學特性(chemical properties):
最主要就係話一樣野,可以同乜野物質產生乜野反應
e.g. Mg + 2HCl --> MgCl2 + H2 (Mg可以同acid反應,產生salt同hydrogen gas)
2Mg + O2 --> 2MgO (Mg同空氣反應,產生MgO)
係( )裡面個d全部都係Mg的化學反應。

b.物理特性(physical properties)
同chemical properties岩岩相反,佢所謂的特性全部都唔會係一d化學反應
e.g. Mg的bp同mp都好高(注意將Mg由solid轉做liquid,gas唔係一個化學反應,裡面只涉及change of state, 無新的物質產生)
Mg有一個shiny surface
Mg唔溶係水
你會見到上面的properties都唔關化學反應事,只係一d好普通的properties
(以下就係一d physical properties的e.g.:
- apperance, bp, mp, strength, solubility等等)

第2題
a.化學變化 (chemical change)
指的係一個有新物質出來的化學,e個就係一個化學變化
e.g. Mg + 2HCl --> MgCl2 + H2 (係e個反應裡面,Mg同acid反應,變成MgCl2 同H2,有新野出來,於是我地話將Mg掉落acid到,e個就係一個化學變化)

b. 物理變化(physical change)
有新物質出來的就係化學反應,無新野出來的變化就係物理變化
e.g. 將Mg由solid加熱,變成liquid,gas,佢裡面無新物質出來,即使佢係gas,liquid,佢都係Mg

第3題
問題最主要係分辨乜野係變化同特性
從上面的例子,都可以見到變化真係只係一個變化,指的只係一個反應的轉變。記住的係:所有的化學反應都係一個化學變化,因為所有的化學反應全部都有新的物質出來。
但特性係指一個物質有d乜野的特別,例如:Mg會同空氣反應而氧化,e個就係佢的特性。
以同一個反應來說:
Mg + 2HCl --> MgCl2 + H2
變化: Mg 同acid 反應,出hydrogen gas (chemical change)
特性:Mg的特性就係,當佢掉落acid度個時,會有hydrogen gas出來 (chemical properties of Mg)

Chemical Property is the characteristic (特徵) behaviour that occurs when a substance interacts ( 交互作用) with another to become a new substance. Methane burns in air to form carbon dioxide and water,


Physical property is the characteristic or description of a substance that can be used to identify it. (e.g. state of matter at room temperature (solid, liquid, or gas), hardness, melting and boiling points, odour(氣味), solubility (溶解度) and colour)
Water freezes at zero degree C and boils at 100 degree C.


Chemical change is the alteration(變更) of a substance into one or more different substances with different properties. This involves re-arrangement(重新整理) of atoms inside a substance. The change is irreversible (不能倒逆的) most of the time.
(e.g. burning of a piece of paper, rusting(生锈) of a nail)


Physical change is a change in the size of a form of a substance, which does not change the chemical properties of the substance.
(e.g. melting of ice)


Property (性质), 是個 noun, 是東西擁有特徵, Change是變化, 是verb and noun, 要做,實行動作 (action) 纔能有變化. 例如去燃燒, 有自然做.º

2.化學變化(chemical change).作出反應后,有新物質
eg:燒一張纸. 過程中產生二氧化碳,灰等等會
二氧化碳,灰便係新物質.
物理變化(physical change)作出反應后,冇新物質
eg: freezing water
因為冰和水的結構一樣

物理變化同物理特怔的不同係過程中有冇新物質的產生

1.
物理特性(physica: properties)物質的特怔
eg:boiling point melting point,density.....
化學特性(chemical properties)作出反應的所需條件