Chemistry 問題

1.
burning paper
paper is CxHxOx
CxHyOz + O2 = CO2 or
CxHyOz + O2 = CO2 + H2O
二氧化碳就係new substance.而灰,就係d未完全燒哂ge碳or paper.

係一個完全ge combuction(burning),係唔會有灰ge,灰只係因為paper未完全同氧做反應而剩低ge paper.

e個應該唔算係new subtance,你見到ge灰,有時仲可以係上面睇到d字,佢變左灰黑色,係因

為其他碳粒stick左上去,佢變左形,係因為高溫,係e個過程中,佢ge chemical composition冇改變到,所以灰都係paper,唔算new subtance.

2.
二氧化碳,係new subtance, 因為佢ge化學成份同paper以經唔一樣,二氧化碳係CO2,paper is CxHyOz.
灰,多數唔係,佢只係高溫下變左形ge paper.

3.
e個只係佢ge physical　properties, pH paper係唔同ｇｅ　ｐｈ係有唔同ｇｅ顏色,e個係

佢ge物理性質,過程中冇化學反應.

其實ph paper係由幾種唔同ge pH indicator 混合,包括甲基橙,酚酞等

4.
因為當你測試水個pH ge時間,根本就唔會有new subtance form,而且水ge 化學成份亦唔會改變,所以e個係physical preperty.

總之記住, 一個property/reaction, 只要唔涉及本身化學成份有改變(e.g. C變做CO2),or

new subtance form(C + O = CO2), 佢就係physical properties/ reaction.

舉例,碳其中兩個特性, 佢導電(石墨,其中一種碳的同素異形體,會導電,鉛筆的筆芯就係石墨), 同埋,佢會同氧做反應,形成二氧化碳.

的一個係physical property, 因為佢導電ge過程冇new substance formed, 而佢自己ge化學成份都冇改變, 第二個就係chemical property, 因為同氧做反應ge過程中有 new subtance formed, 佢自己都變左做CO2

講講 DENFINITION 先

chemical reaction is a reaction that a new substance formed during the reaction

physical reaction is a reaction that no new substance formed .


BURNING PAPER

paper 係 CxHyOz 燒 即係 + nO2 變做 C + CO2 + H2O (未 bal)

灰就係carbon 即係 C


TEST pH VALUE 比人TEST 既 SOLUTION 冇 chemical reaction

但係 INDICATOR 就有啦'' 唔係點會變色

不過 用 pH METER 就唔清楚


physical property 係講佢本既既變化
FOR EXAMPLE , 水 變做ICQ 都係 PHYSICAL
但係CHEMICAL 就可能係電解 '' 有 H2 + O2 (電解水唔會係PURE WATER)

H2O 係 pH 7 因為
concentraion of hydrogen ions = conc. of hydroxide ions

1. 是. 紙同碳擺明唔同.

2. 算. 紙同碳擺明唔同.

3. 佢係固體.

4. 化學特性係指物質同其他物質化學反應
pH值同化學無關