F.3 Chem. *勁人入！

wingb

2009-09-24 3:00 am

1. Explain the difference between an 'observable change' and a 'visible change' .

2. Give an example of a reaction in which there is no visible change but there is an
observable change. Explain why.

3. Explain the difference between physical change and chemical change.

*第一二題用英文;第三題用中文 !
thZZZZZZ : )

回答 (1)

老爺子

2009-09-24 8:08 pm

✔ 最佳答案

1.
An observable change is the change which is observed by our senses including sight, smell, hearing, taste (although it is not allowed in laboratory) and touch.

A visible change is the change which is observed by our sight.

2.
Example: Heat is given off when dilute hydrochloric acid and dilute sodium hydroxide undergoes neutralization.

The heat given out cannot be detected by our sight, and thus the change is not visible. However, the heat given out can be detected by our touch, and thus the change is observable.

3.
A physical change is the change in which no new substance is formed.
物理變化是沒有新物質形成的變化。

A chemical change is the change in which one or more new substances are formed.
化學變化是有一種或以上新物質形成的變化。

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