March 2, 2014

10th Chemistry New Syllabus - Chemical Reactions and Equations

Chapter 1 - Chemical Reactions and Equations

In lower class you have studied about various changes like temporary changes, permanent changes, natural changes and man made changes etc. and categorized them as physical changes and chemical changes. In this chapter we discuss about chemical changes, reactions in these changes and expressing the reactions in symbolic form.

Consider the following events and think about changes and reactions that are taking place during the occurrence of events.

- coal is burnt.
- food gets digested in our body.
- iron nail is exposed to humid atmosphere for a longtime.
- we respire.
- milk is converted into curd.
- water is added to quicklime.
- crackers are burnt.

What changes do you notice?
Are they physical changes or chemical changes?
Are they temporary changes or permanent changes?

In all the above events, the nature of original substance is changed. Whenever new substances are formed with properties completely unlike those of the original substances, we say a chemical change has taken place.

How do we know a chemical reaction has taken place?
Let us perform some activities to know this.

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