Chemical Reactions and Equations

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CHAPTER ONE Chemical Reactions and Equations

Consider the following situations of daily life and think what happens when milk is left at room temperature during summers.

an iron tawa/pan/nail is left exposed to humid atmosphere.

grapes get fermented.

food is cooked.

food gets digested in our body.

we respire.

In all the above situations, the nature and the identity of the initial substance have somewhat changed. We have already learnt about physical and chemical changes of matter in our previous classes. Whenever a chemical change occurs, we can say that a chemical reaction has taken place.

You may perhaps be wondering as to what is actually meant by a chemical reaction. How do we come to know that a chemical reaction has taken place? Let us perform some activities to find the answer to these questions.

Activity ONE point ONE

Clean a magnesium ribbon about three to four centimeters long by rubbing it with sandpaper.

Hold it with a pair of tongs. Burn it using a spirit lamp or burner and collect the ash so formed in a watch-glass as shown in Figure ONE point ONE. Burn the magnesium ribbon keeping it away as far as possible from your eyes.

What do you observe?

Activity ONE point TWO

Activity ONE point THREE

ONE point ONE Chemical Equations

ONE point ONE point ONE Writing a Chemical Equation

ONE point ONE point TWO Balanced Chemical Equations

One point two TYPES OF CHEMICAL REACTIONS

One point two point one Combination Reaction

Do You Know?

One point two point two Decomposition Reaction

Activity one point six

Activity one point seven

Activity one point eight

Carry out the following Activity

One point two point three Displacement Reaction

One point two point four Double Displacement Reaction

One point two point five Oxidation and Reduction

One point three HAVE YOU OBSERVED THE EFFECTS OF OXIDATION REACTIONS IN EVERYDAY LIFE?

One point three point two Rancidity Have you ever tasted or smelt the fat/oil containing food materials left for a long time?

What you have learnt

EXERCISES

Four. What is a balanced chemical equation? Why should chemical equations be balanced?

Six. Balance the following chemical equations.

Seven. Write the balanced chemical equations for the following reactions.

Eight. Write the balanced chemical equation for the following and identify the type of reaction in each case.

Nine. What does one mean by exothermic and endothermic reactions? Give examples.

Eleven. Why are decomposition reactions called the opposite of combination reactions? Write equations for these reactions.

Thirteen. What is the difference between displacement and double displacement reactions? Write equations for these reactions.

Fifteen. What do you mean by a precipitation reaction? Explain by giving examples.

Eighteen. Why do we apply paint on iron articles?

Twenty. Explain the following terms with one example each.

Group Activity

Overview

This chapter provides an overview of chemical reactions, including definitions, representations through word and chemical equations, and methods for balancing these equations. It aims to enhance students' understanding of chemical changes through practical activities and examples.

Key Points

1Chemical reactions involve changes in the identity and properties of substances
2Reactants are transformed into products through chemical reactions
3Activities demonstrate practical applications of chemical reactions
4Balanced chemical equations follow the law of conservation of mass
5Physical states of reactants and products can be indicated in chemical equations

Details

Category: Education

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