Chemical Reactions

Contents

Preface
Lesson.1 Chemical Reactions.
Lesson.2 Thermal decomposition reactions.
Lesson.3 Substitution reactions

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Preface

Thanks to God who helped me to introduce one famous book in science.
I introduce this book to my colleagues. I also introduced it to my pupils to help them study science
In fact this book is the outcome of more than 10 years experience in the field of teaching science.
I will be greatful if you send me your recommendations and your comments.

Marwa Mahmoud Abdullah

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Lesson.1 Chemical Reactions

Chemical reaction

It is the breaking up of bonds in molecules of the reactants and formation of new bonds in the molecules of products from the reaction.

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Chemical reactions play an important role in our daily life as in the following examples :

Burning of car fuel in the car engine generates power which makes car move.

Plants make their food through photosynthesis process which depends mainly on the reaction of carbon dioxide with water.

Medicine, fertilizers and artificial fibers and examples of outcomes of some chemical reactions.

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Types of chemical reactions

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First. Thermal decomposition reactions.

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Second. Substitution reactions.

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Third. Oxidation and reduction reactions

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Lesson.2 Thermal decomposition reactions.

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Thermal decomposition reactions

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They are the reactions which involve the breaking up of the compounds by the effect of heat into its simple elements or simpler compounds than the original ones.

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- Decomposition reaction can be represented as shown in the following figure.

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heat

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A

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B

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A

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+

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B

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We will study some activities to discover the thermal decomposition reactions:

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Activity

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1- The thermal decomposition of mercuric oxide ( HgO )

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Procedure:
1- Put a little amount of red mercuric oxide in a clean test tube.
2- Heat the content of the test tube by using a flame.
3- Approach a lighted stick of match close to the opening of a tube.

Observation:
- A silvery precipitate is formed at the bottom of the tube.
- The burning match glows more.

Explanation:
Red mercuric oxide decomposes by heat into mercury ( silvery precipitate at the bottom of the tube ) and oxygen ( which increases the flame of match ).

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Activity

2- The thermal decomposition of copper carbonate CuCO3

Procedures:

1- put a little amount of green copper carbonate in a clean test tube.
2- Heat the content of the test tube by using a flame.
3- Pass the produced gas into a clear limewater.

- A black substance is formed.
- The limewater becomes turbid.

Green copper carbonate decomposes by heat into copper oxide( black colour) and carbon dioxide( which turbids limewater).

Observation:

Explanation:

Conclusion.

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Some metal carbonate such as CuCO3 Undergo thermal decomposition into metal oxide and carbon dioxide.

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Activity

3- The thermal decomposition of copper hydroxide Cu(OH)2

Procedures:

1- put a little amount of blue copper hydroxide in a clean test tube.
2- Heat the content of the test tube by using a flame.

- A black substance is formed.

Blue copper hydroxide decomposes by heat into copper oxide( black colour) and water vapour.

Observation:

Explanation:

Conclusion.

Some metal hydroxide such as Cu(OH)2 Undergo thermal decomposition into metal oxide and water vapour.

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