Chemical Reactions

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Decomposition of Copper Carbonate

Simple substitutions reactions.

They are chemical reactions in which one of the elements substitutes another element in a solution of one of its compounds. 

A + BC                                     AC + B

As element (A) is more active than element (B)

A metal substitutes the hydrogen of water or acid

- Active metals substitute hydrogen of water and the produce metal hydroxide and hydrogen gas evolves. - Active metals substitute hydrogen of an acid and produce salt and hydrogen gas evolves.

Types of chemical reactions

First. Thermal decomposition reactions.

Second. Substitution reactions.

Third. Oxidation and reduction reactions

Lesson.2 Thermal decomposition reactions.

Thermal decomposition reactions

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.

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

Watercolor texture 1

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Decomposition of Cu(OH)2

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

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.

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

To discover the substitution of a metal to hydrogen of water:

Put a small piece of sodium by using tongs in a glass of water. Sodium burns with a pop sound (explosion)

Sodium reacts with water ( strongly) giving sodium hydroxide and hydrogen gas evolves which burns with a Pop sound. 

<a href="https://www.youtube.com/watch?v=ODf_sPexS2Q">https://www.youtube.com/watch?v=ODf_sPexS2Q</a>

Be careful when performing this reaction as this will lead to explosion and also burning. So you must use a small piece of sodium. 

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

1- The thermal decomposition of mercuric oxide ( HgO )

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 ).

Lesson.3 Substitution reactions

Substitution reactions.

They are the reactions which depends on the activity of metals where the element which is more active substitutes the less active one in another compound.

The activity of metals can be determined by using the chemical activity series

Chemical activity series

It is the arrangement of metals in descending order according to the degree of their chemical activity.

All elements above hydrogen in the series replace hydrogen in acids solutions, whereas the elements that follow hydrogen don't replace hydrogen in acids except on the certain conditions.

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

2- The thermal decomposition of copper carbonate CuCO3

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).

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

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.

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.

Decomposition Mercuric (II) Oxide into mercury and Oxygen

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