Chemical reaction and equation
Have you ever observed what happens when –
i)Milk is left as such at room temperature during summers
ii) A nail ,pan,or your kitchen iron tawa is exposed to humid atmosphere in rainy
season.
You will observe that in all situations, the nature and also the identity of the substance
changes and we say that a chemical reaction has occurred.
Now the question is how do we com e to know that a reaction has occurred.
A reaction is said to have taken place if during the process there is –
i) Change in colour
ii) Change of state
iii) Evolution of gas
iv) Change of temperature
On the basis of above conclusions, if we observe around us, we can say that a large
variety of chemical reactions are taking place around us.
Chemical reaction-
Chemical reaction is a process which transforms one or more substances into new
substances.
During chemical reactions, new substances with new properties are formed.
The substance which take part in a chemical reaction are called reactants.
The substances which are formed as a result of chemical reaction are called
products.
, e.g. sodium hydroxide reacts with hydrochloric acid to produce sodium chloride
and water.
NaOH + HCl → NaCl + H₂O
ENERGY OF CHEMICAL REACTIONS
Chemical reactions always involve a change in energy. Energy is neither created or
destroyed. Energy is absorbed or released in chemical reactions. Chemical reactions
can be described as endothermic or exothermic reactions.
Endothermic Reactions
Chemical reactions in which energy is absorbed are endothermic. Energy is
required for the reaction to occur. The energy absorbed is often heat energy or
electrical energy. Adding electrical energy to metal oxides can separate them into
the pure metal and oxygen. Adding electrical energy to sodium chloride can cause
the table salt to break into its original sodium and chlorine parts.
Exothermic Reactions
Chemical reactions in which energy is released are exothermic. The energy that is
released was originally stored in the chemical bonds of the reactants. Often the heat
given off causes the product(s) to feel hot. Any reaction that involves combustion.
(burning) is an exothermic chemical reaction
Chemical Equations-
Chemical equation is short hand representation of of a chemical reaction, in terms
of symbols and formulae of reactant and the products.
Consider the reaction between silver nitrate and sodium chloride to produce silver
chloride and sodium nitrate.
Silver nitrate + Sodium chloride→ Silver chloride + Sodium nitrate
Now putting the formulae of all the substances in above word equation, we get the
chemical equation:
Have you ever observed what happens when –
i)Milk is left as such at room temperature during summers
ii) A nail ,pan,or your kitchen iron tawa is exposed to humid atmosphere in rainy
season.
You will observe that in all situations, the nature and also the identity of the substance
changes and we say that a chemical reaction has occurred.
Now the question is how do we com e to know that a reaction has occurred.
A reaction is said to have taken place if during the process there is –
i) Change in colour
ii) Change of state
iii) Evolution of gas
iv) Change of temperature
On the basis of above conclusions, if we observe around us, we can say that a large
variety of chemical reactions are taking place around us.
Chemical reaction-
Chemical reaction is a process which transforms one or more substances into new
substances.
During chemical reactions, new substances with new properties are formed.
The substance which take part in a chemical reaction are called reactants.
The substances which are formed as a result of chemical reaction are called
products.
, e.g. sodium hydroxide reacts with hydrochloric acid to produce sodium chloride
and water.
NaOH + HCl → NaCl + H₂O
ENERGY OF CHEMICAL REACTIONS
Chemical reactions always involve a change in energy. Energy is neither created or
destroyed. Energy is absorbed or released in chemical reactions. Chemical reactions
can be described as endothermic or exothermic reactions.
Endothermic Reactions
Chemical reactions in which energy is absorbed are endothermic. Energy is
required for the reaction to occur. The energy absorbed is often heat energy or
electrical energy. Adding electrical energy to metal oxides can separate them into
the pure metal and oxygen. Adding electrical energy to sodium chloride can cause
the table salt to break into its original sodium and chlorine parts.
Exothermic Reactions
Chemical reactions in which energy is released are exothermic. The energy that is
released was originally stored in the chemical bonds of the reactants. Often the heat
given off causes the product(s) to feel hot. Any reaction that involves combustion.
(burning) is an exothermic chemical reaction
Chemical Equations-
Chemical equation is short hand representation of of a chemical reaction, in terms
of symbols and formulae of reactant and the products.
Consider the reaction between silver nitrate and sodium chloride to produce silver
chloride and sodium nitrate.
Silver nitrate + Sodium chloride→ Silver chloride + Sodium nitrate
Now putting the formulae of all the substances in above word equation, we get the
chemical equation:
