notes of chapter 1 class 10 chemistry
Answers
Physical Change: Change in physical properties.
� Melting
� Boiling
� Condensation
� [Note- No change occurs in the identity of the substance].
? Chemical Change:
� Atoms in the reactants are rearranged to form one or more different substances.
� Old bonds are broken, new bonds are formed.
� Reactants lose their properties to form product of different properties.
4 Fe(s) + 3O2 ?2Fe2O3 (rust). Iron Oxygen Ferric oxide
? Chemical equation:
The symbolic representation of a chemical reaction is called a
chemical equation.
Features of a chemical equation:
� The reactants are written on the left hand side with a plus sign between them.
� The products are written on the right hand side with a plus sign between them.
� An arrow separates the reactants from the products. The arrow head points towards the products and indicates the direction of the reaction.
Skeletal chemical equation: A chemical equation which simply represents the symbols and formulas of reactants and products taking part in the reaction is known as skeletal chemical equation for a reaction.
For example: For the burning of Magnesium in the air, Mg + O2 ? MgO is the skeletal equation.
� Balanced chemical equation: A balanced equation is a chemical equation in which number of atoms of each element is equal on both sides of the equation i.e number ofatoms of an element on reactant side = number of atoms of that element on the product side.
. Combination Reaction :Two or more reactant combine to form a single product.
2 Mg (s) + O2 (g) ? 2 MgO Magnesium Oxygen Magnesium oxide (White ash)
(basic) turns Red litmus blue
2. Decomposition Reaction: A single compound decomposes or break down to give two or moresimpler substances.
2 FeSO4 (s).symbol of het Fe2 O3 (s) + SO2 (g) + SO3(g) Ferrous Sulphate Ferric oxide Sulphur Sulphur (green) (brown) dioxide trioxide
3. Displacement Reaction: A more reactive element [metal] displaces less reactive elemen [metal] from its aqueous salt soln Fe (s) + ZnSO4 (aq) ? FeSO4 (aq) + Zn (s) (Colourless) (green)
4. Double Displacement Reaction: Aqueous soln of two ionic compounds react by exchange of their ions is called double displacement Reaction BaCl2 (aq) + Na2SO4 (aq) ? BaSO4 (s) + 2 NaCl (aq) Pb(NO3)2 + 2 KI (aq) ? PbI2 ( ? ) + 2 KNO3 (aq)
5. Oxidation Reaction: In oxidation reaction, addition of oxygen or removal of hydrogen or loss of electron takes place. 2 Mg(s) + O2 (g) ? 2MgO (s) 2 Cu + O2 ? 2 CuO (Black ) (Copper II Oxide)
6. Reduction Reaction: In reduction Reaction addition of hydrogen or removal of oxygen or gain of electron takes place. CuO(s) + H2 (g) ?Cu(s) + H2 O (l)
7. Redox Reaction: Reaction involving both oxidation and reduction simultaneously CuO (s)+ H2 ? Cu(s) + H2 O (l).
8. Exothermic Reaction: Reaction in which heat is evolved. C (s) + O2 (g) ? CO2 (g) + Heat
10. Neutralisation Reaction : When an acid and a base react together to form salt and water. HCl (aq) + NaOH (aq) ? H2O (l) + NaCl (aq) (acid) (base) (Water) (Salt) Hydrochloric acid Sodium hydroxide Sodium Chloride
Law of Conservation of Mass
In a chemical reaction matter is conserved. Total no. of atoms = Total no. of atoms Total mass = Total mass. [While Balancing a Chemical Equation Formula of reactants and products should not be changed]. Balancing:
balancing
? Corrosion: Process of slowly reacting up of metals due to attack of atmospheric gases like O2 ,CO2M etc.
Corrosion.
Rust(hydrated Iron (III)oxide)
Prevention:Painting, Galvanization, oiling greasing.
Corrosion of Aluminium has advantage , since Al2O3 formed as a result
of corrosion act as protective layer.
? Rancidity:
Oxidation of oils or fats in a flood, resulting into a bad smell and taste.
Prevention: Adding anti-oxidants.
Vacuum Packing
Replacing air by Nitrogen
Refrigeration of food stuf
Answer:
Hi
Explanation:
Physical Change: Change in physical properties.
� Melting
� Boiling
� Condensation
� [Note- No change occurs in the identity of the substance].
? Chemical Change:
� Atoms in the reactants are rearranged to form one or more different substances.
� Old bonds are broken, new bonds are formed.
� Reactants lose their properties to form product of different properties.
4 Fe(s) + 3O2 ?2Fe2O3 (rust). Iron Oxygen Ferric oxide
? Chemical equation:
The symbolic representation of a chemical reaction is called a
chemical equation.
Features of a chemical equation:
� The reactants are written on the left hand side with a plus sign between them.
� The products are written on the right hand side with a plus sign between them.
� An arrow separates the reactants from the products. The arrow head points towards the products and indicates the direction of the reaction.
Skeletal chemical equation: A chemical equation which simply represents the symbols and formulas of reactants and products taking part in the reaction is known as skeletal chemical equation for a reaction.
For example: For the burning of Magnesium in the air, Mg + O2 ? MgO is the skeletal equation.
� Balanced chemical equation: A balanced equation is a chemical equation in which number of atoms of each element is equal on both sides of the equation i.e number ofatoms of an element on reactant side = number of atoms of that element on the product side.
. Combination Reaction :Two or more reactant combine to form a single product.
2 Mg (s) + O2 (g) ? 2 MgO Magnesium Oxygen Magnesium oxide (White ash)
(basic) turns Red litmus blue
2. Decomposition Reaction: A single compound decomposes or break down to give two or moresimpler substances.
2 FeSO4 (s).symbol of het Fe2 O3 (s) + SO2 (g) + SO3(g) Ferrous Sulphate Ferric oxide Sulphur Sulphur (green) (brown) dioxide trioxide
3. Displacement Reaction: A more reactive element [metal] displaces less reactive elemen [metal] from its aqueous salt soln Fe (s) + ZnSO4 (aq) ? FeSO4 (aq) + Zn (s) (Colourless) (green)
4. Double Displacement Reaction: Aqueous soln of two ionic compounds react by exchange of their ions is called double displacement Reaction BaCl2 (aq) + Na2SO4 (aq) ? BaSO4 (s) + 2 NaCl (aq) Pb(NO3)2 + 2 KI (aq) ? PbI2 ( ? ) + 2 KNO3 (aq)
5. Oxidation Reaction: In oxidation reaction, addition of oxygen or removal of hydrogen or loss of electron takes place. 2 Mg(s) + O2 (g) ? 2MgO (s) 2 Cu + O2 ? 2 CuO (Black ) (Copper II Oxide)
6. Reduction Reaction: In reduction Reaction addition of hydrogen or removal of oxygen or gain of electron takes place. CuO(s) + H2 (g) ?Cu(s) + H2 O (l)
7. Redox Reaction: Reaction involving both oxidation and reduction simultaneously CuO (s)+ H2 ? Cu(s) + H2 O (l).
8. Exothermic Reaction: Reaction in which heat is evolved. C (s) + O2 (g) ? CO2 (g) + Heat
10. Neutralisation Reaction : When an acid and a base react together to form salt and water. HCl (aq) + NaOH (aq) ? H2O (l) + NaCl (aq) (acid) (base) (Water) (Salt) Hydrochloric acid Sodium hydroxide Sodium Chloride
Law of Conservation of Mass
In a chemical reaction matter is conserved. Total no. of atoms = Total no. of atoms Total mass = Total mass. [While Balancing a Chemical Equation Formula of reactants and products should not be changed]. Balancing:
balancing
? Corrosion: Process of slowly reacting up of metals due to attack of atmospheric gases like O2 ,CO2M etc.
Corrosion.
Rust(hydrated Iron (III)oxide)
Prevention:Painting, Galvanization, oiling greasing.
Corrosion of Aluminium has advantage , since Al2O3 formed as a result
of corrosion act as protective layer.
? Rancidity:
Oxidation of oils or fats in a flood, resulting into a bad smell and taste.
Prevention: Adding anti-oxidants.
Vacuum Packing
Replacing air by Nitrogen
Refrigeration of food stuf