Kerala SCERT Class 8 Science Chapter 6 Chemical Changes Question Answer Solution Here. Kerala Board Class 8 Students can find Here 6th Chapter Chemical Changes Notes provide by our Teacher. Important Question Answer from Chapter 6 Chemical Changes.
- Board- Kerala Board.
- Class – 8.
- Subject – Science Part 1
- Chapter – 6.
- Chapter Name – Chemical Changes.
- Topic – Question Answer Solution.
Question: (1) in case of _______ new molecules are formed and permanent change?
(a) Chemical change
(b) Physical change
Ans: – Chemical change.
Question: (2) chemical reaction which liberate or absorb light energy are known as _______?
(a) Photochemical reaction
(b) Electrochemical reaction
Ans: – Photochemical reaction.
Question: (3) _________ are substance which undergoes chemical change when electricity is passed through them?
(a) Electrolytes
(b) Electrodes
Ans: – Electrolytes.
Question: (4) the rods which are connected to the pole of battery and which transfer electricity to the electro are known as _________?
(a) Electrodes
(b) Electrolyses
Ans: – Electrodes.
Question: (5) The process in which a substance undergoes decomposition by a absorption of electrical energy is known as __________?
(a) Electrolysis
(b) Electrolyte
Ans: – Electrolysis.
Question: (6) Electroplating is an _____ reaction?
(a) Electrochemical
(b) Photochemical
Ans: – Electrochemical.
Question: (7) the chemical reaction which absorbs energy are known as ________?
(a) Endoergic reaction
(b) Exoergic reaction
Ans: – Endoergic reaction.
Question: (8) the chemical reactions which liberate heat are called__________?
(a) Exothermic reaction
(b) Endothermic reaction
(c) Endoergic reaction
(d) Exoergic reaction
Ans: – Exothermic reaction.
Question: (9) the chemical reaction which absorbs heat are called________?
(a) Exothermic reaction
(b) Endothermic reaction
(c) Endoergic reaction
(d) Exoergic reaction
Ans: – Exothermic reaction.
VERY SHORT NOTE:
Question: (1) what is electroplating?
Ans: – Electricity is used to obtain a thin coating of a particular metal on other metallic object this process is known as electroplating.
Question: (2) define photochemical reaction?
Ans: – Chemical reaction which liberates or absorbs light energy is called photochemical reaction.
Question: (3) Explain electrolysis?
Ans: – The process in which substance undergoes decomposition by the absorption of electrical energy is known as electrolysis.
Question: (4) what is electrochemical reaction?
Ans: – Chemical reaction in which electrical energy is consumed or produced are known as electrochemical reaction.
SHORT NOTE:
Question: (1) explain term electrolyte?
Ans:- Electrolyte substance which undergoes chemical change when electricity is passed through them , sodium chloride, copper , sulphate, silver nitrate etc are electrolyte. Acid, alkali and salts in their molten form as well as in aqueous solution are electrolytes.
Question: (2) what is electrochemical cell?
Ans: – Electricity is produced as chemical reaction between the acid and the metals kept immersed it, such arrangement which produce electricity as result of chemical reaction are known as electrochemical cells.
Chapter no 6 Chemical Changes
For more questions :
1.) answer the following
1) give examples of dry cell and lithium ion cell where they used.
Ans- Dry cell- Radios, cameras, clocks, toys.
Lithium ion cell- mobile phone, laptops
2) what is endoergic and exoergic reaction?
Ans- the chemical reaction which energy is absorbed is called endoergic reaction. The chemical reaction in which energy is liberated during reaction is called exoergic reaction.
3) define electrochemical reactions.
Ans- the chemical reactions in which electrical energy is consumed or produced are known as electrochemical reactions.
4) give examples of endochemical and exochemical reactions.
Ans- the examples of endo chemical reactions are the reaction in which heat is absorbed example- photosynthesis, evaporation of liquid, melting of ice etc.
Exochemical reaction means heat is liberated example- combustion.
5) give any three examples of physical and chemical change.
Ans- chemical changes- burning of wood, rusting of bicycle tyre, cooking food.
Physical changes- melting of ice, freezing of water, bending the object etc
2.) answer the following in short.
1) what is photochemical reactions? Explain the photosynthesis.
Ans- the chemical reaction which liberate or absorb light energy are known as photochemical reactions. Photosynthesis is a chemical reactions that is responsible for sustaining life on earth. In this reaction , plants produced glucose by absorbing light.
Water + carbon dioxide+ light —- Glucose + oxygen
The glucose is formed is stored by plants in the form of starch.
2) Bioluminescence, write note.
Ans- light produced by a fire fly is the result of a chemical reactions that happens in its body. Light energy is emitted as a result of the formation of oxyluciferin through the reaction between luciferin and oxygen in the presence of luciferase ,m an enzyme present in the fire fly’s body. This phenomenon is known as Bioluminescence. 95% of the energy liberated in this process is in the form of light . this is the reason why heat is not felt when a fire fly glows.
3) what is electrolysis? Explain about elctrolytes.
Ans- electrolysis is the chemical procedure in which the substance undergoes decomposition by the absorption of electrical energy is known as electrolysis. The electrodes or electrolytes are sodium chloride, copper, suplphate, silver nitrate etc. are electrolytes. Acids , alkalis and salts in their molten form as well as in aqueous solutions are electrolytes. The rods which are connected to the poles of a battery and which transfer electricity to the electrolyte are known as electrodes.
4) what is electroplating?
Ans- when electricity is used to obtain a thin coating of a particular metal on other metallic objects this process is known as electroplating. Electroplating is electrochemical reaction.
5) write different types of cell and the instrument in which it is used.
Ans- there are different types of cells are used like
cell |
Instrument in which it is used |
Dry cell | Radios
Cameras Clocks Toys |
Mercury cell | Watches
Calculators Electronic insturments |
Nickel cadmium cell | Rechargeable torches
Cameras |
Lithium ion cell | Mobile phone
Laptops |
6) write note on charged particles.
Ans- aqueous solution of salts , acids and alkalies contain positively charged particles and negatively charged particles. This is why they are set free at the negative and positive electrodes respectiviely during electrochemical reactions. The chemical formula of the compounds formed by the ions can be obtained , depending on the charges possessed by the ions. The example of ions are-
Positive ion- Na+, k+, Ca2+
Negative ion- O2-, NO3-
7) write example positive and negative ion.
Ans-
Positive ion | Negative ion |
Na+ | Cl- |
K+ | HCO3- |
Zn2+ | NO3- |
Mg2+ | CO3 2- |
Ca2+ | O2- |
8) write a note on a battery made of lemons.
Ans- for making a battery of lemons follow the procedure as follows- Take a few lemons and in each one of them, fix a copper rod and a zinc strip. Conncet the zinc strip of one lemon to the copper rod of the next lemon. Connect the copper rod on the first lemon and the zinc strip on the last lemon to an LED using a conducting wire. The LED glows. This happens because the lemon contain acids and electricity is produced here by the reaction of these acids with metals. The reaction is above in which chemical reaction sin which electrical energy is consumed or produced are known as electrochemical reactions.