NCERT 2022 | Types of Reactions in One Shot Class 8 Science | पदार्थ : धातु और अधातु | By Amba Ma'am

Piyush is a student of class 10. His teacher was teaching the type of chemical reactions in the class. Piyush was aksed to carry out the reaction of electrolysis of water in the laboratory. Piyush set up the complete apparatus for the electrolysis of water. He took pure water (distilled water) to carry out this reaction. When Piyush passed electric current through this water for a considerable time even then no chemical reaction took place. Piyush told this problem to his classmate Arjun. Arjun thought over the problem and asked Piyush to add a little of a certain substance into pure water before passing electric current through it. When electric current was passed thorugh water after adding a little of this substance then a chemical reaction took place to form two gases X and Y . The volume of gas X collected over one of the electrodes was 8mL whreas the volume of gas Y collected over the other electrode was 16mL (a) Why no chemical reaction took place when electric current was passed thorugh pure water? (b) What substance was added in little quantity to pure water before passing electric current again? (c) How did the addition of little of this substance help in the electrolysis of water? (d) What is gas X ? Over which electrode is it collected? (e) What is gas Y ? Over which electrode is it collected? (f) What type of chemical reaction is demonstrated by this experiment ? Why? (g) What values are displayed by Arjun in this episode?

Reshma is the student of class X in a city school. One day she was sitting in the school garden with her friends during the recess. There was a tall tree at the edge of the garden having a large honeycomb attached to it. Some students were playing cricket in te school playground. Suddenly the cricket ball hit the honeycomb due to which a large numbr of honey-bees started flying here and there. Reshma was stung on her face by a honey-bee. The sting was so painful that Reshma started crying. She was immediately rushed to the science laboratory. One of her classmates Shanta gave her vinegar solution to rub on the stung area to get relief from pain. Another clasmate Amarjit, howerver, asked Reshma to rub baking soda solution on the stung area of face. On rubbing baking soda solution, Reshma felt a lot of relief from pain. (a) What kind of liquid is injected into the skin when a honey-bee stings a person? (b) Why did rubbing baking soda solution on the stung area of skin give relief from pain? (c) What type of chemical reaction takes place when baking soda solution is rubbed on the honey-bee sting area? (d) Why do you think rubbing the honey-bee sting area with vinegar could not give relief from pain? (e) Name one plant whose stinging hair on leaves inject a similar liquid to that injected by honey-bee sting and can be treated by rubbing baking soda solution? (f) What vaues are displayed by Amarjit in this episode?