Q.13. Some reactions are given below. Identify the chemical reaction and write the reasons :
1. Melting of Ice
2. Dissolution of sugar in water
3. Burning of wood
4. Blackening of pieces of potatoes, brinjals and apples.
5. Melting of wax.
6. Blackening of silver ornaments
7. Souring of milk.
8. Synthesis of food by green plants in presence of sunlight.
Answers
1) melting of ice is physical change
2)Dissolution of sugar in water is also physical change.
3)Burning of wood is a chemical change
4)Blackening of pieces of potatoes, Brinjals,and apples is a chemical change
5)melting of wax is a physical change
6)Blackening of silver ornaments is a chemical change.
7) souring of milk is also chemical change
8)Synthesis of food by green plants in presence of sunlight is also chemical change
Answer:
the chemical reactions are Burning of wood , Blackening of potatoes , brinjals and apples, Blackening of silver ornaments, souring of milk and synthesis of food by plants
Explanation:
Burning of wood - The physical and chemical properties and color of wood is changed to ash causing presence of both heat and light.
Blackening of pieces of potatoes, brinjals and apples. - When you eat apples or bananas, or when peeling potatoes or eggplant, the color of the fruit and vegetables becomes brown and sometimes "changes to black color, the reason is due to oxidation of phenolic compounds in the fruit under the action of an enzyme called polyphenol oxidase .
Blackening of silver ornaments - When silver objects are exposed to pollutants normally found in air, they gradually become dull and discolored. This darkening of silver is called tarnishing. It occurs when silver undergoes a chemical reaction, classified as an oxidation reaction, with sulfur-containing substances.
Souring of milk. - Milk souring is known as a chemical transition or chemical change because it ends up forming a new product that is the lactic acid, hence leaving the milk sour.
Synthesis of food by green plants in presence of sunlight. - The process by which plants make food is named photosynthesis. Photosynthesis is the process in which green plants use sunlight to make their own food. Photosynthesis requires sunlight, chlorophyll, water, and carbon dioxide gas. Chlorophyll is a substance in all green plants, especially in the leaves.