Class 9 General Science Chapter 2 Question Answer

Complete Notes of Class 9 General Science Chapter 2 Question Answer Our Life and Chemistry Notes in 9th Class General Science Urdu Medium by Sir Usman Lateef Suib. These computerized notes are very helpful in the preparation of the Our Life and Chemistry Notes for students of the Class 9 General Science Chapter 2 Question Answer these are according to the new paper patterns of all Punjab boards.

• Important Multiple Choice Questions (MCQs) and Short Questions of Chapter No.2: Our Life and Chemistry of General Science 9th class Urdu Medium.
• The Basic Building Elements for Life: In the body of living organisms, many elements are found in different quantities. In them carbon, hydrogen and oxygen have great importance. The human body also constitute these three elements. These elements combine to form organic compounds such as proteins, carbohydrates and lipids. All these compounds work as building material for the bodies of living organisms e.g. meat, pulses, fats, cooking oil, sugar, wheat etc.
• Carbon: Carbon is one of the essential part of all living things on this planet. Small quantities of carbon are found in the earth's crust as the free element. Carbon is an important element of natural compounds such as natural gas, petroleum and wood etc. Carbon is also present in the food you eat. The food containing carbon, hydrogen and oxygen are either carbohydrates (starch, sugar, cellulose) or fats (butter, oils) while the food containing carbon, hydrogen oxygen, and sulphur or nitrogen are proteins (meat, fish). All the plant life is also made up of compounds containing carbon, hydrogen and oxygen. Other carbon containing compounds are silk, soap, alcohol, plastic etc.
• Hydrogen: Hydrogen is an essential part of water (H2O) and therefore important for all living things. Other than this it is found in natural gas. It is most common element in the universe, for example the sun is a huge white-hot ball consisting almost entirely of hydrogen.
• Oxygen: Oxygen is a colourless, odourless gas which is slightly soluble in water. Fish and all form of aquatic life rely on this property. It is the major constituent of air. The various organic compounds containing oxygen are glucose, sugar, cellulose, fats, proteins etc.
• Importance of Carbon, Hydrogen and Oxygen: You have already studied that carbon, hydrogen and oxygen play important role in the living organisms. Respiration is a process which provides energy to the body while photosynthesis is a direct or indirect source of food for living beings. These three elements have basic role in these two processes.
• Respiration: Oxygen is essential for life. It plays an important role in respiration. Respiration is the process by which living things use oxygen from the air to oxidize food substances (mainly glucose) in their body cell.
• Glucose + Oxygen  ------ >  Carbon dioxide + Water + Energy
• When we breathe in, we take air into our lungs. The oxygen from the air then dissolves in the blood in our lungs. This dissolved oxygen is taken by hemoglobin to all parts of our body to react with glucose to produce energy. At the same time, carbon dioxide produced as a waste product is taken back to the lungs and breathed out.
• Photosynthesis: Photosynthesis is a process by which green plants manufacture carbohydrates (glucose) from atmospheric carbon dioxide and water from the soil, in the presence of energy of sunlight.
• Water + Carbon dioxide ------- > Glucose + Oxygen
• This process only occurs in chlorophyllous cells of the leaves and stems. Oxygen is produced in this process as a by-product and released into the atmosphere. Photosynthesis is effectively the reverse of respiration. This is also called anabolic (building up) process while the respiration process is called catabolic (breaking down) process.
• Carbon and its importance: Very small quantities of carbon are found in the earth crust as the free element. It is present in approximately one million known compounds. One of the unique property of carbon is that its atoms combine with each other to form long ring compounds.