CBSE ADDA

7th WASTE WATER STORY Q1. State various uses of water. Ans. Water is used for: • Drinking • Cooking • Washing clothes, utensils • Generating electricity • Bathing • Habitat for various organisms etc. Q2. What is waste water? Ans. The dirty water which contains various impurities like dust, polythene bags, Vegetable peels, kitchen waste, oil & water that goes down the drains from sinks, showers, toilets, laundries etc is waste water. Waste water can not be used further. Q3. What are the various causes of water pollution? Ans. water is polluted by various factors like: • Bathing of cattle in river bodies. • Washing of clothes & utensils by people in rivers. • Discharging wastes from factories, industries in nearby river bodies & ponds. Q4. When is World Water Day celebrated? Ans. World Water Day is celebrated on 22nd March. Q5. What is sewage? Ans. The waste water that is being generated at homes, industries, agricultural activities, human a

Objective type Questions: 1. Out of convex mirror and concave mirror, whose focus is situated behind the mirror? Ans: The focus of convex mirror is situated behind it. 2. For what position of an object, a concave mirror forms an enlarged virtual image? Ans: Object between pole (P) and focus (F) of the concave mirror. 3. If the focal length of a concave mirror is 25cm. What is its radius of curvature? Ans: Focal length = Radius of curvature / 2 25 = R / 2 R = 25 X 2 = 50cm. 4. A ray of light falls on a mirror normally. What are the values of angle of incidence and the angle of reflection? Ans: Both angle of incidence and the angle of reflection are zero. 5. What is the focal length of a plane mirror? Ans: Infinite. 6. Which spherical mirror is called a divergent mirror? Ans: A convex mirror is called a divergent mirror. 7. What is the angle of incidence, when a ray of light falls on the spherical mirror from its centre of curvature? Ans: The angle of incidence is zero, w

REPRODUCTION IN PLANTS CLASS7th CORE ASSIGNMENT Q1. Describe the different methods of asexual reproduction . Give examples. A.There are different methods by which plants reproduce asexually. They are vegetative propagation, budding,fragmentation and spore formation. The vegetative parts of a plant are the roots, stems and leaves. When new plants are produced from these parts, the process is called vegetative propagation. 1. Budding- A bulb like projection grows on the parent organism. It grows and may eventually break away from the parent. E.g. yeast, hydra, corals, sponges. 2. Fragmentation- The organism breaks up into two or more fragments after maturation. These fragments grow into new individuals. E.g. spirogyra, hydra 3. Spore formation- A spore is a tiny, spherical and unicellular body protected by a thick wall. Under favourable conditions, a spore germinates and develops into a new individual. E.g. mosses, ferns, moulds Q2. Describe the various ways by which seeds are disp

OBJECTIVES OF THIS LESSON Periodic Classification of Elements After completing this lesson, you will be able to: ! state different historical classifications of elements in brief; ! state main features of Mendeleev’s periodic table; ! explain the defects of Mendeleev’s periodic table; ! state modern periodic law; ! describe the features of the long form of periodic table; ! define various periodic properties; ! discuss the trends in various periodic properties in the periodic table. The first classification of elements was as metals and non-metals. This served only limited purpose mainly because of two reasons: 1. All the elements were grouped in to these two classes only. The group containing metals was very big. 2. Some elements showed properties of both-metals and non-metals and they could not be placed in any of the two classes. Dobereiner’s triads In 1829, Dobereiner, a German scientist made some groups of three elements each and called them triads.He obs