CBSE ADDA

Two marks questions  1. Explain how echoes are used by bats to judge the distance of an obstacle? 2. State the special properties of ultrasound that make it useful to us .In general, how these properties are utilized. 3. Why is soft furnishing avoided in concert halls? 4. Draw a diagram depicting low pitched sound and high pitched sound and write main difference between the two? 5. Distinguish between longitudinal and transverse waves. Give one example each. 6. An explosion takes place at the moon. After what time would it be heard at the earth? Three marks questions 7. Two sources A and B vibrate with the same amplitude. They produce sounds of frequencies 1 kHz and 30 kHz respectively. Which of the two waves will have greater power? 8. Find the time period of the source of a sound wave whose frequency is 400Hz. 9. A sound wave travels at a speed of 340m/s. If its wavelength is 2 cm, what is the frequency of the wave? Will it be in the audible range? 10.

1. In our country, there are attempts to increase the height of several existing dams like Tehri and Almati, dams across Narmada. What are the reasons behind it? Ans. Dams are large water storing bodies that are usually built by government agencies across the rivers to regulate the flow of water and generate electricity. They store huge amount of water for irrigation of fields throughout the year. 2. On the banks of the river, there are several factories that are discharging effluents into the river. The pH of water sample collected from the river is found to be acidic in the range of 3.5–4.5. Name the effluents which is the most likely to cause the lowering of pH of river water. What should be the effect of pollution on the fishes of the river . Ans. Untreated sewage, garbage, some human activities like bathing, washing of clothes and immersion of ashes or unburnt corpses are the most likely causes of lowering of pH of river water. It makes the water toxic and kills the aquatic o

Fill in the blanks on Pollution of Air and Water for class 8th (VIII) 1. The contamination of air by unwanted substances which have a harmful effect on both the living and the non-living is called -----------. Ans: Air pollution. 2. The substances which contaminate the air and water are called -----         Ans: Pollutants 3. The rise in Earth’s temperature is called_______________. Ans: global warming  4. ______________accumulates in body fat and travels up the food chain. Fertilizers 5. _________________results in the death of birds & aquatic animals. Ans: oil spills 6. ____________________depletes the ozone layer. Ans: CFCs 7. _________________is a clean fuel. Ans: CNG  8. Water fit for drinking is called_________________. Ans: potable water 9. ________________is celebrated in the month of July every year Ans:  van mahotsav 10. ____________________causes acid rain.  Ans: sulphur dioxide  11. _______________________cause

Point to Remember 1. .Five measurement can determine a quadrilateral uniquely. 2. A quadrilateral can be constructed uniquely if Its four sides and one diagonal is given. Its two adjacent sides and three angles are known. Its three sides and two included angles are given. Its other special properties are known (rectangle, square, rhombus, parallelogram). Its three sides and two diagonals given. For more study Construction of quadrilateral Practice Questions (View/Read/Download) Construction of quadrilateral  CBSE Test Paper (View/Read/Download) Construction of quadrilateral  CBSE Test Paper  (View/Read/Download) 1. How many measurement s can determine a quadrilateral uniquely? Ans: 5  2. How many measurements can determine a square?  Ans: 1  3. How many measurements can determine a parallelogram uniquely?  Ans: 3  4. How many measurement can determine a rhom

MCQ By(JSunil)Based on Carbon and It’s Compound Q1. Which of the following is not a saturated hydrocarbon? (i) cyclohexane ( ii) benzene. (iii) butane (iv) isobutene Q2.The bond between two identical non metallic atom has a pair of electron? (i)un equally shared between two atoms. (ii)transferd completely from one atom to another. (iii)with identical spins (iv)equally shared between them. Q3. Covalent compounds are generally ( i)soluble in water (ii)insoluble in water (iii)ionize in water (iv)hydrolyse in water Q4. Propane with the molecular formula C3H8 has ( i) 7covalent bonds (ii) 8 covalent bonds (iii) 9 covalent bonds ( iv) 10 Covalent bonds. Q5. A hydrocarbon reacts with ammonical cuprous chloride solution to form a red precipitate .The hydrocarbon is (i) ethane (ii) ethene (iii)butane (iv)1-propyne Q6.Which of the following substance is added to denature Ethanol ? ( i)methanol (ii)pyridine (iii)copper sulphate (iv)all of

1. In our country, there are attempts to increase the height of several existing dams like Tehri and Almati, dams across Narmada. What are the reasons behind it? Ans. Dams are large water storing bodies that are usually built by government agencies across the rivers to regulate the flow of water and generate electricity. They store huge amount of water for irrigation of fields throughout the year. 2. On the banks of the river, there are several factories that are discharging effluents into the river. The pH of water sample collected from the river is found to be acidic in the range of 3.5–4.5. Name the effluents which is the most likely to cause the lowering of pH of river water. What should be the effect of pollution on the fishes of the river. Ans. Untreated sewage, garbage, some human activities like bathing, washing of clothes and immersion of ashes or unburnt corpses are the most likely causes of lowering of pH of river water. It makes the water toxic and kills the aquatic

ORAL QUESTIONS CLASS VIII MATHS TOPIC :- GEOMETRY 01.  Define a Polygon . 02. How many  sides  are  there in Quadrilateral ? 03. How many sides  are there  in Octagon ? 04. What is a regular  Polygon ? 05.  What is a Diagonal? 06. What is the sum measures  of angles  of the  Convex  Quadrilateral ? 07.  How many sides  does  Heptagon  has ? 08.  Say True / False:  The polygon  with minimum  number  of sides  is three . 09.  Tell  the formula  to  find sum of all interior  angles of a polygon. 10.  What  are  the Maximum  number  of   right  angles in  the right  angled  triangle? 11.  What is the sum of interior angles of a Parallelogram ? 12.   What  is a Parallelogram ? 13.  What  is Rhombus ? 14.  What  is Rectangle ? 15.  Name the closed  figure  with 4 sides  . 16.  What is the number of sides  in hexagon  ? 17.   How many Diagonals does  a  regular  hexagon  have? 18.   What  is the Sum of interior angles  of a Pentagon ? 19.   What is the  sum  of the me