7 SCIENCE MOST IMPORTANT QUESTION

Q1. Which of the following are used for the safe disposal of human excreta in those areas where sewerage system does not exist and water supply is limited or not available at all? 1) Septic tank toilets 2) Chemical toilets 3) Composting toilets 4) Vacuum toilets Solution A composting toilet is a self-contained human waste disposal unit which is not connected to a sewer line. It breaks down and dehydrates human waste to a compost which can be added to soil to make it fertile.  Q2. Name any three water borne diseases Solution Water-borne diseases include cholera, typhoid, polio, meningitis, hepatitis etc. (Any three) Q3. Why it is that cooking oil and fats should not be thrown down the drain? Where should they be thrown? Solution Cooking oil and fats should not be thrown

Q1. Name any four useful products other than wood, which we get from forests Solution Four useful products which we get from forests are rubber, paper, gum, spices, etc. Q2. (a) What is the importance of humus? (b) What happens if an animal dies in the forest? (c) Give an example of a food chain. Solution (a) The presence of humus ensures that the nutrients of the dead plants and animals are released into the soil. From there, these nutrients are again absorbed by the roots of the living plants. (b) The dead animals become food for vultures, crows, jackals and insects. In this way, the nutrients are recycled. (c) Grass   insects frog snake eagle Q3. Why forests are called green lungs? Solution Plants release oxygen through the process of photosynthesis which helps the animals for respiration. They also maintain the balance of oxygen and carbon dioxide in the atmosphere. That is why the forests are called green lungs. Q4. How does forest protect the

Q1. What do you understand by aquifer? Solution At some places the groundwater is stored between layers of hard rock below the water table. This is known as an aquifer. Q2. The groundwater stored between the layers of hard rock below the water table is known as 1) Water table 2) Water peak 3) Aquifer 4) Infiltered water Solution The groundwater stored between the layers of hard rock below the water table is known as aquifer. Q3. Wastewater generated in hospitals primarily consists of 1) Plastic 2) Dead debris 3) Radioactive substances 4) Acids and bases Solution Wastewater from hos

Q1. The phenomenon that light travels in straight lines is called ________. 1) reflection of light 2) refraction of light 3) rectilinear propagation of light 4) dispersion of light Solution The phenomenon that light travels in straight lines is called rectilinear propagation of light. Q2. What is dispersion of light? Solution Dispersion of light is the splitting of light into its component colors on passing through a dispersive medium e.g. prism. Q3. If half part of a convex lens is covered, the focal length ___________ and the intensity of image __________. 1) does not change, remains same 2) does not change, decreases 3) changes, remains same

Q1. A switch is a device that is : 1) used to allow current to flow in an appliance 2) used to allow current to flow in the circuit or in an electrical appliance and to cut it off when desired. 3) used to allow current to flow in the circuit 4) used to cut off  the flow of current Solution A switch is a device that is used to allow current to flow in the circuit or in an electrical appliance and to cut it off when desired. Q2. Give two uses of electromagnets. Solution Two uses of electromagnets are: Electromagnets are used in the construction of a large number of devices like electric bells, loudspeakers, electric motors, electric fans, etc. Electromagnets are used by doctors to remove tiny iron pieces from the eyes of a person (which may have fallen into the eyes accidently).

Q1. Which of the two is moving faster (a) A car going over a distance of 100 km in 5 hours, or (b) A train covering a distance of 300 km in 6 hours? Solution Speed of the car = 100/5 = 20 km/h. Speed of the train = 300/6 = 50 km/h. Hence train is moving faster than the car. Q2. The time between one new moon to the next is called? 1) A month 2) A week 3) A year 4) A day Solution The time between one new moon to the next is called a month. Q3. Who found that a pendulum of a given length takes always the same time to complete one oscillation? 1) Newton 2) Galileo Galilie 3) Archimedes 4) Albert Einstein

Q1. The petals attract insects for pollination. 1) False 2) True Solution True Q2. Name three hard fruits. Solution Walnuts, almonds and peach are examples of hard fruits Q3. (a) What do you understand by seed dispersal?(b) What happens to the seeds when fruits burst with sudden jerks? Solution (a) Seed dispersal refers to spread of seeds away from parent plant to a new growing location in order to prevent overcrowding.(b) When the fruits burst with sudden jerks, the seeds are dispersed and are scattered far from the parent plant. Q4. Maple seeds are dispersed by _____________ Solution wind Q5. New plants can be obtained from the stem or branch of an existing plant by a method called _______________ Solution cutting Q6. Plants benefit by _______________ Solution seed dispersal Q7. What is self-pollination? Diagrammatically repr