std 8 question paper the General science first term

Q 1         Answer in brief.
        1  What is the relation between the number of valence electrons and valency ?
        2. State the merits of Whittaker's method of classification ?
        3. Which are the various media of spreading the infectious diseases ?
        4. How much pressure do we carry on our heads ? Why don't we feel it ?
        5. What would have happened ? if RBCs had mitochondria ?
        6. Plants synthesize glucose in sunlight with the help of Chlorophyll from carbon dioxide and                     water give  away oxygen. Identify 4 compounds in this process.
        7. What are the adverse effects of corrosion ?
        8. Explain the relation between continuous rains and landslides.
        9. Give the preventive measures of cancer.
        10. How does the pollution occur due to vehicles ? Give the names of vehicles causing least                         pollution.
        11. What are pollutants ?
        12 A battery is to be formed by joining 3 dry cells with connecting wires. Show how will you                     connect the wires by drawing a diagram.

Q 2         Differentiate between
        1. infectious diseases and non-infectious diseases
        2. Solids and liquids
        3. Protons and electrons
        4. Compounds and mixtures
        5. Thomson's atomic model and Rutherford's atomic model

Q 3         Give reasons
        1. It is safer to find shelter under this like a bed, table at the time of earthquake.
        2. Copper and brass vessels are cleaned with lemon.
        3. Sodium metal is kept in kerosene.
        4. A solid matter has the properties of definite shape and volume.
        5. Lemon sherbet has sweet, sour and salty taste and it can be poured in a glass.
        6. Atom is electrically neutral.
        7. Fruits can be easily cut with a sharp knife.

Q 4         Solve the following numerical.
        1. The density of a metal is 7.8 * 10 cube kg / m cube. find the relative density of the metal  (                     density of water = 10 cube kg / m cube)
        2. The area of the bottom of a tiffin box is 0.25 m square and weight is 75 N. Calculate the                         pressure exerted by the box on shelf.
        3. atomic number of sodium is 11 and atomic mass number is 23. calculate the number of electrons             and neutrons of sodium.
        4. A chlorine atom contains 17 protons and 18 neutrons. what is the atomic number and atomic                     mass number for it.
        5. Volume of an object is 20 cm cube and the mass is 40 kg. Density of water is 1g/cm cube. will t            he object float on water or sink in water ?

Q 5         Draw the diagrams and label it.
        1. Structure of plant          2. Diagrammatic sketch of electronic configuration of Argon
        3. Structure of fungi