Unit 5, Chemical reation-Class 8th General Science

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Unit 5. Class 8 General Science

Class 8th General Science Unit 5 Chemical Reactions

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1. Pure substances are of .... types; elements and Compounds

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2. Element is the simplest and pure form of ..... and contains the same kind of .....

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3. Compound is formed by the chemical combination of two or more

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4. The process of formation or breaking of a chemical compound is called

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5. Substances which combine with each other are called

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6. Lime water (calcium carbonate) on thermal decomposition gives quick lime Cao and

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7. CaCo3 ------>+heat   CAO +..........

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8. 6CO2+6H2o ------>+sunlight--> C6H12O6 glucose + .........

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9. Combination of two hydrogen atoms and two oxygen atoms is broken,a new combination of two hydrogens and one oxygen atom is formed.

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10. Law of conversation of mass presented by French chemist

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11. "Mass can neither be created nor destroyed during a chemical reaction" according to which law

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12. Mass of Reactant = Mass of

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13. During a chemical reaction, the total mass of products is equal to the total

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14. 4Fe + 3O2 ------>

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15. Elements are represented by symbols and chemical compounds are represented by

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16. In a chemical equation, reactants are written on the left hand and products on the

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17. The number of atoms of each element must be equal on both sides of a

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18. The simplest method for balancing of chemical equation is

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19. Chemical reactions can be categorized into four basic types. Addition or synthesis reactions, decomposition reactions. Double displacement reactions and

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20. Two or more substances react together to form one product

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21. One reactant which breaks up to form two or more products and are exothermic

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22. More reactive element displaces a less reactive one from its compound

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23. Involve the exchange of ions between two compounds

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24. The heat involved or absorbed during a chemical reaction is called

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25. Our body temperature is constant at 37 °C due to biochemical reactions which are absorbed or

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26. Two types of reactions with respect to energy change e.g endothermic reactions and

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27. All those chemical reactions in which heat is absorbed during chemical reactions are known as

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28. Endo means inside, Exo means outside and therm means

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29. All those chemical reactions in which heat is released during a chemical reaction are known as

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30. The reaction between sodium and chlorine to form sodium chloride is

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