Page 241 - ICSE Chemistry 8

30. ________________ oxides can react with both acids and bases to form salt and water.
31. An atom of hydrogen consists of one __________ around which one __________ revolves.
32. Hydrogen reacts with certain highly reac ve metals at a high temperature to form salt-like compounds
called ________________.
33. ________________ is used as a fuel in rockets and guided missiles.
34. Hydrogen is used as a ______________ agent in metallurgy to extract pure metals from their oxides.
35. ______________ and ______________ are some hydrogen-based fuels.
36. A solu on in which some more solute can be dissolved at a specifi c temperature is called
________________ solu on.
37. A ____________ is an opaque but homogeneous solu on in which the solute size is between 10 and
1000 Angstrom.
38. ____________ substances absorb moisture from air which is not suffi cient to form solu ons.
39. The water that forms lather easily with soap is called _____________.
40. Water which contains bicarbonates of ____________ and ___________ is called temporary hard
water.
41. The reason for the presence of a large number of carbon compounds is its ____________.
42. Carbon exists in two allotropic forms – ______________ and ______________.
43. Diamond is ______________ in all solvents.
44. ______________ charcoal is used to refi ne crude oil for the produc on of petroleum jelly.
45. ______________ is defi ned as the increase in the average temperature of the earth’s atmosphere.
B. State whether the following statements are true (T) or false (F).
1. Gases take the shape and volume of the container they are placed in.
2. Ma er consists of large number of ny par cles which could be atoms or molecules.
3. The par cles of liquids are closely packed.
4. The kine c energy of the par cles in gases is suffi cient to overcome the interpar cle forces of
a rac on thus enabling the par cles to move away from each other.
5. The reactants take part in a chemical reac on to form new products but the total mass remains
constant.
6. Burning of paper is a fast change.
7. Change of mass occurs during a physical change.
8. Glowing of an electric bulb on the passage of electric current is a physical change.
9. The composi on of a substance changes during a chemical change.
10. Fermenta on of dough is a physical change.
11. A mixture has defi nite composi on.
12. The cons tuents are distributed non-uniformly in a heterogenous mixture.
13. The principle of sieving is the diff erence in size of the components of a mixture.
14. A mixture of sand and sawdust can be separated by winnowing.
15. We can obtain pure sugar from its solu on in water by crystallisa on.
16. All atoms of a par cular element are iden cal in mass and other proper es.
17. An atom is posi vely charged.
18. A force of a rac on exists between the electrons and protons present within the atom.
19. The valence shell of an atom cannot have more than 10 electrons.
20. Sodium donate one electron to become sodium ion.

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