Page 236 - ICSE Chemistry 8

29. ______________ reac ons occur when the electricity is passed through the reactants.
30. The decomposi on brought about by heat is called ______________ decomposi on.
31. Magnesium reacts with hot water, libera ng ______________ and forming ___________________.
32. ______________ is a mixture of carbon monoxide and hydrogen.
33. Hydrogen combines with carbon to form compounds called __________________.
34. Hydrogen is used extensively in the produc on of ____________ by Haber’s process.
35. Hydrogen is used in the produc on of ________________ which is a high temperature fl ame used
for cu ng and welding of metals.
36. ______________ maintains the level of water in the water table.
37. The level of water under the ground is called ______________.
38. ______________ is the simplest way of purifying water.
39. ______________ refers to the amount of solute that dissolves in a par cular solvent at a given
temperature to form a saturated solu on.
40. A ______________ is a heterogeneous solu on which consists of solid par cles having par cle size
above 10,000 Angstrom.
41. The compounds of carbon of biological origin are called ______________ compounds.
42. The phenomenon of existence of an element in more than one form in the same physical state is
called ______________.
43. ______________ charcoal is the purest form of carbon.
44. ______________ is a complex mixture of hydrocarbons and some free carbon.
45. ______________ is used to manufacture aerated drinks.

B. State whether the given statements are true (T) or false (F).
1. Ma er exists in three states: solid, liquid and gas.
2. The par cles of ma er are closely packed in gases.
3. Liquids tend to evaporate when le exposed to air.
4. Solids possess weak intermolecular forces.
5. Mass of an element at the start of a chemical reac on will be equal to the mass of the element at
the end of the chemical reac on.
6. We cannot obtain the original substance by reversing the ac on in an irreversible change.
7. Ripening of fruits is an undesirable change.
8. Natural changes occur naturally on their own.
9. During physical changes, new substances are formed.
10. Boiling is a process by which a substance changes from the liquid state to the gaseous state when
heated to its boiling point.
11. A pure substance has defi nite mel ng and boiling points.
12. Filtra on is used to separate bu er from milk.
13. A separa ng funnel can be used to separate a mixture of oil and water.
14. We can separate the components of ink which is a mixture of diff erent dyes by frac onal dis lla on.
15. Chromatography is an eff ec ve method to test the purity of a sample.
16. A proton is an integral part of an atom.
17. The isotopes of elements show diff erent chemical proper es because they have same atomic
number.
18. Atoms can combine either by transferring electrons or by sharing electrons.

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