class 9 revision paper9thCBSE TEST PAPER IS MATTER AROUND US PURE

1. Salt can be recovered from its solution by evaporation. Suggest some other technique for the

same?

2. While diluting a solution of salt in water, a student by mistake added acetone (boiling point

56°C). What technique can be employed to get back the acetone? Justify your choice.

3. Explain why particles of a colloidal solution do not settle down when left undisturbed, while in

the case of a suspension they do.

4. Smoke and fog both are aerosols. In what way are they different?

5. Name the process associated with the following

(a) Dry ice is kept at room temperature and at one atmospheric pressure.

(b) A drop of ink placed on the surface of water contained in a glass spreads throughout the water.

(c) A potassium permanganate crystal is in a beaker and water is poured into the beaker with

stirring.

(d) A acetone bottle is left open and the bottle becomes empty.

(e) Milk is churned to separate cream from it.

(f) Settling of sand when a mixture of sand and water is left undisturbed for some time.

(g) Fine beam of light entering through a small hole in a dark room, illuminates the particles in its

paths.

6. The teacher instructed three students ‘A’, ‘B’ and ‘C’ respectively to prepare a 50% (mass by

volume) solution of sodium hydroxide (NaOH). ‘A’ dissolved 50g of NaOH in 100 mL of water, ‘B’

dissolved 50g of NaOH in 100g of water while ‘C’ dissolved 50g of NaOH in water to make 100 mL

of solution. Which one of them has made the desired solution and why?

7. Why is gold alloyed with copper or silver for the purpose of making ornaments?

8. Give some examples of Tyndall effect observed in your surroundings?

9. Calculate the mass of sodium sulphate required to prepare its 20% (mass percent) solution in

100g of water?

10. How would you separate a mixture of ammonia and hydrogen?

11. Action of heat on blue vitriol is a physical as well as chemical change. Justify.

12. How would you separate a mixture of NH4Cl and I2?

13. Describe a method for separation of the constituents of gunpowder.

14. Describe how you would obtain the substances mentioned below, from the given mixtures.

a) Iodine from tincture of iodine. b) Lead chloride from a mixture of lead chloride and silver

chloride

15. Briefly describe how to separate,

i) Sulphur from a mixture of sulphur and sand. ii) Black CuO from a mixture of CuO and ZnO.

16. Fill in the blanks

(a) A colloid is a ——— mixture and its components can be separated by the technique known as

———.

(b) Ice, water and water vapour look different and display different —— properties but they are —

—— the same.

(c) A mixture of chloroform and water taken in a separating funnel is mixed and left undisturbed for

some time. The upper layer in the separating funnel will be of——— and the lower layer will be

that of ———.

(d) A mixture of two or more miscible liquids, for which the difference in the boiling points is less

than 25 K can be separated by the process called———.

(e) When light is passed through water containing a few drops of milk, it shows a bluish tinge. This

is due to the ——— of light by milk and the phenomenon is called ——— . This indicates that milk

is a ——— solution.

class 8 revision worksheet metals and non metals

Fill in the blanks:

1. Metal react with oxygen to produce ................oxides and non-metal react with oxygen to produce................oxides.
2. The presence of .............. and ..................are necessary for iron to rust.
3. ...................is used for making X-ray shields.
4. .....................non-metals is used in fluorescent bulbs to display advertisements.
5. ....................element is used for making pencil lead.
6. .....................and .....................are lustrous non-metals.
7. .....................is the only non-metals that exist as liquid at room temperature.
8. The property of metals by which it can be beaten into sheets is called.................
9. .....................metal can be cut with knife.
10. ......................non-metal is used for vulcanisation of rubber.
11. .......................metal is used in processed food packaging.
12. Process of coating metals with zinc is called.......................
13. Elements that possess properties of both metals and non-metals are called.............
14. ....................is a pure chemical substance consisting of only one type of atoms.
15. Metal react with dilute acids to form...................... and.......................
Answer: 1. Basic, acidic
2. Air, water
3. Lead
4. Neon
5. Graphite
6. Graphite, iodine
7. Bromine
8. Malleability
9. Sodium
10. Sulphur
11. Nitrogen
12. Galvanization
13. Metalloid
14. Element
15. Salt, hydrogen gas

Short answers:

1. Why is gold used for making jewellery?
Answer. Gold does not easily react with other substances. It is an unreactive metal and once polishes, it retains their shine for a long time, therefore, it is used for making jewellery.
2. What do you mean by corrosion?
Answer. Corrosion is used to describe the process by which minerals such as metals are slowly eaten away when exposed to air and moisture.
3. No gas is released when sulphur is added to dilute HCl?
Answer. No gas is releases when sulphur is added to dilute HCl because non-metals do not react with dilute HCl and sulphur is a non-metal.
4. Why are electrical cables made from copper?
Answer. Since copper is a good conductor of electricity, it is used in electrical cables.
5. Why do copper vessels develop a greenish layer when exposed to moist air?
Answer. Copper vessel gets corroded in the presence of moist air that is carbon dioxide and water to form green coating of a substance called basic copper carbonate.
6. Which non-metal is considered to be backbone of the electronics industry?
Answer. Silicon is considered to be the backbone of electronics industry.
7. Why is sodium metal stored under kerosene?
Answer. Sodium metal which react vigorously with the oxygen present in air at room temperature to form sodium oxide. Hence, sodium is stored under kerosene to prevent its reaction with oxygen and moisture present in air.
8. Write the difference between metal oxides and non-metal oxides?
Answer. Metal oxides formed are basic in nature, when dissolved in water they form bases which turn red litmus into blue whereas non-metal oxides are acidic in nature, when dissolve in water they form acids which turn blue litmus into red.
9. Silver is more likely to tarnish near a petroleum refinery than in a place far away? Explain why?
Answer. Silver does not get easily corroded in unpolluted air, however, if the air is polluted with sulphur compounds such as hydrogen sulphide then silver reacts with it to form a black coating of silver sulphide.
10. What are noble metals?
Answer. Silver and gold are present at the bottom of the reactivity series of metals. They are unreactive metals and do not react with water, acids and alkalis. They therefore, occur n free state in nature. So they are noble metals.

CLASS 8 REVISION WORKSHEET

MICROORGANISMS

Fill in the blanks:

1. ___________ bacteria causes citrus canker.
2. ___________ is a skin disease in human caused by fungus.
3. The female Aedes mosquito is a carrier of the ________virus.
4. _______, ______ are chemicals that inhibit microbial growth.
5. When an antigen enters the body, the body produce proteins called ________ to destroy it.
6. A _________ is used to study microbes.
7. ________ is a unicellular fungus.
8. ________ made the first vaccine.
9. ________ microbe is present in our intestine as a friendly microbes.
10. ________ can kill disease causing microbes without causing injury to body.
11. _________ are on the borderline of living and non- living.
12. _______and ______ are two diseases caused by bacteria.
13. In legumes, the root nodules contain the bacterium_________.
14. Yeast is added to dough to produce _________which makes the dough rise.
15. The heating of milk upto to 70*C& then suddenly cooling is called _________.
Answers:
1) Xanthomonas
2) Ringworm
3) Dengue
4) Sodium benzoate and sodium metabisulphite
5) Antibodies
6) Microbiology
7) Yeast
8) Edward Jenner
9) E.coli
10) antibiotics
11) viruses
12) cholera and Typhoid
13) Rhizobium
14) carbon di oxide
15) pasteurization

SHORT QUESTIONS

1. Name two parasitic protozoa that cause diseases in human?
Plasmodium ( Malaria), Amoeba ( Amoebic dysentery)
2. What are antibiotics?
Antibiotics can kill disease causing micro organism without causing any injury to body tissue or disturbance of the body functions. Examples: penicillin, ampicillin.
3. What is fermentation?
The process of conversion of sugar into acid or alcohol is called fermentation. Yeast is used to ferments sugar in grapes to make wine.
4. What is pasteurization? How is it useful?
Pasteurization of milk consists of heating it to high temperature of 70˚C for about n the flavor. This method was invented by Louis Pasteur.
5. What are vaccines? How does a vaccine work?
Vaccines consist of dead and weakened microbes. When these are swallowed or injected into the body of a patient, the body produces antibodies to fight them. The antibodies remain in the body and protect it from any future attack of disease germs.
6. Which microorganism acts as decomposers? How is this activity useful to us?
Microorganisms such as bacteria, fungi and protozoa help by decomposing the tissues of dead organisms to get their food. The nutrient that were taken from the soil by plants and animals and restored and are used again by living organisms.
7. Describe the role of Rhizobium in maintaining soil fertility?
Rhizobium bacteria are capable of converting the atmosphere nitrogen into nitrates and nitrites thereby increasing soil fertility.
8. What is communicable disease?
Diseases that spread from an infected person to healthy individual through air, water or direct contact is called communicable diseases.
9. Microbes will never grow food keep inside refrigerator? Do you agree why?
Rrefrigeration only delays but do not completely rule art the possibility of food spoilage. If the food is taken out of the freezer, the microbes start growing again.
10.Define- Food preservation and Food poisoning
Food preservation: Processing of food to prevent their spoilage and retain their nutritive value or long periods is called food preservation.
Food poisoning: Food has to be preserved for later use and should be kept fresh. If microbes grow on it the food gets spoilt and many cause food poisoning.

Practice Questions:

1. What is pathogen? How does it gain entry into the body of living organisms?
2. Why are bacteria and fungi said to be decomposers?
3. Give two ways in which bacteria are useful to us and two ways in which they are harmful?
4. Discuss five methods of food preservation?
5. Explain how microbes are useful to us?
6. Why are viruses considered to be the borderline between living and the non- living?
7. How do viruses cause diseases?
8. What is nitrogen cycle?
9. Which microorganism is used to make bread soft and fluffy? Discuss how this happens?
10. How does mosquito help in spreading microorganism?