8th Combustion and Flame CBSE Test Paper

Science CLASS – VIII COMBUSTION AND FLAME
Q.1 Name a few fuels used in our homes.
Q.2 Name a few fuels used in trade and industry.
Q.3 What fuels are used for running automobiles?
Q.4 What is the difference between the burning of a candle and burning of a fuel like coal?
Q.5 What is combustion?
Q.6 Define a fuel?
Q.7 (i) What are the essential conditions required for combustion?
(ii) What is the essential condition required for extinguishing fire?
Q.8 What are inflammable substances?
Q.9 In what form is LPG stored in cylinders?
Q.10 Name the most common fire extinguisher?
Q.11 Water is not suitable for extinguishing fires involving electrical equipment oil and petrol. Why?
Q.12 Explain how CO2 is able to control fires?
Q.13 What are the requisites (qualities) of a good (ideal) fuel?
Q.14 Explain the following terms:-
(i) Global warming
(ii) Acid rain

Q.15 Suppose you are asked to boil a given quantity of water using cow dung  cake, coal and LPG as fuels. Which fuel would you prefer? Give your reason.
Q.16 Define calorific value of a fuel. Though hydrogen has got highest calorific value but it is not used as a domestic fuel. Why?
Q.17 Make a labeled diagram of a candle flame.
Q.18 Name various types of combustion. Give example of each type?
Q.19 Differentiate between.
      (a) Combustible and non combustible substances
      (b) Complete combustion and incomplete combustion.
      (c) Luminous and Non-luminous flames.
Q.20 Define the term ignition temperature. Why substances like alcohol and petrol are called inflammable substances? 

VIII:Coal and Petrolium CBSE Test Paper

Q.1 Fill in the blanks:-
(i) On heating in air, coal mainly produces ________ gas.
(ii) ________ is an almost pure form of carbon.
(iii) Coal tar is a mixture of about ________ substance..
(iv) Now a days ________, a petroleum product is used in place of _______for metalling the roads.
(v) ________ is used as a fuel in light automobiles whereas heavy motor vehicles run on ________.
Answer these questions

Q.2 What are natural resources?
Q.3 Give three examples of natural and man-made material?
Q.4 What are the two kinds of natural resources? Explain giving examples?
Q.5 What are fossil fuels? Give three examples?
Q.6 Write two uses of coke?
Q.7 Name four substances which are manufactured using products obtained from coal tar?
Q.8 How is petroleum formed?Q.9 Name three places in India where petroleum oil is found.
Q.10 What is petroleum refining?
Q.11 Write two uses of petrol, kerosene, diesel, paraffin wax and bitumen?
Q.12 Why is CNG being used as a fuel for vehicles?
Q.13 Explain why should we use fossil fuels only when absolutely necessary.
Q.14 What is the full form of LPG and CNG?
Q.15 What are the tips given by PCRA to save petrol and diesel?
Q.16 Why is petroleum called black gold?
Q.17 Give two advantages of natural gas as a fuel.
Q.18 Explain why coal, petrol and diesel oil will be exhausted one day.
Q.19 Write any two ways in which we can conserve fossil fuels.
Q.20 Write three ways in which we can help to meet energy crisis.
Q.21 Why are petrol, coal called non-renewable resources?
Q.22 What are the advantages of using inexhaustible resources of energy?
Q.23 Write the composition of natural gas.

CBSE: VIII Ch.Synthetic FIbres and Plastics Test paper

Q1. Fill in the blanks:- Ch.Synthetic Fibers and Plastics
1. Clothes are made up of ______________ which are made from __________.
2. The polymer cellulose is made up of a large number of __________units.
3. Silk fibre is obtained from _____________ whereas artificial silk is obtained by chemical treatment of __________.
4. The polymer polyester is made up of repeating units of ______________.
5. Synthetic fabrics soak ________ water than the natural fabrics and take__ time to dry.(less/more)
6. Polythene which is used to make polythene bags is an example of a ________.
7. Iron rusts when it is exposed to ______________ and _____________.
8. Plastics do not react with ______________ and __________________.
9. Plastics are generally ___________________ than metals.
10. ________________ is a special plastic on which oil and water do not stick.

Q2. Answer the following:
1. Define a polymer.
2. Name a few synthetic fibres.
3. List the unique characteristics of synthetic fibres which make them popular dress materials.
4. Explain why plastic finds such a variety of uses.
5. Differentiate between thermoplastics and thermosetting plastics.
6. List the three characteristic properties of plastics.
7. What are the advantages of using a plastic container?
8. Why do electrical wires have plastic covering?
9. Why recycled plastic should not be used for storage of food?
10. Differentiate between a biodegradable and a non-biodegradable material

Synthetic Fibre And Plastics
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Class–IX CHEMISTRY Chapter-2:IS MATTER AROUND US PURE

Separating the Components of a Mixture
Importance of separation--> To study and to use the individual components of a mixture

Q. What would happen if you were to take a saturated solution at a certain temperature and cool it slowly. 

Ans. Different substances in a given solvent have different solubilities at the same temperature. So on cooling substances start to precipitate out.

Q. What is suspension?Write its properties?

Ans: Suspension:Non-homogeneous systems, in which solids are dispersed in liquids, are called Suspensions so It is a heterogeneous mixture.

Properties of a Suspension---

• Suspension is a heterogeneous mixture.

• The particles of a suspension can be seen by the naked eye.

• The particles of a suspension scatter a beam of light passing through it and make its path visible.

• The solute particles settle down when a suspension is left undisturbed, that is, a suspension is unstable.

* They can be separated from the mixture by the process of filtration.

Q. How can we separate colour component of from ink(mixture.)?

Ans: By evaporation method: Water (Solvent) has got evaporated and residue color left over.

Conclusion: we can separate the volatile component (solvent) from its non-volatile solute by the method of evaporation.

Q. How can we separate cream(fat)  from milk ?

Ans: The denser particles of water are forced to the bottom and the lighter particles of cream/fats stay at the top when milk spun rapidly by centrifuge machine.

Centrifugation: Applications-

• Used in diagnostic laboratories for blood and urine tests.

• Used in dairies and home to separate butter from cream.

• Used in washing machines to squeeze out water from wet clothes

Q. How can we separate kerosene oil from water?

Ans: By using a separating funnel.

The principle is that immiscible liquids separate out in layers depending on their densities.

Applications 

• To separate mixture of oil and water.

• In the extraction of iron from its ore, the lighter slag is removed from the top by this method to leave the molten iron at the bottom in the furnace.

Q. How can we separate mixture of salt and ammonium chloride?

Ans: By sublimation method sice ammonium chloride is a sublimating substance

Q. How can we separate dye in black ink?

Ans: Dye in black ink is a mixture of different compounds.

These different compounds can be separated by chromatography method.

The process of separation of components of a mixture is known as chromatography.

Kroma in Greek means colour. This technique was first used for separation of colours, so this name was given.

Chromatography is the technique used for separation of those solutes that dissolve in the same solvent.

Applications: To separate

• colours in a dye • pigments from natural colours • drugs from blood.

Q. What according to you, can be the reason for the rise of the coloured spot on the paper strip?

Ans. The ink that we use has water as the solvent and the dye is soluble in it. As the water rises on the filter paper it takes along with it the dye particles. Usually, a dye is a mixture of two or more colours. The coloured component that is more soluble in water, rises faster and in this way the colours get separated

Further study search related
Jsunil's Chemistry for Class IX - is matter around us pure solved questions 
How to separate,
i) Sulphur from a mixture of sulphur and sand. 
ii) Black CuO from a mixture of CuO and ZnO.
iii) mixture of NH4Cl and I2 iv)the constituents of gunpowder
v) a mixture of ammonia and hydrogen

Is Matter around Us Pure

CBSE chapter-wise MCQ Multiple Choice Questions, Test Paper, Sample paper   based on CCE pattern for class 9 science Is Matter around Us Pure. Elements, compounds and mixtures. Heterogeneous and homogenous mixtures, colloids and suspensions.

MCQ: Fill in the blanks: Acid base and salt d salt

MCQ	Fill in the blanks:  Acid base and salt d salt
1.	The substances whose aqueous solution change the blue litmus to red ------------------Acids
2.	The substances having a tendency to lose one or more protons are called: ------------   Acids
3.	The substances which donate the pair of electrons for bond formation, are known as:-------     Base
4.	When equivalent quantities of acid and base are mixed, salt and water are formed, the reaction is termed as:----------- Neutralization
5.	The acids which contain one acidic hydrogen are called:-------- Mono-protic
6.	The number of acidic hydrogen atoms present in a molecule of an acid is called: ----  Basicity
7.	The number of replaceable [OH] ions present in a molecule of base, is called: ---    Acidity
8.	An acid that produces large number of (H) ions in aqueous solution is called: ---------Strong acid
9.	An ionic compound, that is formed when an acid neutralizes a base, is called:------ Salt
10.	SaIts that formed by the reaction of strong acid with weak base are:----Acidic
11.	Alums are example of  ---------salt:               Double salts
12.	The formula of Washing Soda is                                                  Na₂CO₃ 6H₂O
13.	Acids are the substances which give H+ ions aqueous solution, is the concept of:   Arrhenius
14.	Arrehenius theory of acid-base is not applicable in:     non — aqueous solution
15.	According to the Arrhenius concept, the strength of acid or base is based on their:   -------- a. rates of ionization          b. rates of dissociation
16	According to Bronsted — Lowry concept, a base is a substance which acts as:      a proton acceptor(NH₃)

CBSE ADDA: Chemistry:MCQ:Acid base and salt: For Olympiads

Multiple-Choice Questions: Acid base and salt

1.  The word acid comes from the Latin word ‘ acere ‘ which means

a)      Sweet

b)      Salty

c)      Neutral

d)      Sour

2. Substances which are bitter in taste, feel soapy on touching are known as

a)      Acids

b)      Bases

c)      Indicators

d)      Neutral solution

3. Special type of substances used to test whether a substance is acidic/basic are known as

a)      Indicators

b)      Acids

c)      Bases

d)      Salt

4. Some naturally occurring indicators are

(a). Turmeric

(b)  Litmus

©. China rose

(d). All the above

5.The most commonly used natural indicator’ Litmus’ is extracted from

(a).Lichens

(b). Turmeric

©. Indicators

(d). China rose

6. Litmus is available in the form of

(a). Litmus paper

(b) Lichens

©   Indicator

(d). China rose

7. Neutral solutions which do not change the colour of either red/blue litmus are known  as

(a).Neutral solutions

(b) Acid solutions

©. Basic solutions

(d). Neither acidic nor basic

8. Acetic acid is found in

(a).Curd

(b). Spinach

©  Citrus fruits

(d). Vinegar

9. Formic acid is found in

a). Curd

(b). Spinach

©. Ant’s sting

(d) Ascorbic acid

10. Citric acid is found in

(a). Curd

(b). Citrus fruits

©. Ascorbic acid

(d). Lime water

11. Lactic acid is found in

(a). Curd

(b).Citrus fruits

©.Gooseberry

(d)Lime

12. Oxalic acid is found in

a)      Spinach

b)      Curd

c)      Oranges

d)      Unripe mangoes

13. Ascorbic acid is found in

(a). Amla & Citrus fruits

(b) Curd

©.  Oranges & lemon

(d).Unripe mangoes

14. Tartaric acid is found in

(a). Tamarind

(b) Grapes

©  unripe mangoes

(d)All of the above

15. Calcium hydroxide is found in

Calcium carbonate

Calcium chloride

Calcium

Lime water

16. Ammonium hydroxide is found

(a).Window cleaner

(b).Detergents

(c)  Soap

(d). Milk of magnesia

17. Sodium hydroxide is found in

a)      Soap

b)      Window cleaner

c)      Calcium hydroxide

d)      Sodium

18. Potassium hydroxide is found in

(a). Soap

(b). Window cleaner

© Potassium

(d)Potassium chlorate

19. Magnesium hydroxide is found in

(a). Milk of magnesia

(b).Magnesium chloride

(c)  Magnesium ribbon

(d) Magnesium hydroxide

20.Which of the following salts is basic in nature?

(a) NH4NO3

(b) Na2CO3

(c) Na2SO4

(d) NaCl

Answer

1. D         2  b          3. A              4. D            5. A            6. A          7. A        8. d

9. C           10. b      11. A          12. A          13. A           14.  D         15. d         16. A

17. A      18. A             19.a         20 B

X : 10th Acid Base and Salt:Solved Edugain questions

Q. 1.  What happens if sodium hydroxide is added to cupper  ammonium sulphate solution and what is the inference?

Answer:  When sodium hydroxide is added to cupper  ammonium sulphate solution, no blue precipitate of Cu(OH)₂ is seen, which is normally observed for Cu²⁺ ion. Hence it is an example of a complex salt.

Q 2. When lead dioxide reacts with concentrated HCl and produces a salt and water, the reaction is not called a neutral reaction why?

Answer:  For a reaction to be called a neutral reaction the products should be only salt and water. But in the above reaction, Cl₂ gas is also liberated.

Q 3.Define a base and acid in terms of proton.

Answer:  A base is a proton acceptor and an acid is a proton donor.

Q 4. Answer these: 
 1) Name the anions that can be detected in the laboratory using dilute HCl or dilute H₂SO₄ and give the ionic equation common to both reactions.  
2) Which property of the acid is indicated?

Answer:  

Carbonate and Bicarbonate Ions      2H⁺  + CO₃^{2-  ........>}   H₂O + CO₂ ­


Q 5.   1) What do you observe when concentrated H₂SO₄ is added slowly to blue CuSO₄ crystals in a test tube and why? 

2) Is these any other way of observing the above result?

Answer:  1) The blue crystals turn to white amorphous anhydrous powder. Hence concentrated H₂SO₄ acts as a dehydrating agent, removing the water of crystallization molecules from CuSO₄.5H₂O crystals. 

Q6: Name two crystalline salts that do not have water of crystallization.

Answer:  The chlorides of K, Na and Pb and the nitrates of K, Na, Pb, Ag, [NH₄⁺] do not have water of crystallization.

Q 7. Why do acids not show acidic behavior in the absence of water?

Ans: Acids do not show acidic behaviour in absence of water because the dissociation of hydrogen ions from an acid occurs in presence of water only. It is hydrogen ions that are responsible for the acidic behaviour.  

Q 8. How is NH₄OH used as a laboratory reagent?

Answer:  NH₄OH is used to detect cations in their salt solutions by precipitating their hydroxides whose colour and solubility in excess NH₄OH, identifies them. 

Q 9. Name four gases that can be prepared in the laboratory using dilute H₂SO₄. Show how they can be prepared?

Answer:  The four gases are:
 1) H₂ gas            2) CO₂ gas         3) SO₂ gas       4) H₂S gas 

Their respective methods of preparations are: 

2) Any carbonate salt and dilute H₂SO₄ gives CO₂ gas.

3) Any sulphite salt and dilute H₂SO₄ gives SO₂ gas. 
4) Any sulphide salt and dilute H₂SO₄ gives H₂S gas.

Q 10. While diluting concentrated H₂SO₄, what care must be taken and why?

Answer:  While diluting concentrated H₂SO₄ never add water to concentrated acid; instead, add concentrated H₂SO₄ slowly with stirring to the volume of water. As this reaction is highly exothermic the heat produced will splash the acid and may cause burns.

Q 11. What is the cause of tooth decay?

Answer:  The bacteria present in the mouth act on sugar and food particles remaining in the mouth after eating to produce acids. The acid produced lowers the pH in the mouth to 5.5 and begins to attack the hard enamel and corrode it resulting in tooth decay.

Q 12. Plaster of Paris should be stored in a moisture-proof container. Explain why?

Answer:  Plaster of Paris (POP) or calcium sulphate with half a molecule of water per molecule of the salt (hemi-hydrate) is a hygroscopic substance. Should it absorb a little water from the surroundings, it evolves heat and quickly sets to a hard porous mass hence it should be stored in a moisture-proof container to keep it dry

Q.13 A milkman adds a very small amount of baking soda to fresh milk.

(a) Why does he shift the pH of the fresh milk from 6 to slightly alkaline?

(b) Why does this milk take a long time to set as curd?  

Ans: 
 (a) By adding small amount of baking soda, the milkman shifts the pH of the fresh milk from 6 to slightly alkaline so that he can keep it for longer time as the milk in alkaline condition, does not set curd easily.

(b) Since, this milk is slightly basic than the usual milk, acids produced due to bacterial actions in it are neutralized by the base. Therefore, it takes longer time to set as curd.    

Q.14.Give two important uses of washing soda and baking soda.

Ans: Uses of Washing Soda:

1. Sodium carbonate (washing soda) is used in glass, soap, and paper industries.

2. It is used in the manufacture of sodium compounds such as Borax.

Uses of Baking Soda:

1. Sodium hydrogen carbonate is also ingredient in antacids. Being alkaline, it neutralizes excess acid in the stomach and provides relief.2. It is also used in soda-acid fire extinguishers.

3. It is used as baking powder in confectionery items like cake, pastry etc.  

Q. 15. What will happen if a solution of sodium hydrocarbonate is heated? Give the equation of the reaction involved.

Ans. When a solution of sodium hydrocarbonate (sodium hydrogencarbonate) is heated, sodium carbonate and water are formed with the evolution of carbon dioxide gas.

2NaHCO₃    +        heat                  →    Na₂CO₃      +   H₂ O  + CO₂

Q. 16. Equal lengths of magnesium ribbons are taken in test tubes A and B. Hydrochloric acid (HCl) is added to test tube A, while acetic acid (CH₃COOH) is added to test tube B. In which test tube will the fizzing occur more vigorously and why?

Ans: The fizzing will occur strongly in test tube A, in which hydrochloric acid (HCl) is added. This is because HCl is a stronger acid than CH₃COOH and therefore produces hydrogen gas at a faster speed due to which fizzing occurs.

Q17. Plaster of Paris should be stored in a moisture-proof container. Explain why?

Ans. Plaster of Paris (POP) should be stored in a moisture-proof container because Plaster of Paris, a powdery mass, absorbs water (moisture) to form a hard solid known as gypsum.

Ca SO₄ . ½ H₂ O     +   1¹/₂ H₂ O     →   Ca SO₄ . 2 H₂O

Q 18 :Why should curd and sour substances not be kept in brass and copper vessels?

Ans:  Curd and other sour substances contain acids. Therefore, when they are kept in brass and copper vessels, the metal reacts with the acid to liberate hydrogen gas and harmful products, thereby spoiling the food.

Q19. Which gas is usually liberated when an acid reacts with a metal? Illustrate with an example. How will you test for the presence of this gas?

Ans: Hydrogen gas is usually liberated when an acid reacts with a metal.

Take few pieces of zinc granules and add 5 ml of dilute H₂SO₄. Shake it and pass the gas produced into a soap solution. The bubbles of the soap solution are formed. These soap bubbles contain hydrogen gas.                 
2H₂SO₄            +     Zn      →  Zn (SO₄)₂   +  2H₂  

We can test the evolved hydrogen gas by its burning with a pop sound when a candle is brought near the soap bubbles.

Q 20: Metal compound A reacts with dilute hydrochloric acid to produce effervescence. The gas evolved extinguishes a burning candle. Write a balanced chemical equation for the reaction if one of the compounds formed is calcium chloride.

  Ans:     CaCO₃  (s)   +    HCI(aq)    →   CaCI₂(aq) + CO₂   + H₂ O (I)

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