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ScienceClass 8CBSE

Fill in the blanks to complete the following paragraph. The name of the product formed in the reaction of sulphur and is sulphur dioxide gas. When sulphur dioxide is dissolved in , sulphurous acid is formed. The sulphurous acid turns litmus paper to Generally oxides of are acidic in nature. After completing the paragraph write two questions which you can raise on the basis of this information.

The name of the product formed in the reaction of sulphur and Oxygenis sulphur dioxide gas. When sulphur dioxide is dissolved in water, sulphurous acid is formed. The sulphurous acid turns bluelitmus paper to red. Generally oxides of nonmetalsare acidic in nature. After completing the paragraph write two questions which you can raise on the basis of this information. When Sulphur reacts with oxygen which gas is produced? What happen when sulphur dioxide is dissolved in water ?

ScienceClass 8CBSE

Some of the following statements are incorrect. Find the incorrect statements and correct them. (a) The property of metals by virtue of which they can be drawn into wires is called ductility. (b) Metals are good conductor of electricity but poor conductor of heat. (c) Articles made of metals produce ringing sound when struck hard. (d) Oxides of non-metals and metals are acidic in nature. (e) A less reactive metal replaces a more reactive metal from its salt solution in water.

Statement b) d) and e) are wrong statements b) Metals are good conductors of electricity as well as Oxides of non-metals are acidic in nature and oxides of metals are basic in A more reactive metal replaces a less reactive metal from its salt solution in

ScienceClass 8CBSE

Match the substances in Column A with their applications given in Column B. Column A (Substance) Column B (Application) (a) oxygen (i) for making crackers (b) copper (ii) for disinfecting water (c) sulphur (iii) all living beings inhale during breathing (d) iron (iv) for making electric wires (e) chlorine (v) for making rails

Column A (Substance) Column B (Application) (a) oxygen (iii) all living beings inhale during breathing (b) copper (iv) for making electric wires (c) sulphur (i) for making crackers (d) iron (v) for making rails (e) chlorine (ii) for disinfecting water

ScienceClass 8CBSE

A doctor prescribed a tablet to a patient suffering from iron deficiency. The tablet does not look like iron. Explain

Tablets are made from salts of iron hence it does not look like iron.

ScienceClass 8CBSE

Paheli prepared a blue coloured solution of copper sulphate in beaker A and placed an iron nail in it. Boojho prepared a yellowish green solution of ferrous sulphate in beaker B and placed a copper wire in it. What changes will they observe in the two beakers after an hour?

In beaker A, a reddish brown layer of copper will deposit on the iron nail and the blue coloured solution will become yellowish green. On the other hand, no change is observed in beaker B.

ScienceClass 8CBSE

If in Fig. 4.1 iron nail is replaced by a wooden stick, will the bulb glow or not? Justify your answer

If iron nail is replaced by a wooden stick bulb will not glow as wood is a bad conductor of electricity.

ScienceClass 8CBSE

Paheli bought a statue made of copper. To her surprise it acquired a dull green coating after a couple of months. Explain the reason.

Green coating on copper statue is the mixture of CU(OH)2 and CUCO3 which are formed due to reaction of moisture and copper.

ScienceClass 8CBSE

Which of the following metals can displace the other two metals from their salt solutions?

Zinc

ScienceClass 8CBSE

Which liquid metal is used for making thermometers?

Mercury

ScienceClass 8CBSE

Why are bells made of metals?

Metals show sonorous property hence they are used in making bells.

ScienceClass 8CBSE

Zinc sulphate forms a colourless solution in water. Will you observe any colour on adding copper turning in it?

There will no change as displacement reaction will not take place.

ScienceClass 8CBSE

A purple coloured non-metal forms a brown solution in alcohol which is applied on wounds as an antiseptic. Name the nonmetal.

Iodine

ScienceClass 8CBSE

Which non-metal is used to disinfect water?

Chlorine

ScienceClass 8CBSE

Name two major non-metals which are present in fertilisers and enhance the growth of plants.

nitrogen (ii) phosphorus

ScienceClass 8CBSE

Which non-metal is essential for our life and all living beings inhale it during breathing?

Oxygen

ScienceClass 8CBSE

Name two soft metals which can be cut with a knife.

sodium (ii) potassium

ScienceClass 8CBSE

Which of the following property is not responsible for copper to be used as electrical conduction wires? (a) ductility (b) colour (c) good conductor of electricity it is solid

Answer is (b) colour

ScienceClass 8CBSE

Generally metallic oxides are basic and non-metallic oxides are acidic in nature. Solution of which of the following oxides in water will change the colour of blue litmus to red? (a) sulphur dioxide (b) magnesium oxide (c) iron oxide copper oxide

Soln: Answer is (a) sulphur dioxide Explanation: Sulphur forms Sulphur-di-oxide which is acidic in nature and it will convert blue litmus to red.

ScienceClass 8CBSE

Which of the following non-metals reacts and catches fire on exposure to air? (a) phosphorus (b) nitrogen (c) sulphur (d) hydrogen

Answer is (a) phosphorus

ScienceClass 8CBSE

The metal which produces hydrogen gas on reaction with dilute hydrochloric acid as well as sodium hydroxide solution is (a) copper (b) iron (c) aluminium sodium

Soln: Answer is (c) aluminium Explanation: Aluminium reacts with dilute HCl as well as NaOH to produce Hydrogen Gas.

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