Long Answers - Materials: Metals and Non-Metals, Science, Class 8 Class 8 Notes | EduRev

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Class 8 : Long Answers - Materials: Metals and Non-Metals, Science, Class 8 Class 8 Notes | EduRev

The document Long Answers - Materials: Metals and Non-Metals, Science, Class 8 Class 8 Notes | EduRev is a part of the Class 8 Course Class 8 Science by VP Classes.
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LONG ANSWER TYPE QUESTIONS
 

Q. 1. Explain the reaction of non-metals with oxygen with the help of an activity.
Ans.
Take some amount of powdered sulphur in a deflagrating spoon and heat it. As soon as sulphur  starts burning, introduce the spoon into a gas jar or glass tumbler with a lid to ensure that the gas produced does not escape. Add some amount of water into the tumbler and quickly replace the lid. Shake well. Test the solution with red and blue litmus papers.
We observe that solution changes the colour of blue litmus into red. It shows that nonmetallic oxides are acidic in nature.

Long Answers - Materials: Metals and Non-Metals, Science, Class 8 Class 8 Notes | EduRev  Long Answers - Materials: Metals and Non-Metals, Science, Class 8 Class 8 Notes | EduRev


Q. 2. Name the acids and bases which you use in laboratory. Identify the metals or non-metals present in them which form oxides with oxygen.
Ans.
Metals and Non-metals in Acids and Bases

S. No.

Name of the Base

Metal

Name of the Acid

Non-metal

1.

Calcium hydroxide

Calcium

Sulphuric acid

Sulphur

2.

Magnesium hydroxide

Magnesium

Hydrochloric acid

Chlorine

3.

Potassium hydroxide

Potassium

Nitric acid

Nitrogen

4.

Sodium hydroxide

Sodium

Carbonic acid

Carbon and Oxygen

5.

Zinc hydroxide

Zinc

Sulphurous acid

Sulphur.

 


 Q. 3. Explain the reaction of metals and non-metals with acids with the help of an activity.
Ans.
Take samples of metals and non‑metals in separate test tubes and label them A, B, C, D, E and F . With the help of a dropper add 5 ml of dilute hydrochloric acid to each test tube one by one. Observe the reaction carefully. If no reaction occurs in the cold solution, warm the test tube gently. Bring a burning matchstick near the mouth of each test tube.
Repeat the same activity using dilute sulphuric acid in place of dilute hydrochloric acid. Record your observation in a table:

Table: Reaction of Metals and Non-metals with Acids

Test

tube

Label

Metal/

Non-metal

Reaction with Dilute Hydrochloric Acid

Reaction with Dilute Sulphuric Acid

Room

Temperature

Warm

Room

Temperature

Warm

A

Magnesium

(ribbon)

Reacts to give

hydrogen

Rapid

reaction

Reacts to give

hydrogen

Rapid

reaction

B

Aluminium (foil)

Reacts to give

hydrogen

Rapid

Reacts to give

hydrogen

Rapid

C

Iron (filings)

Reacts to give

hydrogen

Rapid

Reacts to give

hydrogen

Rapid

D

Copper (peeled flexible wire)

No reaction at all

No reaction

No reaction

Reacts to give hydrogen

E

Charcoal

(Powder)

No reaction at all

No reaction

No reaction

No reaction

F

Sulphur

(Powder)

Does not react

at all

No reaction

No reaction

No reaction

 


Q. 4. Write the uses of metals and non-metals.
Ans.
Uses of Metals:
(i) Metals are used in making machinery.
(ii) Metals are used in making automobiles, aeroplanes and trains.
(iii) They are used in making satellites.
(iv) They are used in making industrial gadgets, cooking utensils and water boilers.

Uses of non-metals:
(i) Non‑metal like oxygen is essential for our life which all living beings inhale during breathing.
(ii) They are used in fertilizers.
(iii) They are used in medicines as antiseptic.
(iv) They are used in crackers.


Q. 5. Write the differences between metals and non-metals on the basis of their physical properties.
Ans.

Metals Non-metals
1. Metals are good conductors of heat and electricity
2. Metals are malleable and ductile
3. Metals are lustrous and can be polished.
4. Metals are solid, except mercury
5. Metals have generally high melting points and boiling points
1. Non-metals are poor conductors of heat and electricity
2. Non-metals are neither malleable nor
ductile.
3. Non-metals are usually non-lustrous and cannot be polished.
4. Non-metals can exist in all states.
5. Non-metals generally have low melting points and boiling points.
 


Q. 6. Compare the metals and non-metals on the basis of their chemical properties.
Ans.

Metals Non-metals
1. Metals react with oxygen to produce
oxides which are alkaline in nature.
2. Metals react with water differently to
produce oxides and hydroxide.
3. Metals react with acid to produce hydrogen gas.
4. More reactive metals displace the less
reactive metals from their compounds
in an aqueous solution.
1. Non-metals react with oxygen to produce oxides which are basic in nature.
2. Non metals do not react with water.
3. Non-metals most of times do not react with acids.
4. Non-metals do not show any such action

 

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