The DAV Class 8 Science Book Solutions Pdf and DAV Class 8 Science Chapter 3 Question Answer – Metals and Non-metals are essential study tools for DAV public school students in Class 8.
DAV Class 8 Science Ch 3 Question Answer – Metals and Non-metals
DAV Class 8 Science Ch 3 Solutions – Metals and Non-metals
Something To Know
A. Fill in the blanks:
Question 1.
The property, due to which a metal piece can be hammered into thin sheet, is known as ________ .
Answer:
Malleability
Question 2.
Bronze is an alloy of ________ and ________.
Answer:
copper, tin
Question 3.
Gold is mixed with ________ and/or ________ to make it hard.
Answer:
copper, silver
Question 4
________ the only non-metal to have a natural lustre.
Answer:
graphite
Question 5
________ is a non-metal which catches fire in air.
Answer:
phosphorus
Question 6.
The only metal, which exists in the liquid state at room temperature is ________.
Answer:
mercury
B. Match the following:
| Column I | Column II |
| (1) Hardest substance | (a) Bromine |
| (2) Aluminium ore | (b) Graphite |
| (3) A non-metal, normally, existing in liquid state | (c) Bauxite |
| (4) A good electrical conductor | (d) Diamond |
| (5) A metalloid | (e) Arsenic |
Answer:
| Column I | Column II |
| (1) Hardest substance | (d) Diamond |
| (2) Aluminium ore | (c) Bauxite |
| (3) A non-metal, normally, existing in liquid state | (a) Bromine |
| (4) A good electrical conductor | (b) Graphite |
| (5) A metalloid | (e) Arsenic |
C. Tick (✓) the correct option:
Question 1.
The two most abundant metals, found in the earth’s crust, are-
(a) Aluminium and copper
(b) Aluminium and iron
(c) Iron and copper
(d) Iron and silver
Answer:
(b) Aluminium and iron
Question 2.
The metals, used in making the alloy ‘german silver’, are-
(a) Copper + zinc + tin
(b) Copper + zinc + nickel
(c) Copper + nickel + tin
(d) Copper + nickel + cobalt
Answer:
(b) Copper + zinc + nickel
Question 3.
When a metal reacts with oxygen, the resulting oxide of the metal-
(a) Is a neutral oxide
(b) Turns blue litmus red
(c) Is an acidic oxide
(d) Is a basic oxide
Answer:
(d) Is a basic oxide
Question 4.
Out of the metals, gold, silver, copper and aluminium, the one, that is most ductile is-
(a) Gold
(b) Silver
(c) Aluminium
(d) Copper
Answer:
(a) Gold
Question 5.
Two of the metals, that cannot be stored either in air, or under water, are-
(a) Sodium and magnesium
(b) Magnesium and calcium
(c) Calcium and potassium
(d) Potassium and sodium
Answer:
Potassium and sodium
D. Answer the following questions in brief:
Question 1.
Name (i) one metal and (ii) one non-metal which normally exist in the liquid state.
Answer:
Mercury (metal) and Bromine (non-metal) exist in liquid state.
Question 2.
State the fraction of gold present in an 18 carat gold piece.
Answer:
Fraction of gold in 18 carat gold = 18/24 = 3/4
Question 3.
State the property of copper wires that makes them useful for electrical fittings.
Answer:
Copper is a good conductor of electricity, and it is highly ductile. Moreover, copper is economical too. Due to this, copper is ideal for electrical fittings.
Question 4.
Define an alloy.
Answer:
A homogenous mixture of two or more metals or a metal and non-metal is called alloy.
Question 5.
List any two uses of non-metals.
Answer:
Following are the two uses of non-metals:
(i) Phosphorus is used for making matchsticks.
(ii) Diamond is used for cutting glass sheets.
E. Answer the following questions:
Question 1.
Write the balanced equations for the following reactions:
(a) Sodium reacts with oxygen
Answer:
4Na + O2 → 2Na20
(b) Aluminium reacts with dilute hydrochloric acid
Answer:
2Al + 6HCl → 2AlCl3 + 3H2
Question 2.
Why are gold and platinum suitable for making jewellery?
Answer:
Gold and platinum are highly malleable. They are noble metals; which means they do not lose lustre in the long run. Hence, gold and platinum are suitable for making jewellery.
Question 3.
‘Sodium and potassium is stored under kerosene’. Give reason.
Answer:
Sodium and potassium are highly reactive metals. They readily react with oxygen in air or in water. The reaction is highly exothermic. The reaction mixture quickly catches fire. Sodium and potassium are stored under kerosene to prevent their reaction with oxygen.
Question 4.
Why is bronze preferred over copper metal for making statues?
Answer:
Bronze is harder, stronger and more resistant to corrosion than copper. Hence, bronze is preferred over copper for making statues.
Value Based Question
The chemistry teacher, while teaching her students, explained to them the differences between ‘metals’ and ‘non-metals’. She told them that both of them react with the same gas; oxygen but their resulting oxides are ‘opposite’ in nature.
She then went on to say that, in a somewhat similar way, we could use our stay in the school either.
(a) To gain knowledge learn good manners and develop, and tone up, different skills or
(b) To indulge in idle gossip and other frivolous and irrelevant activities.
Question 1.
State two of the Values’ that the teacher conveyed to her students.
Answer:
Good manners and learning new skills
Question 2.
Give one example each of the reaction of a (i) metal, (ii) non-metal, with oxygen to explain the ‘opposite nature’ of the oxides formed in the two cases.
Answer:
Magnesium ribbon burns in air to produce dazzling white light. Magnesium oxide is formed in this reaction. Magnesium oxide is basic in nature.
Carbon burns in air to produce carbon dioxide. Carbon dioxide is acidic in nature. Acidic or basic nature of these oxides can be shown by brining wet litmus papers near them. Magnesium oxide will turn the red litmus blue. Carbon dioxide will turn the blue litmus red.
Question 3.
Let the students form two teams: M (metals) and N (non-metals); let the two teams form ‘pairs’ to explain the differences between their properties.
Answer:
Do it yourself
Something To Do
Question 1.
Find out the names of places in India where mines of gold, copper and iron are located. Also, write the names of the places where major steel plants are located.
Answer:
- Gold Mine: Kolar
- Copper Mines: Jharsugora
- Iron mines: Jamshedpur
- Steel Plants: Bokaro, Jamshedpur, Bhilai
Question 2.
The study of extracting metals from their ore is called metallurgy. Centuries ago, India was far ahead in metallurgy. Refer to books in library and find out the history of metallurgy in India.
Answer:
Do it yourself
Question 3.
Make a list of five articles used at home and school, which are made up of metals or alloys. Write their composition in a tabular form.
Answer:
Do it yourself
DAV Class 8 Science Chapter 3 Solutions – Metals and Non-metals Important Questions and Answers
I. Fill in the blanks:
1. Most of the metals have very ________ boiling point.
Answer:
High
2. ________ is the only metal which is present in liquid state at room temperature.
Answer:
Mercury
3. ________ and ________ are normally used for making electrical wires.
Answer:
Aluminium, copper
4. For making steel, ________ is added to iron.
Answer:
Carbon
5. ________ is an alloy of iron, chromium and nickel.
Answer:
Stainless steel
II. Tick the correct answer:
Question 1.
Which of the following is the hardest substance?
(a) Iron
(b) Platinum
(c) Diamond
(d) Charcoal
Answer:
(c) Diamond
Question 2.
Which of the following is the most reactive metal?
(a) Potassium
(b) Sodium
(c) Zinc
(d) Calcium
Answer:
(a) Potassium
Question 3.
Which of the following is a noble metal?
(a) Gold
(b) Silver
(c) Platinum
(d) All of these
Answer:
(d) All of these
Question 4.
Oxide of which of the following is basic in nature?
(a) Iron
(b) Carbon
(c) Phosphorus
(d) Sulphur
Answer:
(a) Iron
Question 5.
Which gas is evolved when a metal reacts with dilute acid?
(a) Oxygen
(b) Carbon dioxide
(c) Hydrogen
(d) Nitrogen
Answer:
(c) Hydrogen
III. Answer the following questions:
Question 1.
Write a brief note on occurrence of metals.
Answer:
Metals are present in the earth’s crust in abundance. Aluminium is the most abundant metal and iron is the next. Highly reactive metals are found in the form of their oxides, sulphides and carbonates, e.g. sodium, potassium, aluminium and zinc. Less reactive metals are found in their elemental or native state, e.g. gold, silver and platinum.
Question 2.
What is a mineral?
Answer:
A naturally occurring inorganic substance found deep under the surface of the earth is called mineral.
Question 3.
What is an ore?
Answer:
A mineral from which one or more metals can be profitably extracted is called ore.
Question 4.
What do you understand by malleability?
Answer:
Metals can be beaten into thin sheets. This property of metals is called malleability. Non-metals are non-malleable.
Question 5.
What do you understand by ductility?
Answer:
Metals can be drawn into thin wires. This property of metals is called ductility. Non-metals are non-ductile.
Question 6.
What are metalloids? Give some examples of metalloids.
Answer:
Some elements show properties of metals as well as non-metals. These Eire called metalloids. Silicon, germanium, arsenic, etc. are examples of metalloid.
Question 7.
How does a metal react with oxygen? Explain with suitable example.
Answer:
Metals react with oxygen to form metallic oxides. Metallic oxides are basic in nature:
Metal + Oxygen → Metal Oxide
When magnesium ribbon is burnt, it reacts with oxygen to make magnesium oxide.
2Mg + O2 → 2MgO
(Magnesium) (Oxygen) → (Magnesium Oxide)
IV. Projects:
Question 1.
Show the comparison between metals and non-metals in a tabular form. Stick to physical properties only, while showing this comparison.
Answer:
Do it yourself
Question 2.
Ask your teacher to demonstrate the reaction of sodium with water.
Answer:
Do it yourself
Question 3.
Make a flow chart to show different steps of metallurgy.
Answer:
Do it yourself