Samacheer Kalvi 8th Science Unit 9 Book Back Answers:

Samacheer Kalvi 8th Standard New Science Book Back 1 Mark and 2 Mark Question & Answers PDF uploaded and available below. Class 8 New Syllabus 2021 to 2022 Book Back Question & Answer available for both English and Tamil Mediums. Class 8th Science Book Unit 9 – Matter Around Us Answers/Solutions are provided on this page. 8th Std Science Book consists of 23 units, All Science Book Back One, and Two Mark Solutions are given below.

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Samacheer Kalvi 8th Science Book Back Solutions PDF:

8th Science Subject 1 Mark and 2 Mark Solutions PDF available below. Click the Download option to download the book back 1 Mark & 2 Mark questions and answers. Take the printout and use it for exam purposes. Samacheer Kalvi 8th Science Unit 9 Answers are given below.

Science Book Back Answers

Unit 9 – Matter Around Us

I. Choose the best answer.

1. The liquid metal used in thermometers is –
(a) Copper
(b) Mercury
(c) Silver
(d) Gold
Answer:
(b) Mercury

2. The pictorial symbol for water given by the alchemists was

3. Which one of the following element name is not derived from planet?
a) Plutonium b) Neptunium
c) Uranium d) Mercury

4. Symbol of mercury is
a) Ag b) Hg c) Au d) Pb

5. A form of non-metal that has high ductility is
a) nitrogen b) oxygen
c) chlorine d) carbon

6. The property which allows the metals to be hammered into their sheets is
___________
a) ductility b) malleability
c) conductivity d) shining strength

7. The non-metal which conducts electric current is
a) carbon b) oxygen
c) aluminium d) sulphur

8. Pencil lead contains
a) graphite b) diamond
c) aluminium d) sulphur

9. Identify the state of matter based on the arrangement of the molecules.

a) A – Gas, B – Solid, C – Liquid
b) A – Liquid, B – Solid, C – Gas
c) A – Gas, B – Solid, C – Liquid
d) A – Liquid, B – Gas, C – Solid

II. Fill in the blanks.

1. The element which possesses the character of both metals and non metals are called __________
2. The symbol of tungsten is __________
3. Melting point of most metal is __________ than non-metal.
4. Water contains _________ and _________ element.
5 ____________ is used as semiconductor.

III. Match the following:

1. Question

1.	Iron	(A)	For making wires
2.	Copper	(B)	Sewing needle
3.	Tungsten	(C)	As a fuel for ignition in rocket.
4.	Boron	(D)	Making the filament of a bulb

Answer:

1. B
2. A
3. D
4. C

2. Question

1.	Atom	(A)	building block of matter
2.	Element	(B)	atoms of different kinds
3.	Compound	(C)	atoms of the same kind
4.	Molecule	(D)	smallest unit of a substance

(a) 1 – A, 2 – C, 3 – B, 4 – D
(b) 1 – C,2 – A, 3 – B, 4 – D
(c) 1 – D, 2 – C, 3 – B, 4 – A
(d) 1 – B, 2 – C, 3 – A, 4 – D
Answer:

1. A
2. C
3. B
4. D

IV. Answer very briefly.

1. What is ductility?
Answer:
Metals can be drawn into thin wires. This property of metals is called ductility.
Example : Copper wires.

2. Write the constituent elements and their symbols for the following compounds

1. Carbon monoxide
2. Washing soda

Answer:

Compound	Symbols	Constituent elements
Carbon monoxide	(CO)	Carbon and oxygen
Washing soda	(Na2CO3)	Sodium, carbon and oxygen

3. Write the symbols for these elements

1. Oxygen
2. Gold
3. Calcium
4. Cadmium
5. Iron

Answer:

S.No	Element	Symbols
(i)	Oxygen	O
(ii)	Gold	Au
(iii)	Calcium	Ca
(iv)	Cadmium	Cd
(v)	Iron	Fe

 

4. Which non – metal is essential for our life and all living beings inhale it during breathing?
Answer:
Oxygen is essential for our life and all living beings inhale it during breathing.

5. Why are bells made of metals?
Answer:
On being hit, metals produce a typical sound. They are said to be sonorous. This property is being made used in making bells.

6. What does a chemical symbol represent?
Answer:
A chemical symbol is a shorthand method of representing an element.

Symbol of an element signifies:

1. Name of the element.
2. One atom of the element for example,
3. The symbol O stands for the element of oxygen.
4. One atom of oxygen.

7. Give two examples for metalloids.
Answer:
Boron and silicon.

8. Mention any three compounds that exist in liquid state.
Answer:

1. Water
2. Hydro chloric Acid
3. Nitric Acid

9. Write three properties of metalloids.
Answer:
Properties of metalloids:
Metalloids are all solid at room temperature.

1. They can form alloys with other metals
2. Some metalloids, such as silicon and germanium, can act as electrical conductors under the specific conditions, thus they are called semiconductors.
3. Silicon for example appears lustrous, but is not malleable nor ductile (it is brittle – a characteristic of some non – metals). It is a much poorer conductor of heat and electricity than the metals

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