VIII-EM-Matter around us

MATTER AROUND US

TEXTBOOK EXERCISE

 

I.  Choose the best answer.

1. The liquid metal used in thermometers is

a) copper

b) mercury

c) silver

d) gold

Ans:b) mercury

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

Ans:c) ▽

3. Which one of the following element name is not derived from planet?

a) Plutonium

b) Neptunium

c) Uranium

d) Mercury

Ans:c) Uranium

 4. Symbol of mercury is

a) Ag

b) Hg

c) Au

d) Pb

Ans:b) Hg

5.  A form of non-metal which has high ductility is

a) nitrogen

b) oxygen

c) chlorine 

d) carbon

Ans: 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

Ans: b) malleability

7. The non-metal which conducts electric current is

a) carbon

b) oxygen

c) aluminium

d)  Sulphur

Ans: a) carbon

8. Pencil lead contains

a) graphite

b) diamond

c) aluminium

d)  Sulphur

Ans: a) graphite

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 - Liquid,   C - Solid

d) A - Liquid,     B - Gas,   C – Solid

Ans:a) A - Gas,         B - Solid, C - Liquid

 

II.  Fill in the blanks.

1. The element which possesses the character of both metals and non- metals are called __________.

Ans : metalloids

2. The symbol of tungsten is __________.

Ans : W

3.  Melting point of most metal is __________ than non-metal.

Ans : greater

4.  Water contains _________ and _________ element.

Ans : Hydrogen, Oxygen

5 ____________ is used as semiconductor.

Ans : Silicon

III.  Match the following.

a. 

Ans:

Iron	Sewing needle
Copper	For making wires
Tungsten	Making the filament of a bulb
Boron	As a fuel ignition in rocket.

 

b.Ans:

Atom	Smallest unit of a substance
Element	Building block of matter
Compound	Atoms of different kinds
Molecule	More than one atom

 

IV.   Answer very briefly.

1. What is ductility?

       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.

a) Carbon monoxide   b) Washing soda

Compounds	Elements	Symbols
a) Carbon monoxide	Carbon	C
	Oxygen	O
b) Washing soda	Sodium	Na
	Carbon	C
	Oxygen	O

3. Write the symbols for the following elements.

a) Oxygen b) Gold c) Calcium d) Cadmium e) Iron

        

Elements	Sybmobl
a) Oxygen	O
b) Gold	Au
c) calcium	Ca
d) cadmium	Cd
e) Iron	Fe

4. Which non-metal is essential for our life and all living beings?

       Oxygen

5. Why are bells made of metals?

       On being hit, metals produce a typical sound. Hence, they are said to be sonorous. This property is being made used in making temple bells.

6.  What does a chemical symbol represent?

       A chemical symbol is a shorthand method of representing the name of an element.

7. Give two examples for metalloids.

       Boron and Silicon.

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

       Water, Hydrochloric acid and Nitric acid.

9. Write three properties of metalloids.

       a. Metalloids are all solid at room temperature.

b. They can form alloys with other metals

c. Some metalloids, such as silicon and germanium, can act as electrical conductors under the specific conditions, thus they are called semiconductors.

V.   Answer briefly.

1. Can you store pickle in an aluminium utensil? Give reason.

       Pickle cannot be stored in aluminium utensil. Because acids in pickle react with aluminium and liberates hydrogen gas. This will lead to the spoiling of pickle.

2. Tabulate the differences between metals and non-metals.

Property	Metal	Non-metal
Conductivity	Good	Very poor
Malleability	Good	Poor (usually soft or brittle)
Ductility	Good	Poor (usually soft or brittle)
Melting point	Usually high	Usually low
Boiling point	Usually high	Usually low
Density	Usually high	Usually low

 

3. Why are utensils made up of aluminium and brass?

       The utensils are made up of aluminium and brass because they are good conductors of heat. These metal utensils are generally tinned from inside to prevent any reaction between such metal and foodstuff.

4. Define Alchemy.

       The alchemists try to change less valuable metal into gold. The process was called Alchemy.

5. Name the elements with the following symbols.

a) Na  b) W  c) Ba  d) Al  e) U

 

Symbols	Elements
a) Na	Sodium
b) W	Tungsten
c) Ba	Barium
d) Al	Aluminium
e) U	Uranium

6. Name six common non-metals and write their symbols.

 

Name of the non-metals	Symbols
i) Nitrogen	N
ii) Oxygen	O
iii) Carbon	C
iv) Sulphur	S
v) Phosphorus	P
vi) Chlorine	Cl

7. Mention any four compounds and their uses.

Water	For drinking and as solvent.
Table salt	Essential component of our daily diet, preservative for meat and fish.
Sugar	Preparation of sweets, toffees and fruit juices.
Baking soda	Fire extinguisher, preparation of baking powder and preparation of cakes and bread.

 

8. Name the metals that are used in jewellery.

Gold, Silver, Platinum and Copper

9. Mention the uses of the following compounds.

a) Baking soda  b) Bleaching powder  c)  Quick lime

Compounds	Uses
Baking soda	Fire extinguisher, preparation of baking powder and preparation of cakes and bread.
Bleaching powder	As bleaching agent, disinfectant and sterilisation of drinking water.
Quick lime	Manufacture of cement and glass

 

 

VI. Given reason.

1. Give reasons for the following.

(a)  Aluminum foils are used to wrap food items.

Ans : Because aluminium being a soft malleable metal it can be beaten into sheets and form thin wrapping sheets. Moreover it does not react with food items.

(b)  Immersion rods for heating liquids are made up of metallic substances.

Ans : Metals are good conductors of heat and electricity. So, immersion rods made up of metallic substances.

(c)  Sodium and potassium are stored in kerosene.

Ans :Because kerosene contains  no coater  and protects these metals from being exposed to any moisture in the air that would cause these metals to react potentially and violently.

(d) Mercury is used in thermometers.

Ans : Mercury is the only one metal in liquid state at room temperature. It is used in thermometers because it has high co efficient of expansion. Hence the slightest change in temperature can be noted.

2. Why wires cannot be drawn from materials such as stone or wood?

Ans : Wires are used in the conduction of electricity. Stone and wood are non- conductors of electricity. So, wires cannot be drawn from materials such as stone or wood.

Share This:

Whatsapp Whatsapp