8th Science Guide Unit 9 Matter Around Us

8th Std Science Guide Lesson 9 Matter | English Medium 

8th Science Guide Unit 9 Matter Around Us book back answers. 8th Standard Science Guide English Medium Book Back Answers. 8th Science Samacheer kalvi guide Tamil Medium and English Medium Book Back and additional questions and answers. 8th Text Book download pdf. 8th std All Subject Guide. 

• 8th Science Guide (All Units)- Book Back Answers – TM & EM – Click Here

8th Science Guide Unit 9 Matter Around Us

I. Choose the best answer

1. Matter is composed of

1. atoms
2. molecules
3. ions
4. all of the above

Ans: all of the above

2. The liquid metal used in thermometers is

1. Copper
2. Mercury
3. Silver
4. Gold

Ans: Mercury

3. The Pictorial symbol for water given by the alchemists was

Matter Book Back Solution

Ans: C

4. Which one of the element name not derived from planet?

1. Plutonium
2. Neptunium
3. Uranium
4. Mercury

Ans: Mercury

5. Symbol of Mercury is

1. Ag
2. Hg
3. Au
4. Pb

Ans:  Hg          

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

1. nitrogen
2. oxygen
3. chlorine
4. carbon

Ans: carbon

7. Which one of metal possess low tensile strength?

1. Silver
2. Copper
3. Zinc
4. Aluminium

Ans: Zinc

8. The property which allows metals to be hammered into their sheets is ___________

1. ductility
2. malleability
3. conductivity
4. tensile strength

Ans: malleability

9. The non-metal which conduct current is

1. carbon
2. oxygen
3. aluminium
4. sulphur

Ans: carbon

10. Pencil lead contains

1. graphite
2. diamond
3. aluminium
4. sulphur

Ans: graphite

II. Fill in the blanks.

1. The element which possess character of both metals and non metals are called __________ Ans : Metalloids

2. The symbol of Tungsten __________ Ans : W
3. Melting point of most metal is __________ than non-metal. Ans : higher
4. Water contains ________ and ________ element.Ans : Hydrogen and Oxygen
5. ________ is the used in semiconductor industry Ans : Silicon and germanium

III. True or False

1. Metals are generally good conductors of electricity, but not good conductors of heat. Ans : False

Cu. St : Metals are generally good conductors of electricity, and not good conductors of heat.

2. Gallium metal is in solid state at or just above room temperature. Ans : False

Cu. St : Gallium metal is in Liquld state at or just above room temperature.

3. Compounds can be made up of one atom. Ans: False

Cu. St : Compounds cannot be made up of one atom.

4. Coal can be drawn into wires. Ans: False

Cu. St : Coal cannot be drawn into wires.

5. Zinc is highly ductile in nature. Ans: False

Cu. St : Copper is highly ductile in nature

IV. Match the following:

1. Iron – For making wires
2. Copper – Sewing needle
3. Tungsten – As a fuel for ignition in rocket.
4. Boron – Making the filament of a bulb

Ans : 1 – b, 2 – d, 3 – c, 4 – a

2.

1. Atom – building block of matter
2. Element – atoms of different kinds
3. Compound – atoms of the same kind
4. Molecule – smallest unit of substance

Ans : 1 – D, 2 – C, 3 – B, 4 – A

Molecule —- D. smallest unit of a substance

• 1 – A, 2 – C, 3 – B, 4 – D
• 1 – C, 2 – A, 3 – B, 4 – D
• 1 – D, 2 – C, 3 – B, 4 – A
• 1 – B, 2 – C, 3 – A, 4 – D

Ans : 1 – D, 2 – C, 3 – B, 4 – A

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

1. A – gas, B – solid, C – liquid
2. A – Liquid, B – solid, C – Gas
3. A – gas, B – solid, C – liquid
4. A – Liquid, B – Gas, C – Solid

Ans : A – gas, B – solid, C – liquid

V. Very Short Answer Questions:

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.

1. a) Carbon monoxide

(CO) – Carbon and oxygen

1. b) Washing soda

Na2CO3) – Sodium, carbon and oxygen

3. Write the symbols for these elements

• Oxygen – O
• Gold – Au
• Calcium – Ca
• Cadmium – Cd
• Iron – Fe

4. Name two soft metals that can be cut with a knife.

Sodium, Potassium

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

Oxygen

6. Why are bells made of metals?

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

7. What does a chemical symbol represent?

• A chemical symbol represents name of the element, one atom of the element for example, The symbol O stands for the element of oxygen, One atom of oxygen.

8. Give two examples for metalloids.

• Boron and silicon.

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

• Water, Hydro chloric Acid, Nitric Acid

10. Write three properties of metalloids.

• Metalloids can form alloys with other metals
• Some metalloids, such as silicon and germanium, can act as electrical conductors under the specific conditions, thus they are called semiconductors.
• They physical properties of metalloids tend to be metallic, but their
• chemical properties tend to non-metallic.

V. Short Answer Questions:

1. Can you store pickle in an aluminium utensil? Explain.

No, we cannot store the lemon pickle in aluminium utensil because aluminium is a metal and lemon is acidic. The acids react with metals to give hydrogen which would spoil the food and makes it unfit to use.

2. Tabulate four points of difference between metals and non – metals.

Property	Metal	Non – metal
Physical state at room temperature	Usually solid (occasionally liquid)	Solid, liquid or gas.
Malleability	Good	Poor – usually soft or brittle.
Ductility	Good	Poor – usually soft or brittle.

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

• The cooking utensils are made up of aluminium and brass because they are good conductors of heat.
• Aluminium will form a layer of protective oxide that prevents further reaction.
• Aluminium is also relatively cheap and that is why it is used widely in making utensils.

4. Define a Alchemy.

• Alchemy was form of chemistry studied in the middle age, which was concerned with trying to discover ways to change ordinary metals into gold.

5. Name the elements for following symbols.

• Na – Sodium
• W – Tungsten
• Ba – Barium
• Al – Aluminium
• U – Uranium.

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

Non – metals	Symbols
Sulphur	S
Carbon	c
Oxygen	0
Hydrogen	H
Helium	He
Nitrogen	N

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.
• Slaked lime – White washing of walls
• Lime stone – Preparation of chalk pieces

8. Mention the metals that are used in jewellery.

• Silver and gold are used for making jewels and in decorative purposes

9. Mention the uses for the following compounds.

• 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. Give Reason out:

1. a) Aluminium foils are used to wrap food items.

Aluminium is malleable, soft and does not react with food items, so it is used to wrap food items.

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

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

1. c) A doctor prescribed a tablet to a patient suffering from iron deficiency the tablet does not look like iron.

It does not like iron, iron tablets does not contains iron metals, rather it contains iron salts like ferrous sulphate, ferrous citrate etc.

1. d) Mercury is used in thermometers.

Mercury is used in thermometers and barometers because of its high density and uniform expansion at different temperature.

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

• Wires cannot be drawn from wood or stone. Because wood is bad conductor of electricity and it does not assist the properties which metals have such as malleability.