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Class 8 > science chapter-4 > Flashcards

science chapter-4 Flashcards

1
Q

How many elements are known?

A

116

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2
Q

How many elements are metals

?

A

89

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3
Q

Number of elements that are Non-metals

A

18

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4
Q

What are Noble Metals?

A

Metals which react rarely are called Noble Metals for example gold and silver

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5
Q

What are ores?

A

The minerals from which metals can be extracted profitably and conveniently are called ores

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6
Q

Define Metallurgy?

A

It is science of extracting of metals from their respective ores and then refining them

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7
Q

Define Ductility?

A

The property of metals due to which they can be drawn into wires is called Ductility

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8
Q

Define malleability

A

The property of metals due to which they can be drawn into sheets is called Malleability

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9
Q

Name physical properties of metals?

A

Physical state ,Hardness ,Melting or Boiling point ,Malleability ,Ductility ,Conductivity ,Density ,Lustre ,Sonority

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10
Q

Metal + Oxide =

A

Metaloxide

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11
Q

2Mg + O2 =

A

2MgO

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12
Q

Metal + Oxygen

A

Metal oxide + hydrogen !

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13
Q

Metal + Oxygen

A

Metal oxide + hydrogen !

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14
Q

Metal + dilute salt

A

Metal salt + hydrogen !

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15
Q

What is Displacement reaction?

A

Displacement reaction is a chemical reaction in which a more reactive element displaces a less reactive element from its compound.

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16
Q

Cu + FeSo4

A

No reaction

17
Q

Mg + CuSO4

A

MgSo4 + Cu

18
Q

Define Corrosion

A

The formation of layer of undesirable compounds on the surface of metals due to exposure to oxygen and moisture is called Corrosion

19
Q

Bronze is an alloy of

A

Copper and Tin

20
Q

How can we prevent corrosion?

A

Corrosion of metals can be prevented if the metal surface is not allowed to come in contact with moist air

21
Q

Non-Metals define

A

Non-metals are those elements that accepts electrons to form negatively charged ions called anions

22
Q

Write examples of free form of carbon

A

Graphite diamond and coal

23
Q

What are Alloys?

A

Sometimes a metal or non metal is added to metal to improve its properties. The final substance obtained is called an Alloy.

24
Q

Why is alloy used?

A

Alloy is used to increase hardness , resistance to corrosion and for changing physical and chemical properties.

25
Q

Define Elements

A

A pure substance that consist of only one kind of atoms

26
Q

Define Elements

A

A pure substance that consist of only one kind of atoms

Class 8 (3 decks)

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