Metals and non-metals

Q1) Which is denser Sodium or Zinc ?

Ans:

Sodium

Q2) Which has a higher melting point a thin tungsten wire or a thick iron nail?

Ans:

A thin tungsten wire.

Q3) What will not react with alkali , a copper sheet or an aluminum sheet.

Ans:

A Copper sheet.

Q4) what is more reactive – Sodium or Lead?

Ans:

Sodium

Q5) Which is magnetic – Iron wire or magnesium foil?

Ans:

Iron wire.

Q6) Which is harder – a piece of Copper or diamond?

Ans:

Diamond.

Q7) Explain malleability with an example.

Ans:

Most metals can be hammered into thin sheets or foils without breaking. This property is known as malleability.

Gold, Silver, Lead and Aluminum are high malleable metals.

Q8) Why are electric wire made from Copper.

Ans:

Electric wire are made from Copper because it is cheap   and good conductor of electricity.

Q9) why are cooking utensils made from metals?

Ans:

Cooking utensils are made from metals because they are good conductors of heat.

Q10) Why is Sodium stored in paraffin wax ?

Ans:

Sodium is stored in paraffin wax because Sodium is highly reactive metal.

Q11) why are Helium and Neon are called Nobel gases?

Ans:

Helium and Neon are called Nobel gases because they do not react with other elements.

Q12) What are alloys? Give one example.

Ans:

An alloy is obtained by mixing two or more metals and a non-metal.

Ex: Brass.

Q13) state any four physical properties of metals

Ans:

1- strong

2- hard

3- high melting and boiling points

4- high density

5- malleable

6- ductile

7- good conductor of heat and electricity

8- lustrous

Q14) How rust is formed?

Ans:

Iron reacts with Oxygen in the presence of water or moisture to form iron oxide. Iron oxide is commonly known as rust.

Iron + Oxygen -----Water-----à Iron Oxide

4Fe + 3O2 ---------H2O---------à 2Fe2O3

Q15) Explain the reaction between Sodium and Water

Ans:

Sodium metal reacts vigorously with water giving out a lot of heat to form a colourless solution of sodium hydroxide and Hydrogen gas.

Q16) What is a displacement reaction? Explain with an example.

Ans:

The reactivity series gives the information about displacement reactions in which one element displaces the other because it is more reactive.

Displacement reaction take place when a metallic salt solution react with another metal.

Ex: the Copper sulphate solution reacts with iron. Iron is more reactive than Copper, that is why iron displace Copper from Copper Sulphate and forms Iron Sulphate .

Iron + Copper Sulphate ---------à Copper + Iron Sulphate

Fe + CuSo4 ------------à Cu + FeSo4

Q17) Mention any two ways of preventing iron from rusting ?

Ans:

1) Painting:

Surface of iron can be coated with paint to keep air and water away from the metal surface.

However, rusting takes place quickly on iron surface if the paint is even slightly damaged . If the paint peels off , the portion  should be painted again.

2) coating with oil or grease

Bicycle chains, door hinges and car engines which can not be painted are coated by a layer of oil or grease.

Q18) Write a short note on the metals in the human body.

Ans:

Certain metals are essential to living beings and are present in minute quantities in them.

Ex:

1) Sodium and Potassium help in transmitting electrical signals to and from the brain through nerves .

2) Iron ( Fe) is a component of hemoglobin in the red blood cells.

3) Calcium ( Ca) salts are needed in the formation of bones and teeth.

Q19) How do non-metals differ from metals in their physical properties.

Ans:

Metals	non-metals
Lustrous	Non lustrous
Hard	Brittle
High melting and boiling  points	Low melting and boiling points
Malleable	Not malleable
Ductile	Not ductile
Strong	Not strong
High density	Low density
Good conductors of heat and electricity	Bad  conductors of heat and electricity

Q20) List the uses of silicon and phosphorous .

Ans:

Silicon is used for making electronics components like transistors, integrated circuits, microprocessors and chips used in computers.

It is used in the manufacture of cutting and grinding tools for industries.

Phosphorous is used in the making of fertilizers .

 Red phosphorous is used to make matchstick heads.

It is also used in fireworks, since phosphorous is poisonous it is used for preparing chemical  that kill pests like rats.