What are amphoteric oxides? Give an example. Write balanced chemical equations to justify your answer.

Give reason:

Metals like sodium and potassium are stored under oil.

A student, took four metal P, Q, R and S and earned out different experiments to study the properties of metals. Some of the observations were: 

•  All metals could not be cut with knife except metal R.
•  Metal P combined with oxygen to form an oxide ${\mathrm{M}}_2{\mathrm{O}}_3$ which reacted with both acids and bases. 
•  Reaction with water. 

P — Did not react either with cold or hot water but reacted with steam

Q — Reacted with hot water and the metal started floating  

R — Reacted violently with cold water.  

S — Did not react with water at all.

Based on the above observations answer the following:

Out of the given metals, the one which needs to be stored used kerosene is-

A student, took four metal P, Q, R and S and earned out different experiments to study the properties of metals. Some of the observations were: 

•  All metals could not be cut with knife except metal R.
•  Metal P combined with oxygen to form an oxide ${\mathrm{M}}_2{\mathrm{O}}_3$ which reacted with both acids and bases. 
•  Reaction with water. 

P — Did not react either with cold or hot water but reacted with steam

Q — Reacted with hot water and the metal started floating  

R — Reacted violently with cold water.  

S — Did not react with water at all.

Based on the above observations answer the following:

Out of the given metals, the metal Q is:

A student, took four metal P, Q, R and S and earned out different experiments to study the properties of metals. Some of the observations were: 

•  All metals could not be cut with knife except metal R.
•  Metal P combined with oxygen to form an oxide ${\mathrm{M}}_2{\mathrm{O}}_3$ which reacted with both acids and bases. 
•  Reaction with water. 

P — Did not react either with cold or hot water but reacted with steam

Q — Reacted with hot water and the metal started floating  

R — Reacted violently with cold water.  

S — Did not react with water at all.

Based on the above observations answer the following:

Metal which forms amphoteric oxides is:

A student, took four metal P, Q, R and S and earned out different experiments to study the properties of metals. Some of the observations were: 

•  All metals could not be cut with knife except metal R.
•  Metal P combined with oxygen to form an oxide ${\mathrm{M}}_2{\mathrm{O}}_3$ which reacted with both acids and bases. 
•  Reaction with water. 

P — Did not react either with cold or hot water but reacted with steam

Q — Reacted with hot water and the metal started floating  

R — Reacted violently with cold water.  

S — Did not react with water at all.

Based on the above observations answer the following:

The increasing order of the reactivity of four metals is: