Here we will discuss chemical properties of metals class 8 notes which includes reactions with oxygen, with water, with acids, with bases and displacement reactions of metals.
After reading this post you will be able to answer all the questions asked in the examination.
Chemical reactions of metals class 8 Notes
We must go through chemical reactions of metals if we want to know their chemical properties. Chemical reactions of metals depend on reactivity of metals. Here we will go through following chemical reactions of metals –
- Reaction with oxygen
- Reaction with water
- Reaction with acids
- Reaction with base
- Displacement reaction of metals
Reaction of Metals with oxygen
Metals react with oxygen to form metal oxides and metal oxides are basic in nature.
Metal + Oxygen → Metal oxide
Reactivity of different metals with oxygen is different so they react with oxygen differently.
i. Metals like sodium and potassium combine very rapidly and vigorously with oxygen
`4Na + O_2 →2Na_2O`
`4K+ O_2 →2K_2O`
ii. When magnesium reacts with oxygen on burning with a white dazzling flame and form powdered magnesium oxide
`2Mg+ O_2 →2MgO`
iii. Zinc and iron react with oxygen at very high temperature, but they do not burn.
`2Zn+ O_2 →2ZnO`
`3Fe+ 2O_2 →Fe_3O_4`
iv.Copper reacts with oxygen on heating long time and a layer of black copper oxide is formed on its surface.
`2Cu+ O_2 →2CuO`
Copper is less reactive.
v. Metals like chromium and manganese form acidic oxides
`4 Cr + 3O_2→ 2Cr_2O_3`
vi. Aluminium, tin and zinc reacts with oxygen and form amphoteric oxides.
`2Al + 3O_2 →2Al_2O_3`
vii. Silver and gold do not react with oxygen even at high temperature.
Reaction of Metals with water
Different metals react with water at different temperatures. Metals react with water to produce metal hydroxide and hydrogen gas but the intensity of the reaction is different.
Metal + Water →Metal Hydroxide + Hydrogen gas
i.Metals such as Sodium and potassium react violently with water at room temperature or even with cold water. This reaction is so vigorous that it catches fire.
`2Na+ 2H_2O →2NaOH + H_2↑ + heat`
`2K+ 2H_2O →2KOH + H_2↑ + heat`
ii.Calcium reacts with water less violently, so less heat is liberated.
`Ca + 2H_2O →Ca(OH)_2 + H_2↑`
Calcium starts floating in water because the bubbles of hydrogen gas formed stick to the surface of calcium.
iii. Magnesium reacts with hot water and produces magnesium hydroxide.
` Mg + 2H_2O →Mg (OH)_2 + H_2↑`
iv. Metals like aluminium, zinc and iron only react with steam.
`3Fe+ 4H_2O → Fe_3O_4 + 4H_2↑`
`2Al+ 2H_2O →Al_2O_3 + 3H_2↑`
`Zn + 2H_2O →Mg (OH)_2 + H_2↑`
v. Copper, gold and silver, lead do not react with water in any condition.
Reaction of Metals with acids
Metals above hydrogen in reactivity series react with dilute acids but metals below hydrogen in the series do not react with dilute acids.
Metal reacts with acids produce metal salts and hydrogen gas.
Metal + dilute acid →Metal salt + Hydrogen
i.Sodium, potassium and lithium reacts with dilute acids violently form salts and hydrogen gas.
`2Na + 2HCl →2NaCl+ H_2`
`2K + 2HCl →2NaCl+ H_2`
`2Na + H2SO_4 → Na_2SO_4 + H_2`
ii. Magnesium , zinc react with acids to produce relevant salt and H2 gas.
`Mg+ 2HCl →MgCl_2 + H_2`
`Mg+ H_2SO_4 →MgSO_4 + H_2`
`Zn + 2HCl →ZnCl_2 + H_2`
`Zn + H2SO_4 →ZnSO_4 + H_2`
iii. Copper, silver and gold do not react with dilute acids.
`Cu + 2HCl →No reaction`
iv. Copper reacts with oxy acids like `HNO_3`, `H_2SO_4`
`Cu+ 2HNO_3 →Cu(NO_3)_2 + 2NO +4H_2O`
In this reaction, Hydrogen gas is not liberated.
v. Aluminium and iron reacts with acids very fast and produce relevant salts.
`2Al + 6HCl →2AlCl_3 + 3H_2`
`Fe + 2HCl →FeCl_2 + H_2`
Hydrogen gas is not evolved when a metal reacts with nitric acid.
Reaction of Metal with Bases
Metals react with base to form sat and hydrogen gas.
Metal + Base →Metal salt + Hydrogen
i. When aluminium is heated with sodium hydroxide solution, then sodium aluminate and hydrogen gas are formed.
`2Al + 2NaOH + 2H_2O → 2NaAlO_2 + 3H_2`
ii.Sodium zincate and hydrogen gas are formed when sodium hydroxide is heated with zinc.
`Zn + 2NaOH Na_2ZnO_2 + H_2`
Reaction of Metal with metal salts
These reactions are also called displacement reactions of metals. More reactive metals displace less reactive metals from their oxide, chloride or sulphate salts solutions.
Metal A + Salt solution of Metal B →salt solution of Metal A + Metal B
i.Reaction of zinc with copper sulphate solution : When a strip of zinc is dipped in the blue solution of copper sulphate, the blue colour of copper sulphate disappears due to formation of colouless zinc sulphate and zinc strip become red brown due to deposition of copper on it.
`CuSO_4 + Zn → ZnSO_4 + Cu`
ii. Reaction of iron with copper sulphate solution : Iron displaces copper from it solution and form iron sulphate.
`Fe + CuSO_4 → FeSO_4 + Cu`
iii. Reaction of copper with silver nitrate : Copper displaces silver from silver nitrate and form blue copper sulphate and silver metal.
`Cu + 2AgNO_3 → Cu(NO_3)_2 +2Ag`
Important Questions Based on Chemical Properties of Metals
1.What is the general reaction when a metal reacts with oxygen?
Ans – Metal reacts with oxygen to form metal oxide that is basic in nature.
2.Name two metals that react with oxygen very vigorously.
Ans – Sodium and potassium are highly reactive metals and react vigorously with oxygen.
3.Write the balanced chemical equation for the reaction of magnesium with oxygen.
Ans – `2Mg + O2 →2MgO`
4.What products are fomed when zinc and iron react with oxygen?
Ans – Zinc oxide, ferric oxide
5.What happens when copper reacts with oxygen upon heating?
Ans – A black layer of copper oxide is formed on its surface.
6.Which metal forms acidic oxide when reacts with oxygen?
Ans – Chromium
7.What type of oxides are formed when aluminium and zinc react with oxygen?
Ans- Amphoteric oxides are formed when Al and Zn react with oxygen. These oxides have both acidic and basic properties.
8.Do silver and gold react with oxygen?
Ans – No, these metals are non reactive so they don’t react with oxygen.
9.Why does calcium start floating when it reacts with water?
Ans – Calcium starts floating because the bubbles of hydrogen gas stick to the surface of calcium.
10.Which metals react with steam ?
Ans- Zinc, aluminium, iron react with steam.
11.Do copper, silver and gold react with water?
Ans- No, they don’t react with water.
12.What are the products when metals react with acids?
Ans- Metals react with acid to form metal salts and hydrogen gas.
13.Write the balanced equation for the reaction of magnesium with HCl.
Ans- `Mg + 2HCl → MgCl_2 + H_2`
14.Name the metals that do not react with dilute acids.
Ans – Copper, silver and gold do not react with dilute acids.
15.What happens when sodium hydroxide reacts with aluminium?
Ans – Sodium illuminate and hydrogen gas are formed.
Quiz On Chemical Properties of Metals
FAQs
1.What is the reaction of metals with oxygen class 8?
Ans- Metals reacts with oxygen to form metal oxides.
2.What happens when sodium reacts with oxygen?
Ans – Reaction between sodium and oxygen is very vigorous and sodium oxide is formed.
3.What is the balanced chemical equation of sodium reacts with oxygen?
Ans – `4Na + O_2 →2Na_2O`
4.Name the product formed when sodium reacts with oxygen.
Ans- Sodium oxide
5.When magnesium reacts with oxygen nature of the bond formed is?
Ans – When magnesium reacts with oxygen , an ionic bond is formed.
6.What product is formed when magnesium reacts with oxygen?
Ans- Magnesium oxide
7.What happens when magnesium reacts with oxygen in terms of electrons?
Ans- Magnesium donate 2 electrons to form `Mg^2+` and oxygen gains 2 electrons to form`O^2-`
Transfer of electrons takes place between magnesium and oxygen.
8.Which compound is formed when copper reacts with oxygen?
Ans- Copper oxide
9.When copper reacts with oxygen what would you observe?
Ans- We observe that a black layer is formed on the surface of copper which is copper oxide.
10.What happens when silver reacts with oxygen?
Ans- Silver does not react with oxygen.