Metals and Non Metals Class 10 – Important Questions & Chapter Revision

Let’s discuss each topic of Metals and Non Metals Class 10 one-by-one

Differentiating between a metal and a non-metal

Metals and non-metals can be differentiated based on their physical and chemical properties. They can be differentiated based on their physical properties as:

Common reactions of metals and non metals

Reactions of metals and non metals have been dealt with in this chapter, and you should remember the products formed in each of them. You can put in the correct formula and valency for metals and non metals and create a chemical equation. Don’t forget to balance the equation!

Metal + oxygen —> metal oxide

Example, 2Cu+O2—>2CuO

Metal + water —> metal hydroxide

Now, different metals react with water at different rates.
K and Na react violently with cold water
Ca reacts with water, but less violently
Mg doesn’t react with cold water, but reacts with hot water
Al and Fe react only with steam

Metal + dilute acid —>salt + H2

Here, note that Hydrogen gas is not evolved when a metal reacts with nitric acid. It is because HNO3 is a strong oxidising agent. It oxidises the H2 produced to water and itself gets reduced to any of the nitrogen oxides (N2O, NO, NO2). Only Mg and Mn give H2 with dil. HNO3

Reaction of metals with salt solutions of other metals:

Metal A + salt solution of metal B Salt solution of A + Metal B
This is an example of a displacement reaction, where a more reactive metal A displaces metal B from its salt solution.
Here, if metal A is less reactive than metal B, no reaction will occur.
Now, how do we check if a metal is more reactive or less reactive than another? This is answered by studying the reactivity series.

The Reactivity Series

It is a list of metals arranged in the order of their decreasing activities.

For this chapter and even for future, it is very important for you to remember the correct order of this series.

Some students like to remember things by using mnemonics. So here is one for you!

“Please Stop Calling Me A cute Zebra. Instead, Like Her, Call Me Smart Goat.” This is what it means.

Potassium Sodium Calcium Magnesium Aluminium (Carbon) Zinc Iron Lead Hydrogen Copper Mercury Silver Gold

Reaction between Metals and Non Metals

We know that atoms of all elements (except hydrogen) need 8 electrons in their outermost shell for stability.

In a reaction between a metal and a non-metal, metals attain this stability by donating electrons, while non-metals do so by accepting electrons. Thus when they both combine, ionic bond is formed by the transfer of electrons.

Occurrence of Metals

Most metals are found in the earth’s crust in a combined form, and we have to extract them into their pure form, as they are very useful to us. This is again a very important topic, and you should read it thoroughly. This involves three parts – enrichment of ore, reduction to obtain metal, and refining/purification.

We will study this in 3 parts:

Extracting Metals Low in the Activity Series – These metals are very unreactive, and these metals can be extracted by heating alone. For example, Hg and Cu :

2HgS(s)+3O2(g)–>2HgO(s)+2SO2(g)

2HgO(s)—>2Hg(l)+O2(g)

Extracting Metals in the middle of the Activity Series – Metals present in this category are extracted by various processes. This topic is very important from exam point of view, so make sure you study this thoroughly. To revise this topic thoroughly, click on the card that you see on your screen.

Extracting Metals towards the top in the Activity Series – Highly reactive metals like sodium, calcium, aluminium etc are extracted from their molten chloride solution using electrolysis.

Let us take an example. If we want to extract sodium from molten sodium chloride solution, the reactions that take place are:

At cathode: Na++e–→Na

At anode: 2Cl–→Cl2+2e–

The metal is deposited at the cathode (the negatively charged electrode), whereas, chlorine is liberated at the anode (the positively charged electrode).

After extraction, metals have to be purified. This is done by the process of electrolytic refining. In this process, impure metal is made the anode and a thin strip of pure metal is made the cathode. A solution of the metal salt is used as an electrolyte. On passing the current through the electrolyte, the pure metal from the anode dissolves into the electrolyte. An equivalent amount of pure metal from the electrolyte is deposited on the cathode. The soluble impurities go into the solution, whereas, the insoluble impurities settle down at the bottom of the anode and are known as anode mud.

Corrosion

You know that iron or other metal articles get corroded in the presence of air and water. The rusting of iron can be prevented by painting, oiling, greasing, galvanising, chrome plating, anodising or making alloys. Alloying is a very good method of improving the properties of a metal, as we can get a substance with desired properties by this method. An alloy is a homogeneous mixture of two or more metals, or a metal and a nonmetal. If one of the metals is mercury, then the alloy is known as an amalgam.

Previous Year Questions

Let us now understand the weightage of this chapter. On analysing previous years’ papers, we can see that there is a higher probability of a 3 or 5 marks question being asked from this chapter.

3 marks

1. a) What are amphoteric oxides? Choose the amphoteric oxides from amongst the following oxides:

Na2O, ZnO, Al2O3, CO2, H2O

1. b) Why is it that non-metals do not displace hydrogen from dilute acids? [CBSE, 2008]
2. No chemical reaction takes place when granules of a solid, A, are mixed with the powder of another solid, B. However when the mixture is heated, a reaction takes place between its components. One of the products, C, is a metal and settles down in the molten state while the other product, D, floats over it. It was observed that the reaction is highly exothermic.
   1. Based on the given information make an assumption about A and B and write a chemical equation for the chemical reaction indicating the conditions of reaction, physical state of reactants and products and the thermal status of reaction.
   2. Mention any two types of reactions under which above chemical reaction can be classified.   [CBSE, 2010]

5 marks

1.  a) Distinguish between an ionic and covalent compound under the following properties:
   1. Strength of forces between constituent elements
   2. Solubility of compounds in water
   3. electrical conduction in substances

1. b) Explain how the following metals are obtained from their compounds by the reduction process :
   1. Metal M which is in the middle of the reactivity series.
   2. Metal N which is high up in the reactivity series.
   3. Give one example of each type. [CBSE, 2009]
2. What is meant by refining of a metals? Name the most widely used method of refining impure metals produced by various reduction processes. Describe with the help of a labelled diagram how this method may be used for refining of copper.’ [CBSE, 2010]

Let’s solve one of the questions: