Class 11th|Chemistry Viva-Voce Question Answers.

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Q1. Define melting point.

Ans. Melting point is the temperature at which solid and liquid states of a substance co-exist or it is the temperature at which a solid on heating changes into its liquid form.

Q2. What is a sharp melting point?

Ans. The melting is termed sharp when a solid is completely melted within a range of 1°C.

Q3. What is the effect of impurity on the melting point of a solid ?

Ans. The melting point of the solid is lowered by the presence of impurity.

Q4. What is the criteria of purity of a solid?

Ans. It is pure if its melting point is sharp and does not change on purification of the solid.

Q5. Do crystalline substances have sharp melting points?

Ans. Yes, generally they have sharp melting points.

Q6. Why electrovalent compounds have generally high melting points?

Ans. The electrovalent compounds are made up of positive and negative ions.
There is a strong force of attraction between the oppositely charged ions,so a lot of energy is requried to break this force of attraction and melt the eelectrovalent compound. Due to this, electrovalent compounds have high melting points.

Q7.Why covalent compounds have usually low melting points?

Ans. Covalent compounds are made up of electrically neutral molecules. So, the force of attraction between the molecules of a covalent compound is very weak only a small amount of heat energy is required to break these weak molecular forces, due to which covalent compounds have low melting points.

Q8. What happens during melting of a solid?

Ans. During melting, the molecules of the substances move more freely and the substance changes into its liquid state.

Q9. What do you understand by the term sharp melting point?

Ans. A substance is said to possess a sharp melting point if it changes from solid to liquid state completely within a range of 1°C.

Q10.What is the importance of melting point?

Ans. Every pure substance has a fixed melting point. Impurities depress the melting point of a substance.

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