Give reasons for the following:
Pure substances have fixed melting or boiling points.

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Solution

Pure substance:
A pure material is a single type of matter that cannot be divided into different types of matter by physical processes.
A pure substance's particles are all the same.
It has a distinct composition and characteristics.
Since all particles in substance are the same, they will all melt or boil at the same temperture.
This is why pure substances have set melting and boiling points.

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Similar questions

Which of the following does not have a fixed melting point/boiling point ?

(a) gold (b) ethanol (c) air (d) oxygen

There are three substances X, Y and Z. The substance X does not have a fixed melting point or boiling point and it still shows the individual properties of its constituents. The substance Y is a pure substance which occurs in nature as such. The substance Y has a fixed melting point and boiling point but it cannot be broken down into simpler substances by any chemical means. The substance Z is also a pure substance whose properties are entirely different from those of its constituents. The substance Z can, however, be divided by electrolysis into two substances which belong to the same class of substances as Y.

(a) What type of substance could X be? Name one substance like X.

(b) What type of substance could Y be? Name one substance like Y.

(d) Which process involves absorption or release of an appreciable amount of energy: formation of substances X or formation of substance Z?

(e) Name the three groups into which all the substances like Y are divided on the basis of their properties.

Q. A pure substance has a very sharp melting and boiling point. True or false?

Give reason for the following :

Ionic compounds have usually high melting and boiling points.

Q. Give reasons for the following statements
Why covalent compounds
(i) are bad conductors of electricity.
(ii) have low melting and boiling points.

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Give reasons for the following: Pure substances have fixed melting or boiling points.

Give reasons for the following:
Pure substances have fixed melting or boiling points.