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.

(c) What type of substance could Z be? Name one substance like Z.

(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.

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Solution

(a) Substance X does not have a fixed melting or boiling point. Moreover, it shows the properties of its constituents. So, it must be a mixture. Sugar solution in water is a substance like X.
(b) Substance Y has a fixed melting or boiling point but it cannot be split into simpler substances by chemical processes. Hence, it must be an element. Hydrogen is a substance like Y.
(c) Substance Z is also a pure substance whose properties are entirely different from those of its constituents. Hence, it must be a compound. Sugar is a substance like Z.
(d) Formation of Z (a compound) involves absorption or release of an appreciable amount of energy.
(e) The three groups are metals, non-metals and metalloids. All the substances like Y are divided into these groups on the basis of their properties.

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Q. The substance X normally exists in a physical state which can flow easily but does not fill its vessel completely. It also turns anhydrous copper sulphate blue. When substance X is cooled excessively, it changes into a substance Y which has a fixed shape as well as a fixed volume. If, however, the substance X is heated strongly, it changes into a substance Z which has neither a fixed shape nor a fixed volume.

(a) Name the substances (i) X (ii) Y and (iii) Z.
(b) What is the process of conversion of X into Y known as ?
(c) At which temperature X gets converted into Y ?
(d) What is the process of conversion of X into Z known as ?
(e) At which temperature X gets converted into Z ?

The substance X normally exists in a physical state which can flow easily but does not fill its vessel completely. It also turns anhydrous copper sulphate blue. When substance X is cooled excessively, it changes into a substance Y which has a fixed shape as well as a fixed volume, If, however, the substance X is heated strongly, it changes into a substance Z which has neither a fixed shape nor a fixed volume.

(a) Name the substance. (i) X (ii) Y and (iii) Z.

(b) What is the process of conversion of X into Y known as?

(d) What is the process of conversion of X into Z known as?

(e) At which temperature X gets converted into Z?

Q. There is a large group of materials P which can be divided into three groups Q, R and S on the basis of their properties. The substances belonging to group Q can be solids, liquids or gases. The solids belonging to group Q are usually electrical insulators. Most of the substances of group R are solids which are good conductors of electricity. The substances belonging to group S are neither insulators like Q not good conductors like R. The properties of S are intermediate between those of Q and R.

(a) What could the group of materials P be ?
(b) Name the substances Q. Give two examples of such substances.
(c) Name the substances R. Write two examples of such substances.
(d) Name the substances S. Give two examples of such substances.
(e) Out of Q, R and S, which substances are malleable and ductile ?

Q. Burning characterstics of three substances are given below:What type of combustion does X, Y and Z undergo?

Study the information given below:

1) Some substances are formed when two or more elements combined together chemically.
2) Properties of these substances are different from their respective constituents.
3) These substances cannot be broken down into their respective constituents by physical methods.

Which of the following substance has the properties listed above?

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