Question

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.

1. What type of substance could X be ? Name one substance like X.
2. What type of substance could Y be ? Name one substance like Y.
3. What type of substance could Z be ? Name one substance like Z.
4. Which process involves absorption or release of an appreciable amount of energy : formation of substance X or formation of substance Z ?
5. Name the three groups into which all the substances like Y are divided on the basis of their properties.

Answer 1

1. 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.
2. 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.
3. 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.
4. Formation of Z (a compound) involves absorption or release of an appreciable amount of energy.
5. 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.