Properties of Substances – Maharashtra Board Class 8 Solutions for General Science (English Medium)
MathematicsGeneral ScienceMaharashtra Board Solutions
Solution 1:
- Melting point: The temperature at which the state of a substance changes from solid to liquid is called the melting point of the substance.
- Boiling point: The temperature at which a substance boils is called its boiling point.
- Distillation: Distillation is a process in which a liquid is first heated to its boiling point, and its vapour is cooled to obtain the liquid again.
Solution 2:
Distillation:
Solution 3.a:
A condenser has two taps which acts as an inlet and an outlet to allow the circulation of cold water around the inner tube.
Solution 3.b:
A condenser has two taps which acts as an inlet and an outlet to allow the circulation of cold water around the inner tube.
Solution 4:
| ‘A’ | ‘B’ |
| a. Melting point | 4. Change of state from solid to liquid. |
| b. Boiling point | 3. Change of state of a liquid into a gas. |
| c. Fractional distillation | 2. Obtaining diesel from crude oil. |
| d. Distillation | 1. Separating common salt and water from their mixture. |
Solution 5.a:
Take some water in a beaker. Introduce a thermometer into the water in such a way that the bulb of the thermometer is completely immersed in water. Insert a stirrer into the water. Arrange the apparatus as shown in the figure.
Heat the water with a burner. Keep on stirring the water. After some time, the temperature starts rising till it reaches 100°C. At this temperature, water starts boiling and is converted into steam. The temperature remains constant till a large quantity of water is converted into steam. The temperature so recorded is the boiling point of water.
Solution 5.b:
After lighting a candle, the wax melts into liquid as it has a low melting point. The melted wax also burns on the wick producing carbon dioxide and water. Therefore, when a candle burns, it changes into the solid, liquid and gaseous states.
Solution 5.c:
Yes. Distillation is a process of separating a solid substance from its solution. Example: Seawater is a mixture of salt and water. During distillation, water gets distilled out and the salt crystals remain in the distillation flask.