She then tried the method suggested in activity 7, to recover the salt. she found, however, that she could recover only a small part of the salt that she had taken. what could have gone wrong?
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Take a mixture of sand and salt. How will we separate these? We already saw that handpicking would not be a practical method for separating these.
Keep this mixture in a beaker and add some water to this. Leave the beaker aside for some time. Do you see the sand settling down at the bottom? The sand can be separated by decantation or filtration. What does the decanted liquid contain? Do you think this water contains the salt which was there in the mixture at the beginning?
Now, we need to separate salt and water from the decanted liquid. Transfer this liquid to a kettle and close its lid. Heat the kettle for some time. Do you notice steam coming out from the spout of the kettle?
Take a metal plate with some ice on it. Hold the plate just above the spout of the kettle as shown in Fig. 5.13. What do you observe? Let all the water in the kettle boil off.
When the steam comes in contact with the metal plate cooled with ice, it condenses and forms liquid water. The water drops that you observed falling from the plate, were due to condensation of steam. The process of conversion of water vapour into its liquid form is called condensation.
Did you ever see water drops condensed under a plate that has been used to cover a vessel containing milk that has just been boiled?
After all the water has evaporated, what is left behind in the kettle?
We have thus, separated salt, sand and water using processes of decantation, filtration, evaporation and condensation.
Paheli faced a problem while recovering salt mixed with sand. She has mixed a packet of salt in a small
Fig. 1 Evaporation and condensation
amount of sand. She then tried the method suggested in Activity 7, to recover the salt. She found, however, that she could recover only a small part of the salt that she had taken. What could have gone wrong?
Keep this mixture in a beaker and add some water to this. Leave the beaker aside for some time. Do you see the sand settling down at the bottom? The sand can be separated by decantation or filtration. What does the decanted liquid contain? Do you think this water contains the salt which was there in the mixture at the beginning?
Now, we need to separate salt and water from the decanted liquid. Transfer this liquid to a kettle and close its lid. Heat the kettle for some time. Do you notice steam coming out from the spout of the kettle?
Take a metal plate with some ice on it. Hold the plate just above the spout of the kettle as shown in Fig. 5.13. What do you observe? Let all the water in the kettle boil off.
When the steam comes in contact with the metal plate cooled with ice, it condenses and forms liquid water. The water drops that you observed falling from the plate, were due to condensation of steam. The process of conversion of water vapour into its liquid form is called condensation.
Did you ever see water drops condensed under a plate that has been used to cover a vessel containing milk that has just been boiled?
After all the water has evaporated, what is left behind in the kettle?
We have thus, separated salt, sand and water using processes of decantation, filtration, evaporation and condensation.
Paheli faced a problem while recovering salt mixed with sand. She has mixed a packet of salt in a small
Fig. 1 Evaporation and condensation
amount of sand. She then tried the method suggested in Activity 7, to recover the salt. She found, however, that she could recover only a small part of the salt that she had taken. What could have gone wrong?
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Answer:
too much of salt
Explanation:
asas there is too much of salt it will not dissolve in the given amount of water so it is difficult to separate the sand and the salt
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