What differences would be observed between the mixture of salt and sand in the \[250\] -mL beaker and the same materials after the water was added?

Hint :Sand is not soluble in water but salt is. Also, the amount of water added will decide the amount of salt soluble in the water. Thus, the amount of salt in the prepared slurry after adding water will vary depending upon the amount of water added.

Complete Step By Step Answer:
Now, first of all, the mixture of sand and salt has been prepared and it is poured in a \[250\] ml beaker. In the prepared mixture, you may or may not see salt mixed in the sand. They may or may not be distinguishable depending upon the amount of salt you add to the sand.
After the water is added, the sand will make a slurry with water as it is insoluble in it. The salt will dissolve in water after a certain amount of time. After the salt is dissolved, the only thing that will remain will be the slurry.
Also, the amount of salt dissolved in the water will depend on the amount of water you add to the mixture. If the amount of water added is not sufficient enough for the salt to dissolve, the salt will remain as it is.
The look of slurry made by sand and water will vary with the amount of water too. If a lot of water is added, the slurry will be thin and if an only a small amount of water is added, the slurry will be thick.

Note :
Here, the amount of water added will decide the amount of salt being dissolved. The look of the slurry made by sand and water will also depend on the amount of water added to the mixture. Thus, water added to the mixture plays an important role.