The control variable in any experiment is designed in order to apply the same steps of the experiment but with no change happens in the observations.
In this experiment, the student tries to know the effect of solubility of different water-soluble salts (NaCl, CaCl2 and KCO3) on the melting point of the solution. All these salts dissolve in water and give some effect on the melting point except for the sand as the sand doesn't dissolve in water.
It's a pic of 4 ..genetic engineering.. as the selected part of a specific DNA is used for some research !
Answer:
Sound travels fastest through solids. This is because molecules in a solid medium are much closer together than those in a liquid or gas, allowing sound waves to travel more quickly through it. In fact, sound waves travel over 17 times faster through steel than through air.
