$A$ group of students took an old shoe box and covered it with black paper from all sides. They fixed a source of light (a torch) at one end of the box by making a hole in it and made another hole on the other side to view the light. They placed a milk sample contained in a beaker/tumbler in the box as shown in the figure. They were amazed to see that the milk taken in the tumbler was illuminated. They tried the same activity by taking a salt solution but found that light simply passed through it.
$(a)$ Explain why the milk sample was illuminated. Name the phenomenon involved.
$(b)$ Same results were not observed with a salt solution. Explain.
$(c)$ Can you suggest two more solutions which would show the same effect as shown by the milk solution?
$(a)$ Explain why the milk sample was illuminated. Name the phenomenon involved.
$(b)$ Same results were not observed with a salt solution. Explain.
$(c)$ Can you suggest two more solutions which would show the same effect as shown by the milk solution?
(N/A) Milk is a colloid. Colloidal particles are large enough to scatter a beam of light passing through them,which makes the path of light visible. This phenomenon is known as the Tyndall effect.
$(b)$ $A$ salt solution is a true solution. The particles in a true solution are extremely small (less than $1 \ nm$ in diameter) and are unable to scatter the beam of light passing through them. Therefore,the path of light is not visible in a salt solution.
$(c)$ Two other examples of colloidal solutions that show the Tyndall effect are starch solution and soap solution.
$(b)$ $A$ salt solution is a true solution. The particles in a true solution are extremely small (less than $1 \ nm$ in diameter) and are unable to scatter the beam of light passing through them. Therefore,the path of light is not visible in a salt solution.
$(c)$ Two other examples of colloidal solutions that show the Tyndall effect are starch solution and soap solution.
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$(i)$ Small pieces of metal in the engine oil of a car.
$(ii)$ Fine mud particles suspended in water.
$(iii)$ Oil from water.
$(iv)$ Sodium chloride from its solution in water.
$(v)$ Camphor from salt.
$(vi)$ Wheat grains from husk.
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$(i)$ Water boils to form steam.
$(ii)$ Burning of paper.
$(iii)$ An almirah gets rusted.
$(iv)$ Making a fruit salad with raw fruits.
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$(b)$ $A$ solution is always a liquid. Comment.
$(c)$ Can a solution be heterogeneous?
$(a)$ Under which category of mixtures will you classify alloys and why?
$(b)$ $A$ solution is always a liquid. Comment.
$(c)$ Can a solution be heterogeneous?
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