How does it become possible to cause artificial rain by spraying silver iodide on the clouds? Q. 43 Gelatin which is a peptide is added in ice-creams. What can be its role? Ans. Emulsifying agent is added to emulsion to stabilise the emulsion. Emulsifying agent form a layer between suspended particles and the medium and hence stabilises the emulsion. Ice cream (emulsion) is stabilised by emulsifying agent like gelatin. Q. 44 What is collodion? Ans. 4\% solution of nitrocellulose in a mixture of alcohol and ether is called collodion. Q. 45 Why do we add alum to purify water? Ans. We add alum to purify water as alum coagulates the colloidal impurities present in water, so that these impurities get settle down and remove by decantation or filtration. Thus, water gets purified by adding alum to water.
As we know artificial rainfall occurs when oppositely charged clouds meets. Since, clouds are colloidal in nature and carry charge. Spray of silver iodide, an electrolyte from aeroplane results in coagulation of colloidal water particles leading to rain. Sometimes electrified sand is also used for this purpose.
Gelatin which is a peptide is added in ice-creams. What can be its role?
Emulsifying agent is added to emulsion to stabilise the emulsion. Emulsifying agent form a layer between suspended particles and the medium and hence stabilises the emulsion. Ice cream (emulsion) is stabilised by emulsifying agent like gelatin.
What is collodion?
$4 \%$ solution of nitrocellulose in a mixture of alcohol and ether is called collodion.
Why do we add alum to purify water?
We add alum to purify water as alum coagulates the colloidal impurities present in water, so that these impurities get settle down and remove by decantation or filtration. Thus, water gets purified by adding alum to water.
What happens when electric field is applied to colloidal solution?
When electric potential is applied to colloidal solution, the colloidal particles move towards one or other electrode. Positively charged particles move towards the cathode while negatively charged particles move towards the anode.
The movement of colloidal particles under an applied electric potential is called electrophoresis. When electrophoresis is prevented by some means, then the dispersion medium begins to move in an electric field. This phenomenon is termed as electroosmosis.