(i) High energy of activation is needed.
(ii) BIood being a colloidal solution gets coagulated by alum (an electrolyte).
(iii) Dust particles along with water suspended in air scatter blue light which reaches our eyes.
Detailed Answer
(i) This happens initially as increase in temperature provides high energy of activation required in chemical adsorption.
(ii) As blood is a colloidal solution, on applying the moist alum coagulation of blood takes place. This helps in stopping the bleeding.
(iii) Because of scattering and dispersion of light. The light gets incident on the atmospheric particles scattering the sunlight. Due to larger scattering of blue colour, sky appears blue in colour.
