18. (i) Classify Brass and Diamond as element and mixture
(ii) How is a chemical change different from a physical change?
(iii) Identify the heterogeneous mixture from the following in soda water, soap solution and
brass.
(iv) Suggest a suitable technique for the following
(a) Mercury and water (b) Coloured components from Blue ink
Answers
Answer:
Explanation:
Diamond is an element whereas brass is a mixture. Diamond is a molecular form of Carbon which makes it an element as it can exist at room temperature and the pressure in the various forms or allotropes. Where brass is made up of mixing copper and zinc together and have properties of both the alloys.
In a physical change the appearance or form of the matter changes but the kind of matter in the substance does not. However in a chemical change, the kind of matter changes and at least one new substance with new properties is formed. The distinction between physical and chemical change is not clear cut.
Solution : (A) Soap solution is a heterogeneous mixture while the rest are of homogeneous nature. ... For example, a colloidal solution of starch in water (Starch acts as dispersed phase and water as the dispersion medium)
Blue or black dye can be separated from ink by the process of evaporation. Ink is a colloidal solution and a heterogeneous mixture of dye and water. Heating leads to evaporation of water. This leaves behind dye in watch-glass.
diamond is a element and brass is a mixture