Draw a neat and labelled diagram of lactometer and answer the following questions:

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1

Draw a neat and labelled diagram of lactometer and answer the following questions:

  1. Why cannot it measure purity of milk?
  2. Why is its stem of very small area of cross-section?
  3. Why is the density of pure milk marked at the base of stem?
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  1. Purity of milk depends upon its fat content and not upon its density. This hydrometer cannot detect the fat content, and hence cannot tell purity of milk.
  2. Stem is made smaller so as to increase its sensitivity.
  3. It is, because, the density of pure milk is 1.04 g cm-3. Hence, hydrometer sinks less in it. On addition of water in the milk, the density of milk decreases and the hydrometer submerges more. Thus, density of milk is marked at the base of the stem.