A school food laboratory uses the apparatus in Fig. 1 to test an unknown drink. The student adds Benedict's solution to the drink in a test tube and warms t...
Question 1 Report
A school food laboratory uses the apparatus in Fig. 1 to test an unknown drink. The student adds Benedict's solution to the drink in a test tube and warms the tube in a hot water bath. A second tube containing distilled water and Benedict's solution is treated in the same way. The unknown drink changes from blue to brick-red.
(a) Name the food substance identified by Benedict's test. [1]
(b) State the result expected in the distilled-water tube. [1]
(c) Explain why the tubes are heated in a water bath rather than directly in a flame. [2]
(d) Complete the conclusion: the unknown drink contains a reducing ______. [1]
Answer Details
(a) Benedict's test identifies a reducing sugar, such as glucose. [1]
(b) The distilled-water control contains no reducing sugar, so Benedict's solution remains blue. [1]
(c) Heating causes the Benedict's reaction and colour change when reducing sugar is present. A water bath heats the tube safely and evenly, avoiding direct overheating by a flame. [2]
(d) The unknown drink contains a reducing sugar. The brick-red result supports this conclusion. [1]
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