Biology · Oct / Nov 2021 · Paper 61 · Question 1

table drawn with a minimum of three columns and header line ;

column and row headings ;

six correct colours recorded ;

reducing sugars: Benedict’s (solution) ;

protein: biuret (solution) ;

starch: iodine (solution) ;

starch, protein and (reducing) sugars ;

substance: (reducing) sugars and evidence: positive test / orange, for substance in test-tube /liquid T;

idea that some of solution M might have got on to the outside of the tubing / idea of contamination / would give false results as solution M would be in the distilled water / AW ;

one precaution from the same row one hazard from:

as the hazard:

(damage to skin from) food testing

goggles / eye protection / gloves reagents / chemicals / solutions

/ liquids

hot water / flame / heat (for

stand up during practical work / use Benedict’s test)

of a water-bath / (heat-proof) gloves / use of tongs

;;

independent variable:

1

at least two different pH values ;

2,3 variables kept constant, two from: ;;

method:

4

use of an appropriate reagent to test for starch / reducing sugars ; 5

ref. to use of a spotting tile (with iodine) ;

6

ref. to heating Benedict’s solution ;

7

use of a buffer ;

8

method of maintaining a constant temperature described ;

9

repeat the whole investigation at least two times (three trials) ;