Sweeter than sugar

UNDERSTANDING YOUR FOOD<br /> the ultimate educational resource<br /> TEACHER NOTES<br /> <br /> teachers’ notes S5.1<br /> S5. Sweeter than sugar<br /> Pupils do practical activities to compare the ‘densities’ of drinks<br /> containing artifical sweeteners and sugar.<br /> Answers to questions on Pupil activity<br /> Sheet S5. Task 1<br /> The accurate measurement of volumes is very important.<br /> 1. aspartame, saccharin and acesulphame K are the most common<br /> 2. this will vary depending on the tablets<br /> 3. ~3.0 g<br /> 4. ~22.0 g<br /> 5. The artificial sweeteners weigh considerably less than equivalent<br /> volumesof sugar. These volumes have thesamesweetness. The<br /> artificial sweeteners areconsiderably sweeter than sugar and are<br /> therefore present in relatively tiny amounts.<br /> 6. ~9.9 g<br /> 7. ~10.5 g<br /> 8. The sugar solution weighs more than an equal volume of sweetener<br /> solution. It has a greaterdensity. The sweetener present has a much<br /> smaller mass than the sugar.<br /> Task 2<br /> 1. Typical ingredients (e.g. Sainsbury’s own brand lemonade):<br /> KS4<br /> science and food technology<br /> Timing - 40 - 60 minutes<br /> Two pupil activity sheets S5<br /> accompany this activity.<br /> Requirements<br /> • artificial sweetener tablets<br /> • granulated artificial sweetener<br /> • ordinary table sugar (sucrose)<br /> • balance, accurate to 0.1 g<br /> • teaspoons<br /> • distilled water<br /> • 10 cm<br /> 3graduated pipettes<br /> • teat pipettes<br /> • small beakers or similar<br /> • sample of ‘ordinary’<br /> lemonade labelled A<br /> • sample of ‘diet’ lemonade (be sure<br /> that it does not contain sugar)<br /> labelled B<br /> • the empty bottles/containers from<br /> the lemonade or the labels from<br /> the containers or copies of these<br /> • apparatus for testing for<br /> reducing sugar/glucose,<br /> i.e. heating equipment, water bath,<br /> Benedict’s solution, test tubes or<br /> boiling tubes, test tube holder, test<br /> tube rack, safety goggles, Clinistix<br /> (if available), stop clock<br /> • samples of any other drinks such<br /> as cola; these should be in<br /> labelled beakers but should not<br /> have their ingredients labels with<br /> them; the drinks will be used to<br /> find their sugar content<br /> • graph paper<br /> ‘diet’ lemonade<br /> carbonated water, citric acid,<br /> flavouring, acidity regulator: sodium<br /> citrate; artificial sweetener:<br /> aspartame; preservative: sodium<br /> benzoate; stabiliser: carboxymethyl<br /> cellulose<br /> ‘ordinary’ lemonade<br /> carbonated water, sugar, citric acid,<br /> flavouring, preservative: sodium<br /> benzoate; artificial sweetener:<br /> saccharin<br /> 2. Knowledge of food labelling will show thatsugarappears before the<br /> artificial sweeteners and citric acid in the ‘ordinary’ lemonade. ‘Ordinary’<br /> lemonade has a certain amount of dissolved sugar in it whereas ‘diet’<br /> lemonade does not. Using the knowledge gained from Task 1, pupils<br /> need only to weigh equal volumes of the two samples to discover which<br /> is which. 10 cm<br /> 3<br /> of ‘ordinary’ lemonade does indeed have a greater<br /> mass than 10 cm<br /> 3<br /> of ‘diet’ lemonade (‘ordinary’ lemonade has a greater<br /> density than ‘diet’ lemonade).<br /> Task 3<br /> 1. graph; make sure that a suitable scale is used for the vertical axis.<br /> 2. ~10.3 g<br /> 3. This will vary depending on which drinks you have chosen to test.<br /> <br /> pupil activity S5 SWEETER THAN SUGAR<br /> There are a number ofartificial sweetenersavailable to consumers. The most<br /> common examples are the very small 'tablets', each equivalent to a teaspoon of<br /> sugar which many people use to sweeten tea and coffee drinks. Sweeteners arealso<br /> available in agranulatedform (it looks like ordinary sugar) for use in cooking and for<br /> sprinkling over food. Again, one teaspoon of the granulated sweetener has the<br /> equivalent sweetness of one teaspoon of sugar.<br /> SAFETY NOTE<br /> YOU MUST NOT EAT OR DRINK ANY OF THE<br /> SUBSTANCES USED IN THIS INVESTIGATION<br /> Task 1<br /> You are given samples of sweetener tablets, a granulated sweetener and ordinary<br /> sugar (sucrose).<br /> 1.Find out, from the labels the chemical names of the artificial sweeteners .<br /> 2.Find the mass of four of the small tablets.<br /> 3.Find the mass of four teaspoons of the granulated sweetener.<br /> 4.Find the mass of four teaspoons of ordinary sugar.<br /> 5. What do you notice? How do you explain this?<br /> 6.Dissolve the four teaspoons of granulated sweetener in 100 cm<br /> 3<br /> of water.<br /> Find the mass of 10 cm<br /> 3<br /> of this solution as accurately as you can.<br /> 7. Dissolve the four teaspoons of sugar in 100 cm<br /> 3<br /> of water. Find the mass of 10 cm<br /> 3<br /> of this solution as accurately as you can.<br /> 8. What do you notice? How do you explain this?<br /> Task 2<br /> Artificial sweeteners can be used in the production of so-called 'diet' drinks, such as<br /> 'diet' lemonade and 'diet' cola.<br /> You are given the empty bottles, or labels, from two bottles of lemonade. One ofthen<br /> is 'diet' lemonade and the other is 'ordinary' lemonade.<br /> 1.Copy, into a table, the ingredients in each lemonade, in the order they appear.<br /> Remember- the ingredients are shown indescending order of mass, i.e. the<br /> ingredient present in the largest amount is alwaysfirst.<br /> 2.You are now given samples of the liquids from each bottle, but you do not know<br /> which is which! Using only the information you have learnt so far, devise a simple<br /> way of finding out which sample is 'ordinary' lemonade and which sample is 'diet'<br /> lemonade. Do not use up all of the lemonades.<br /> Explain your test and the results.<br /> 3.Carry out the Benedict's test (and/or the Clinistix test) on a small sample of each<br /> liquid to confirm your results.<br /> <br /> SWEETER THAN SUGAR pupil activity S5<br /> Task 3<br /> You are given information about themassof different sugar solutions.<br /> Amount of sugar (g) Mass (g) of 10 cm<br /> dissolved in 100 cm<br /> 3<br /> this solution<br /> of water<br /> 3<br /> of<br /> 0 9.94<br /> 2 10.01<br /> 6 10.14<br /> 10 10.28<br /> 14 10.41<br /> 18 10.55<br /> 22 10.68<br /> 1. Plot a graph of this information. Put the amount of sugar dissolved (g) along the<br /> bottom (x axis). Put the mass of 10 cm<br /> 3<br /> of solution up the side (y axis).<br /> Remember to give your graph a title. Label the axes.<br /> 2.Use your graph to predict the mass of a solution containing 10.5 g of sugar.<br /> You are now given some samples of drinks.<br /> 3.Find the mass of 10 cm<br /> 3<br /> of each of the samples. Use your graph to find out<br /> how much sugar is in each of the drinks. Record your results in a suitable<br /> table. Do all drinks contain the same amount of sugar?