© KCL/PENTECH/WCED 2000 Day length Energy in food Much of the energy that we gain from food is stored in fruits and vegetables in the form of sugar and starch. Fruits, seeds and roots can be tested with chemicals to find out if they contain sugar and starch. TEST for STARCH TEST for SUGAR 1) Take some food (for example banana) and cut it into small pieces. 2) Put it into a test tube and half fill the tube with BENEDICTS solution. 3) Heat the tube in a beaker of boiling water. 4) If the Benedicts solution changes colour from blue to red then sugar is present in the food. 1) Take some food (for example potato) and cut it open on a dish. 2) Put a few drops of IODINE solution on the food. 3) If the colour of the iodine changes from yellow to black then STARCH is present in the food. DRAW pictures to show how to do these food tests. 1.

© KCL/PENTECH/WCED 2000 Day length Energy in food Brian and Rashida tested seven different kinds of food for starch and sugar. They recorded the results of their experiments into a table. Food tested Colour with Benedict’s They then used the results to try to make conclusions about how energy was being stored in these foods. Please try to help Brian and Rashida by WRITING YOUR CONCLUSIONS into the table below. Say 'yes' or 'no' whether sugar or starch was present in the food and which part of the plant it came from, e.g. root,stem, fruit, seed. Rice Apple Bread Carrot Corn/Mealies Crisps/Chips Colour with iodine blackblue yellowred blackred yellowred blackred blackblue Food tested Rice Apple Bread Carrot Corn/Mealies Crisps/Chips Is sugar present Is starch present Part of plant 2.

© KCL/PENTECH/WCED 2000 Day length Energy in food The energy stored in food is measured in the units of kilojoules (kJ). The table below shows some different foods and the number of kilojoules contained in one gram of each type. Use the information in the table to DRAW a bar chart. WRITE the name of the food on each bar. A) bread 10 B) jam 11 C) cheese 18 D) milk 3 E) egg 6 F) fruit cake G) nuts H) boiled rice I) lettuce L) fried potato/crisps K) boiled potato J) carrot ABCDEFGHI J K L type of food kilojoules per gram DISCUSS what other substance might be in the foods which store the most energy. 3.

© KCL/PENTECH/WCED 2000 Day length Energy in food The amount of energy you need to get from food each day depends on how big you are, how much exercise you do and how fast you are growing STUDY the graph which shows the energy needed by different types of people.. 10,000 kilojoules per day Brian aged 12 years male miner female office worker Rashida aged 12 years male teacher pregnant woman 5,000 15,000 DESCRIBE what the graph shows in your own words. 4.

© KCL/PENTECH/WCED 2000 Day length Energy in food Rashida is a 12 year old girl. The average energy needed by a girl her age is 9,700kJ each day. Rashida kept a record of all the food she ate in one day. She went to the library and found out how much energy each meal provided. STUDY the table of energy in food that she made. WRITE a letter to Rashida to tell her: - how much energy she got from her food that day, - should she try to eat more or less tomorrow, - what might she eat more of ? Rashida’s food energy in kJ cereal400 milk600 chocolate bar1500 cheese sandwich 1800 crisps/chips 600 fruit juice 700 lamb curry1200 boiled rice500 roti900 yoghurt400 banana 300 cola600 breakfast lunch dinner 5.