7Ia-1 Energy from food Cut out these cards and match them up to make correct sentences. Arrange the sentences in a sensible order, and stick them into your book. explain why different people need different amounts of energy from foods. A teenager needs less energy in units called joules. A teenager needs more energy from food. Energy is measured in units called calories. Energy used to be measured is given on the food label. Our bodies get energy than a very active adult. Our bodies need energy than an adult with an office job. The amount of energy stored in food the more energy your body needs. The faster you are growing the more energy your body needs. The more active you are to grow, repair, move and keep warm. Pearson Education Ltd 2014. Copying permitted for purchasing institution only. This material is not copyright free. 1
7Ia-2 Energy in food 1 Name Class Date Your teacher may watch to see if you can: read the scale on a thermometer work safely with burning materials. Aim You are going to compare the amounts of energy stored in different foods. Introduction Our bodies get the energy we need from the energy stored in food. Different kinds of food store different amounts of energy. Method Apparatus different kinds of food measuring cylinder eye protection Bunsen burner cork pin water thermometer clamp stand boiling tube Wear eye protection. Do not eat any of the foods. Label this diagram using words from the box. boiling tube cork food pin thermometer water Fill in the missing words using words from the box below. A I will heat some water using the energy from a. B I will make it a fair test by using the and holding the burning food the same C I will measure the volume of the water using a pour it into a boiling tube. amount of water each time from the boiling tube. and D I will measure the temperature of the water using a. E I will the experiment with the other foods. distance measuring cylinder piece of food repeat same thermometer Page 1 of 2 Pearson Education Ltd 2014. Copying permitted for purchasing institution only. This material is not copyright free. 2
7Ia-2 Energy in food 1 Recording your results 1 Record your results in the table. Food Temperature at the beginning ( C) Temperature at the end ( C) Temperature difference ( C) Considering your results/conclusions 2 When the food burned the energy stored in it was transferred to the water and made it hotter. The food that gave the highest temperature was the. This is the food which stores the energy. carry out a fair investigation draw a conclusion. Page 2 of 2 Pearson Education Ltd 2014. Copying permitted for purchasing institution only. This material is not copyright free. 3
7Ia-3 Energy in food 2 Your teacher may watch to see if you can: read the scale on a thermometer work safely with burning materials. Aim You are going to compare the amounts of energy stored in different foods. Introduction One way to find out how much energy is stored in a food is to burn it. As the food burns, the energy stored in it is transferred to heat. This can be used to heat water. The hotter the water gets the more energy has been transferred from the food. Method Apparatus pieces of different foods clamp stand water boiling tube eye protection pin or wire spiral in a cork sharp knife thermometer Bunsen burner balance measuring cylinder Wear eye protection. Do not eat any of the foods. Wash hands after handling the foods. A Choose three different types of food. B Draw a results table like this: Food Temperature at beginning ( C) Temperature at end ( C) Mass of food and pin at beginning (g) Mass of food and pin at end (g) C Put food on the pin (or into the spiral) and find the mass of the cork, pin and food together. Write this in your table. D Use the measuring cylinder to measure 10 cm 3 of water, and put it into the boiling tube. Record the temperature of the water. E Light the food using the Bunsen burner, and hold the burning food under the boiling tube. Make sure the flame is touching the test tube. F When the food has finished burning record the temperature of the water again. Let the food cool down and find the total mass of the cork, pin and the food remaining on it. G Repeat for the other foods. 1 Describe how you carried out the practical. How did you make it a fair test? 2 Draw a neat diagram of the experiment. Page 1 of 2 Pearson Education Ltd 2014. Copying permitted for purchasing institution only. This material is not copyright free. 4
7Ia-3 Energy in food 2 Recording your results 3 a Calculate the temperature change for each food. b Calculate the change in mass for each food (this is the mass of food that actually burnt during your investigation). c Divide each temperature change by the mass change, to find out the temperature rise per gram of food. d Present the results of your calculation in a table. 4 Draw a bar chart to show your results. Considering your results/conclusions 5 Which food contained the most energy? How do you know? 6 Foods come in different sized pieces. How could this have affected your results? Evaluation 7 Did all the energy transferred from the burning food go into the water? Explain your answer. 8 Suggest how you could improve the experiment. plan a fair investigation present data as a bar chart evaluate my methods. Page 2 of 2 Pearson Education Ltd 2014. Copying permitted for purchasing institution only. This material is not copyright free. 5
7Ia-4 Comparing foods Paul investigated the energy transferred by different snacks when they are burnt. The table below shows his results. Food Mass burnt (g) Temperature rise ( C) salted peanuts 4.0 24 cashew nuts 3.0 18 sunflower seeds 2.0 12 raisins 5.0 15 dried apricots 15.0 27 Temperature rise per gram of food ( C/g) 1 Copy the table and complete the last column to show the temperature rise per gram of food. 2 Write the foods in order of the temperature rise, starting with the one that had the smallest temperature rise per gram of food burnt. 3 a Explain why it is useful to work out the temperature rise per gram. b Explain why it is useful to write the foods in order of temperature rise per gram. 4 Work out the ratios of the temperature rise per gram obtained with: a dried apricots and sunflower seeds b raisins and cashew nuts. Write your ratio in the form 1 : n. 5 Write out in words what the answer to question 4a tells you. 6 The tables show part of the labels from a packet of raisins and a packet of dried apricots. Raisins: typical values 100 g contains 1 serving (20 g) contains energy 1240 kj 250 kj Dried apricots: typical values 100 g contains 1 serving (30 g) contains energy 755 kj 225 kj a b c Compare the energy per 100 g of the two foods. Compare the energy per serving of the two foods. Why do you think that food packets usually give the energy per 100 g and the energy per serving? make a fair comparison of experimental results calculate ratios. Pearson Education Ltd 2014. Copying permitted for purchasing institution only. This material is not copyright free. 6
7Ia-5 Food cards 1 Cut out the cards. 2 How much energy do you think each kind of food provides? Sort the cards into three groups (high, medium, low) according to the amount of energy you think each type of food stores. 3 How can you find out if your grouping is correct? recall foods that store a lot of energy. apple white bread peas baked beans banana carrots lemonade boiled egg lamb beef white toast pear tomatoes wholemeal bread margarine chips boiled potato cheese pitta bread orange milk baked potato chicken orange juice tea with milk coffee with milk water cornflakes chapattis poppadum lentil dahl fried egg hamburger Pearson Education Ltd 2014. Copying permitted for purchasing institution only. This material is not copyright free. 7
7Ia-6 Energy and you 1 Name Class Date 1 Look at the food labels below, then fill in the table. Type of food cereal jam Energy value in 100 g (kj per 100 g) Energy value in one serving (kj per serving) yoghurt sausages bread butter 2 Which food gives the most energy per 100 g? 3 Which food gives the most energy per serving? 4 a How much energy would you get if you had a slice of bread and butter with jam on it? Show your working. b How much energy would you get if you ate a sausage sandwich made with two sausages? Show your working. understand food labels work out how much energy different meals contain. Pearson Education Ltd 2014. Copying permitted for purchasing institution only. This material is not copyright free. 8
7Ia-7 Energy and you 2 Look at the six food labels. 1 How many joules are there in a kilojoule? 2 Explain why we need stored energy in our bodies. 3 a Draw a table like the one below. Fill in the table using information from the labels above. Type of food Energy value in 100 g (kj per 100 g) Energy value in one serving (kj per serving) b Which food supplies the most energy per 100 g? 4 a Which food supplies the most energy per serving? b Why is this a different food to the one with the most energy per 100 g? 5 Collect four labels of your own and complete a similar table. 6 Did you find any labels that did not have energy values on them? If so, what were they? use food labels to compare the energy in different foods. Pearson Education Ltd 2014. Copying permitted for purchasing institution only. This material is not copyright free. 9
7Ia-8 Climbing the Matterhorn John Tyndall (1820 1893) was born in Ireland. He was a surveyor and a railway engineer before becoming a scientist. One of the things he was interested in was studying glaciers, and he went to the Alps nearly every year. He was the first person to reach the top of the Weisshorn (4505 m high), and climbed Mont Blanc (4807 m) several times. In 1860 he had attempted to climb the Matterhorn (4478 m) and reached nearly 4000 m before having to turn back but that was the highest anyone had ever been at the time. There is a story that Tyndall calculated that the amount of energy needed to climb the Matterhorn was contained in a ham sandwich, so that was all the food he took with him! We can do some rough calculations to see if he was right, and if we think the story is true. Forces are measured in newtons (N), so the weight of a person or an object is measured in newtons. Page 1 of 2 Pearson Education Ltd 2014. Copying permitted for purchasing institution only. This material is not copyright free. 10
7Ia-8 Climbing the Matterhorn 1 a How high would Tyndall have climbed if he started from Zermatt? Remember that he was aiming for the top! b How much energy would it take to lift his total weight this far? Give your answer in kilojoules. 2 a How much energy would Tyndall have needed just to stay alive for 2 days? b What is 10% of this amount of energy? c How much extra energy would Tyndall have needed for the climbing he was going to do? (Hint: round your answer to question 1a up to the nearest 1000 m, then divide by 500 to find out how many lots of 10% you need to add. Multiply this answer by your answer to part b.) d The Matterhorn usually has ice and snow on it, and Tyndall was probably carrying a rucksack. How much extra energy would he need for these reasons? e How much total energy would he have needed? 3 Now work out how much energy is stored in a ham sandwich. (Remember there are usually two slices of bread!) 4 a How does the energy in a ham sandwich compare with your answer to question 1b? b How many sandwiches would Tyndall have had to take if he only needed the energy you calculated in question 1b? 5 a How does the energy in a ham sandwich compare with your answer to question 2e? b Do you think John Tyndall really set off up the Matterhorn with only a ham sandwich? Try to explain your answer. choose the correct data to carry out calculations. Page 2 of 2 Pearson Education Ltd 2014. Copying permitted for purchasing institution only. This material is not copyright free. 11