Charlene Sci 7.3 PDF - Respiration - Practical 7.8

—_— A Food as a source of energy VY Flipped classroom ; rr Watch a video Food provides energy for supporting our body ac...

—_— A Food as a source of energy VY Flipped classroom ; rr Watch a video Food provides energy for supporting our body activities like running, and answer & reading and working. Even when we sleep, we still need energy to the questions. breathe and keep our heart beating. In living things, the energy stored in food is released and converted to other forms of energy to support their body activities. Let us carry out Practical 7.8 to study the release of energy from food. @ P r a c t i c a l 7. 8\ Bu rn in g fo od Aim To study the release of energy from food Apparatus and materials per group boiling tube 1 stand and clamp 1 set alcohol thermometer 1 two-holed stopper ba y | burning spoon 1 gas lighter 1 | Bunsen burner 1 peanut 1 insulating mat 1 1 Fill a boiling tube with water until it is one-third full. Stopper the boiling tube with a two-holed stopper Li | alC and insert an alcohol thermometer into the water. thermometer Fix the boiling tube on the stand with a clamp.. 13. i two-holed 2 Caution Sy e Do not clamp the boiling tube too tightly. boiling tute containing water Otherwise, it may break. e Do not let the bulb of the thermometer touch the bottom of the boiling tube. 2 Record the initial water temperature (T)). 3 Put a peanut into a burning spoon and heat it over a Bunsen flame until it burns. () Wear safety spectacles! 36  Respiration 4 When the peanut starts burning, move the burning spoon to the bottom of the boiling tube. ; Move the spoon around in circles. Heat the wk Spoon peanut with a Bunsen flame again if the peanut goes out before it is completely burnt. burning peanut Caution dei; move around In circles Avoid heating the boiling tube near the bulb of the thermometer directly. 5 When the peanut is completely burnt, put the burning spoon on the insulating mat. - Record the final water temperature (T5). Results Initial water temperature (T)) Final water temperature (T)) 0) Discussion What can you tell from the results? When food is burnt, energy IS (is / is not) released. |” ‘ “ Did you know? (» } Energy value of food The energy value* of food shows the amount of energy provided by a certain quantity of the food. It is often expressed in kilocalories (kcal) or kilojoules (kJ). 1 kcal = 4.2 kJ. The energy value of some pre-packaged foods is shown on their nutrition labels® (Fig 7.15). Read the nutrition labels of some foods and compare their energy values. NUTRITION FACTS / S&H Servings Per Package / BIBAMIRFAZRNE ) Serving Size / RAM | 236 mi RH | A WX P W J : Splat aos gel mn } 5 er 3 Yi / Protein / EAR 3.09/% Total Fat / AEH 39¢/3 9.2g/% -Saturated fat / R055 249/% 5.79/% -Trans fat / RiUEY 0.1g9/% 0.2g9/% Cholesterol / RER 14 mg /&R 33 mg /AR Carbohydrates/ Rk{t&% 47g/R 11.19/38. =Sugars/# 4.79/% Migs 9 Dietary Fiber / HRN 0g/R Cg/R 5 AOAHAD Sodium / AR 35 mg /&R 83 mg /&R Phare Calcium / BR 94mg /BR 221 mg/AR AE Phosphorus / 5% 87Tmg/gR 205mg/ER Vitamin 812/M#t#812 0.32ug/m® 0.76 ug/mR Vitamin 82 / Nft®82 ~o0timg/mR 0 TTT LL TL TT TT TT TTT Pr spp rrr rrprrsrrrrryrrrrerrrrrersrorrrrersrrrrrrrey YT TTX TDI T FATAL TA LE DAS RES ERX EX DNL FX YR DYN T YE AA LAN TRAN RRA LL ARAL AA Rd Said th iid bid di inhibit AE ARS Rd EE RR RA LR ES RL AARNE EY energy value ERE nutrition label & ZH 15 4%  (33 Obtaining energy from food by respiration In Practical 7.8, we learnt that energy is released when food burns. In living things, energy in food is released gradually when food is broken down through a process called respiration Respiration occurs inside cells. During respiration, some of the chemical energy stored in food (glucose) is converted to other useful forms of energy to support body activities. Oxygen is usually needed in the process. Carbon dioxide and water are usually produced. cell Fig 7.16 The process of respiration Respiration involves a series of controlled chemical reactions. The equations below summarize the process. (orb cc ne WA in food is then converted to other G6 o Chemical equation of respiration: useful forms of 4. ais pe I;