CONCERNING COLD PACKS INTRODUCTION Examples of the use

CONCERNING COLD PACKS

INTRODUCTION Examples of the use of chemical in daily life • Exothermic reaction ØUsing heat packs in cold weather • Endothermic reaction ØUsing cold packs to relieve pain and swelling

INGREDIENTS Ingredients of a cold bag • Consists of two bags • Outer bag contains water • Inner bag (or tube) contains ammonium nitrate or sodium thiosulphate

CHEMICAL PRINCIPLE • Squeeze the package and break the bags • Ammonium nitrate dissolves in water • Give an endothermic reaction ØAbsorb heat from the surrounding ØLower the pack’s temperature NH 4 NO 3(s) + aq NH 4+＋(aq)+NO 3 -(aq) △H= +25. 5 k. J mol- 1

HOW DOES A COLD PACK WORK? • Injuries swell as fluid leaks from blood vessels • Cold causes vessels to constrict • Less fluid leaks from blood vessels, the less swelling • Cold also eases inflammation and muscle spasms • Thus, cold packs are very effective at reducing swelling

HOW TO USE A COLD PACK? • Ready-to-use • Easily activated for emergency use where cold therapy is required • Squeezes the inner bag and release the water into the crystals in the outer bag • It will reach 0 degrees Celsius • Cold lasts from about 20 -40 minutes • Apply cold packs for periods of up to 20 minutes every two to four hours

APPLICATIONS • Help to relieve pain and swelling • For preservation of amputated limb • For first-aid treatment on sport injuries • Insect bites, small burns, and repetitive strain injuries • Help people with muscle spasms, chronic back pain, and various forms of arthritis

GROUP MEMBERS ABBY LAU VIVIAN TANG AMY WONG THIS IS THE END OF THE PRESENTATION HOPE YOU ENJOY IT AND HAVE A NICE DAY!