OCR Gateway Chemistry controlled assessment research Essay Example

the solid and triggers an exothermic chemical reaction using chemicals such as AY, MGM, Zen or OFF.The Blackwell heater-meal system utilizes the reaction of magnesium and salt water to produce hydrogen. The chemical equation for the reaction is MGM (s) + AH (l) > MGM+ (as) + H2O(g) t + AH- (as). The letters s, l, g and as denote solid, liquid, gaseous and in solution states respectively. The reaction is initially slow due to visitation. Iron and salt are added to speed it up. Visitation is a process where a material becomes less reactive by forming a layer of oxide on its surface. To initiate heating, the self-heated can contains three containers – one for the beverage, another for the heating agent and the last for water, separated by a thin breakable membrane. When the user presses on the bottom of the can, a rod pierces the membrane allowing water and heating agents to mix, resulting in an exothermic reaction that releases heat and warms the beverage. Exothermic reactions transfer energy to the surroundings. Source 5 houses chemicals that react exothermically when combined.Exothermic reactions involve the transfer of energy as heat, which causes an increase in temperature in both the reaction mixture and its surroundings.This rise in temperature can be measured with a thermometer.Examples of exothermic reactions include combustion (burning), oxidation reactions (such as rusting), and neutralization reactions involving acids and alkalis.Some everyday applications of exothermic reactions include hand warmers and self-heating cans for beverages, which can reach high temperatures and release energy per gram in these chemical reactions. Self-heating cans, for instance, use a mixture of water and calcium oxide that, when activated,

heats up the beverage by 50 to 55 degrees Celsius within three minutes.The outer shell of the can also insulates the drink for approximately 45 minutes and ensures safety by preventing burns.The military uses magnesium and iron heaters in their Meals Ready to Eat or ration heaters.These heaters generate 310 calories per gram of heat energy upon activation and release hydrogen as a byproduct.Analogous items for civilians are also available, although it is rare to find individual packets sold by legitimate sellers.