Chemistry L1.pdf

Chemistry ⋆ Temperature : average of kinetic energy. (Temperature is proportional to the kinetic energy). Energy : ability to do work or produce heat. Energy : kinetic energy / potential energy. constant random motion....

Chemistry ⋆ Temperature : average of kinetic energy. (Temperature is proportional to the kinetic energy). Energy : ability to do work or produce heat. Energy : kinetic energy / potential energy. constant random motion. Composition or position. Chemical systems contain both kinetic energy and potential energy.  Composition : type of atoms, number and type of chemical bonds, and how atoms are arranged. The law of conservation of energy : states that in any chemical reaction or physical process, energy is neither created nor destroyed, but can change from one form to another. Law of conservation of energy ---> First law of thermodynamics Potential energy : Maximum (8J) PE + KE = 8J Kinetic energy : Zero (0J) 8+0=8 Potential energy : Decreasing (4J) PE + KE = 8J Kinetic energy : Increasing (4J) 4+4=8 Potential energy : Zero (0J) PE + KE = 8J Kinetic energy : Maximum (8J) 0+8=8 Potential energy : PE, Kinetic energy : KE Their sum is constant  Chemical potential energy : is energy stored in a substance because of its composition. Chemical potential energy is released or absorbed as heat during chemical processes or reactions. Chemical potential energy plays an important role in chemical reactions. Combustion reaction : Heat : is energy that is in the process of flowing from a warmer object to a cooler object. Heat ---> q Heat can be measured in calorie. A calorie (cal) : is defined as the amount of energy required to raise the temperature of one gram of pure water by one degree Celsius (1°C). 10°C 1 cal 11°C Heat it up 1g of pure water 1g of pure water The energy content of food is measured in nutritional Calories. 1 nutritional Calorie equals 1000 calories, or 1 kilocalorie (kcal). Joule (J) : SI unit of energy and heat. 1 J = 0.239 cal 1 cal = 4.184 J 1 Calorie = 1000 cal / 1 Kcal The specific heat (C) of any substance : is the amount of heat required to raise the temperature of one gram of that substance by one degree Celsius. Specific heat can be measured in J/g °C Because different substances have different compositions, each substance has its own specific heat.  cal or J J/g °C g K or °C Specific heat Mass Change in temperature Heat absorbed or released / Energy Final temperature minus initial temperature Have a nice day ⋆