Energy & Heat Crystal Gray Joshua Osborne Samuel Anum Maurice Torrance

What is energy? Energy Energy - the ability to do work or produce heat ~Potential energy ~Potential energy – energy due to the composition of an object (type of atoms, number and type of chemical bonds joining the atoms, and the arrangement) ~Kinetic energy ~Kinetic energy is energy in motion *As temp. increases, the motion of submicroscopic particles increase As temp. decreases, the motion of submicroscopic particles decrease

Law of Conservation of Energy aka 1 st Law of Thermodynamics Law states that in any chemical reaction / physical process, energy can be converted from one form to another, but its neither created nor destroyed Law states that in any chemical reaction / physical process, energy can be converted from one form to another, but its neither created nor destroyed

What is heat? Heat Heat – form of energy that flows from a warmer object to a cooler object Represented by q calories Measure Heat with calories. calorie ~calorie (cal) – amount of heat req. to raise the temp. of 1g of pure water by 1°C Calorie ~Calorie (nutritional) – equals 1,000 calories or 1 kilocalorie (kcal) Joule ~Joule (J) – SI unit for heat and energy

Conversion Factories 1 J = cal 1cal = J 1Calorie = 1 kcal

Specific Heat The specific heat of any substance is the amount of heat required to raise the temp.of one gram of that substance by one degree Celsius. The specific heat of any substance is the amount of heat required to raise the temp.of one gram of that substance by one degree Celsius. Different substances have different compositions. Different substances have different compositions. Each substance has its own specific heat. Each substance has its own specific heat.

Calculating heat absorbed Equation for calculating heat: q= c x m x T. Equation for calculating heat: q= c x m x T. q= The heat absorbed or released q= The heat absorbed or released c= The specific heat of the substance. c= The specific heat of the substance. m= The mass of the sample in grams. m= The mass of the sample in grams. T= The change in temperature in degrees Celsius, or T(final) – T(initial). T= The change in temperature in degrees Celsius, or T(final) – T(initial).

Calculating heat released Substances can both absorb and release heat. Substances can both absorb and release heat. The same equation for q can be used to calculate the energy released by substances when they cool off. The same equation for q can be used to calculate the energy released by substances when they cool off.

Using the sun’s energy Radiation from the sun could supply all the energy needs of the world and reduce or eliminate the use of carbon dioxide-producing fuels, but several factors have delayed the development of solar technologies. Radiation from the sun could supply all the energy needs of the world and reduce or eliminate the use of carbon dioxide-producing fuels, but several factors have delayed the development of solar technologies.

Chapter 15.2 pt.2 Maurice Torrance

Heat Main Idea: The enthalpy charge for a reaction is the enthalpy of the products minus of the reactants. Main Idea: The enthalpy charge for a reaction is the enthalpy of the products minus of the reactants. Calorimeter: an insulated device used for measuring the amount of heat absorbed or released during a chemical or physical process. Calorimeter: an insulated device used for measuring the amount of heat absorbed or released during a chemical or physical process. You determine specific heat by using q=(c)(m)deltaT You determine specific heat by using q=(c)(m)deltaT

Chemical Energy and the universe Thermochemistry: The study of heat change that accompany chemical reaction and phase changes Thermochemistry: The study of heat change that accompany chemical reaction and phase changes The system is the specific heat part of the universe The system is the specific heat part of the universe Everything in the universe other than the system is considered surrounding. Everything in the universe other than the system is considered surrounding. Universe=system+surroundings Universe=system+surroundings

Enthalpy To more easily measure and study the energy changes that accompany reactions, chemists defined a property called enthalpy To more easily measure and study the energy changes that accompany reactions, chemists defined a property called enthalpy Enthalpy is the heat content of a system Enthalpy is the heat content of a system The equation to find enthalpy is H = H final – H intial or H= H products - H reactants The equation to find enthalpy is H = H final – H intial or H= H products - H reactants

How to spot signs of enthalpy of reaction In an exothermic reaction enthalpy changes are always negative because the H products is less than H reactants In an exothermic reaction enthalpy changes are always negative because the H products is less than H reactants In an endothermic reaction enthalpy changes are always positive because the H products are more than the H reactants In an endothermic reaction enthalpy changes are always positive because the H products are more than the H reactants Always remember that H = q as long as the pressure is constant Always remember that H = q as long as the pressure is constant

Enthalpy Diagram

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