of heat absorbed or evolved by physical and chemical processes.2)Heat (q) can be defined as the flow of energy into and out of a system due to atemperature difference between the thermodynamic system and its surroundings.3)Heat energy will flow from the region of higher temperature to the region oflower temperature until thermal equilibrium has been reached.a.At thermal equilibrium, the temperature of the two regions will be equal atany one time.4)Heat and temperature are both measures of kinetic energy but there is animportant difference.a.Heat measures totalenergy.b.Temperature measures the averageenergy.c.An example to distinguish these two terms is as follows.i.Considering a teaspoonful of boiling water versus a cup of boilingwater (both at 100oC), the cup of boiling water would be morehazardous to spill because it has more heat (total energy).5)The formula for heat is as follows: q= s•m•Δta.q= heat, s= specific heat, m= mass, Δt= change in temperature (tf– ti) .i.Specific heat for water = 4.184 J/(g •oC)6)In chemical reactions, heat is often transferred from the “system” to its“surroundings,” or vice versa.a.The substance or mixture of substances under study in which a changeoccurs is called the thermodynamic system (or just the system.)b.The surroundings are everything around that thermodynamic system thatcan interact.7)The sign of qis very important!a.If qis positive, heat is absorbed by the system.i.This process is described as endothermic.b.If qis negative, heat is released from the system.i.This process is described as exothermic.Introduction to Calorimetry:1)Acalorimeter is a device used to measure the heat absorbed or evolved during aphysical or chemical change.2)There are two types of calorimeters:a.A bomb calorimeteris an isolated metal container with a known massand known heat capacity.Experiment #8A Barnett
42b.A coffee cup calorimeteris a plastic–foam cups that serves as a vessel forheat exchange.i.These cups have a very low heat capacity and the small amount ofheat gained/emitted is ignored.ii.The foam is a good thermal insulator that allows very little heat toescape from the calorimeter.3)The essential formula that governs calorimetry is as follows.a.qsystem= –qsurroundingsIntroduction to Heat of Fusion:1)The heat needed to melt 1 mole of a pure substance is called the heat of fusionand denoted as ΔHfus.2)To melt a pure substance at its melting point requires an extra boost of energy toovercome lattice energies.3)The heat of fusion (ΔHfus) can be calculated.a.At constant pressure, the heat exchanged is equal to the heat of fusion:i.qp= ΔHfus.Introduction to Heat of Solution:1)A solution is a homogeneous mixture of two or more substances, consisting ofions or molecules.2)The solute is the dissolved substance for gases or solids in a liquid solution.
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