Solve It in .NET

Encoder EAN / UCC - 13 in .NET Solve It

Heat is a form of energy that flows from warmer objects to cooler objects But how much heat can an object hold If objects have the same heat content, does that mean they re the same temperature You can measure different temperatures, but how do these temperatures relate to heat flow These kinds of questions revolve around the concept of heat capacity, the amount of heat required to raise the temperature of a system by 1K It takes longer to boil a large pot of water than a small pot of water With the burner set on high, the same amount of heat flows into each pot, but the larger pot of water has a higher heat capacity So, it takes more heat to increase the temperature of the larger pot You ll encounter heat capacity in different forms, each of which is useful in different scenarios Any system has a heat capacity But how can you best compare heat capacities between chemical systems You use molar heat capacity or specific heat capacity (or just specific heat) Molar heat capacity is simply the heat capacity of 1 mole of a substance Specific heat capacity is

simply the heat capacity of 1 gram of a substance How do you know whether you re dealing with heat capacity, molar heat capacity, or specific heat capacity Look at the units Heat capacity: Energy / K Molar heat capacity: Energy / (mol K)

Specific heat capacity: Energy / (g K) Fine, but what are the units of energy Well, that depends The SI unit of energy is the joule (J) (see 2 for more about the International System of units), but the units of calorie (cal) and liter-atmosphere (L atm) are also used Here s how the joule, the calorie, and the liter-atmosphere are related: 1J = 02390 cal 1013J = 1 L atm Note that in everyday language, a calorie actually refers to a Calorie or a kilocalorie a calorie of cheesecake is 1,000 times larger than you think it is Calorimetry is a family of techniques that puts all this thermochemical theory to use When chemists do calorimetry, they initiate a reaction within a defined system, and then measure any temperature change that occurs as the reaction progresses There are a few variations on this theme Constant-pressure calorimetry directly measures an enthalpy change ( H) for a reaction because it monitors heat flow at constant pressure: H = qP Typically, heat flow is observed through changes in the temperature of a reaction solution If a reaction warms a solution, then that reaction must have released heat into the solution In other words, the change in heat content of the reaction (qreaction) has the same magnitude as the change in heat content for the solution (qsolution) but has opposite sign: qsolution = qreaction So, measuring qsolution allows you to calculate qreaction, but how can you measure qsolution You do so by measuring the difference in temperature ( T) before and after the reaction: qsolution = (mass of solution) (specific heat of solution) T In other words, q = mCP T Here, m is the mass of the solution and CP is the specific heat capacity of the solution at constant pressure T is equal to Tfinal Tinitial When you use this equation, be sure that all your units match For example, if your CP has units of J g 1 K 1, don t expect to calculate heat flow in kilocalories Constant-volume calorimetry directly measures a change in internal energy ( E, not H) for a reaction because it monitors heat flow at constant volume Often, E and H are very similar values A common variety of constant-volume calorimetry is bomb calorimetry, a technique in which a reaction (often, a combustion reaction) is triggered within a sealed vessel called a bomb The vessel is immersed in a water bath of known volume The temperature of the water is measured before and after the reaction Because the heat capacity of the water and the calorimeter are known, you can calculate heat flow from the change in temperature