Heat Calculations with Specific Heat

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Presentation transcript:

Heat Calculations with Specific Heat What is heat? What is energy? How are they both measured?

What is heat? (q) – transfer of energy from one object to another because of temperature difference between objects form of energy flows from warmer to cooler object measured in joules

What is energy? (E) – ability or capacity to do work measured in joules detected by effects

What is temperature? (T) – NOT a form of energy thought of as intensity of heat measured in C, F, or K amount of heat per unit of substance

What is a Joule? (J) – amount of energy produced when a force of 1 Newton acts over a distance of 1 meter small amount of energy 1 Newton ~ amount of force 40 pennies exerts on the palm of your hand striking a match releases 1050 J

What is thermodynamics? THERMODYNAMICS deals with energy changes (∆ E) that accompany chemical and physical properties TELL US whether a reaction is possible depending on: - whether reaction occurs by itself (spontaneously) OR - if reaction needs outside source of energy to proceed

Laws of Thermodynamics

What is heat capacity? energy required to raise temperature of substance by 1 °C Every pure substance has unique heat capacity Expressed as Joules 1 Calorie = 4.184 Joule

What is specific heat? (Cp) energy required to raise temperature of substance by 1 °C Specific Heat varies depending on: Type of substance State of matter of substance (s, l, g) Temperature of the reaction S.H. of ICE = 2060 J/kg°C S.H. of liquid water = 4180 J/kg°C

How do you measure heat? 1. Mathematically using HEAT EQUATION q = m x Cp x ∆T How much energy would be needed to heat .450 kg of Copper metal from a temperature of 25 °C to 75 °C? Specific Heat of Copper at 25 °C = 385 J/kg °C q = m (Cp) ∆T PLUG AND CHUG!

What is a Calorimeter?

You are boiling water to make spaghetti You are boiling water to make spaghetti. When the water boils, does it all instantly vaporize? Why not, after all – it’s reached the boiling point? Video Animation

Heating Curve in Motion

EX. How much heat is necessary to totally melt 5 g of ice at 0 C to liquid water at 0 C? EX. How much heat is necessary to change 5 g of water at 100 C to steam at 100 C? HEAT CALCULATIONS  q = m Cp △T for substance WITHOUT a phase change q = m △Hfus when a substances freezes/melts q = m △Hvap when a substance evaporates/condenses If a substances undergoes a phase change and changes temperature, you must add all the heats together.