How much heat is required to completely melt 2.5 kg of ice that has a temperatur

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You have 2.5 lg of ice at -40C and you want to convert it into water at 0C. So, the first step is to map the changes. Step 1 Step 2 Step 3 Ice at -40C ----------> Ice at 0C --------> Water at 0C Step 1: Bringing Ice to temperature of fusion. Using Q=m*Cp*dT with Cp=2.1 J/g.C, Q1=2500*2.1*(0-(-40))= 21000 J I would point out that dT= T final -T initial. This is crucial as it would change the sign of the heat transfert. The signification of this is that, if it is a + sign, we GIVE energy to the system and , if it is a - sign, we REMOVE energy to the system. In other word, + = Heat // - = Cool. In this exercice, we are heating, so +. Step 2: Melting of Ice. Using Q = m*L with L= 334 J/g, Q2= 2500*334 = 835000 J The change in state (From solid to liquid) is always an energy demanding step.

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