name Prelaboratory Assignment: Specific Heat Capacity 1. What are the units for
ID: 556117 • Letter: N
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name Prelaboratory Assignment: Specific Heat Capacity 1. What are the units for heat capacity, specific heat capacity, and molar heat capacity 2. Ifa sample has an initial temperature of 22.15° and a final temperature of 18.45 C, what is AT? Is it any different in kelvin? 3. A 100g piece of metal, initially at 85° C is put (without heat loss or gain) into a cup with 50 g of water, initially at 22° C. Which of the following is true (select all that apply)? For the incorrect statements, explain why they are wrong. a. The temperature of the metal decreases and that of the water increases. b. The temperature change of the metal is equal but opposite that of the water. c. Q for the metal is equal but opposite that of the water d. The heat capacity of the water is positive and that of the metal is negative.Explanation / Answer
1.Heat capacity is defined as the amount of heat required to rise the temperature by 1 deg.c. This is measured in J/deg.c
2. Specific heat capacity is the heat capacity per unit mass of substance. This is measured in J/gm.deg.c
3. molar heat capacity is the heat capacity per unit mole of substance. This is measured in J/mole.deg.c
4. Temperatrue difference = 22.15-18.45=3.7 deg.c when difference is expressed in kelvin,
22.15+273- (18.45+273)= 3.7 , so no diifference between deg.c and K.
5. since metal is at higher temperature than water, metal looses heat and water gains heat.
the temperature change of water and metal are related as
heat lost by metal= heat gained by water or
heat lost by metal = mass of metal* specific heat of metal* temperature difference= 100*Cp*(85-t)
heat gained by water= mass of water* specific heat of water* temperature difference = 50*4.184*(t-22)
heat gained by water = heat gained by water, t is the final temperature, Cp = specific heat of metal
100*Cp*(85-t)= 50*4.184*(t-22)
100*Cp*temperature change of metal = 209* temperature change of water
hence temperature change of metal is not same as temperature change of water.
heat lost by water= -heat gained by metal for adiabatic system
Q= heat lost by water hence Q for metal= -Q for water.
Heat capacity cannot be -ve. since the definition is the heat required to rise the temperature of metal by 1 deg.c. So heat capacity of metal cannot be -ve.
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