what is the change in thermal energy of the block of aluminum
A) 187 J
B) 2,590 J
C) 5820 J
The temperature of a 24.5-g block of aluminum decreases from 30. degree C to 21.5 degree C if aluminum has specific heat of 897 J/kg degree C
2 Answers | Add Yours
Heat energy, Q, is found by the product of the mass of an object times the temperature change times the specific heat of the material.
Q = m * c * delta T
You are given the specific heat of 897 J/kg-degree C
In this case the change in temperature is 8.5 degrees C (30 - 21.5)
But you only have 24.5 g of aluminium, or 0. 0245 kg.
= 8.5 * 897 * 0.0245 = 187 J
Looking for the change in thermal energy means finding the heat change in the sample. For that we use the following equation
q = m * s * deltaT
where q is the heat, m is the mass, s is the specific heat, and deltaT is the change in temperature (final - initial). So that the units will cancel, we need to convert the mass from g to kg by dividing by 1000.
q = (0.0245 kg)(897 J/kg degC)(21.5-30 deg C)
q = (0.0345 kg)(897 J/kg degC)(-8.5 deg C)
The negative sign indicates that the Al is losing energy as it cools but the change is a positive value.
Multiply through the values to find the value of q.
Join to answer this question
Join a community of thousands of dedicated teachers and students.Join eNotes