what is the change in thermal energy of the block of aluminum A) 187 J B) 2,590 J C) 5820 J D)187,000 JThe temperature of a 24.5-g block of aluminum decreases from 30. degree C to 21.5 degree C if...

what is the change in thermal energy of the block of aluminum

A) 187 J

B) 2,590 J

C) 5820 J

D)187,000 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

Asked on

2 Answers | Add Yours

Top Answer

ndnordic's profile pic

Posted on

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

mlsiasebs's profile pic

Posted on

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.

 

We’ve answered 324,761 questions. We can answer yours, too.

Ask a question