Question

Calculate the energy of 1kg of concrete from 20⁰c to 30⁰c​

Answer 1

Answer:

9 kilojoules of energy are stored in a kilogram of concrete due to sensible heat.

Explanation:

In this exercise we need to determined the sensible heat store in a kilogram of concrete due to a change in temperature. Sensible heat ($Q$), measured in kilojoules, is defined by the following expression:

$Q = m\cdot c\cdot (T_{f}-T_{o})$ (1)

Where:

$m$ - Mass, measured in kilograms.

$c$ - Average specific heat of concrete, measured in kilojoules per kilogram-degree Celsius.

$T_{o}$, $T_{f}$ - Initial and final temperatures of concrete, measured in degrees Celsius.

If we know that $m = 1\,kg$, $c = 0.9\,\frac{kJ}{kg\cdot ^{\circ}C}$, $T_{o} = 20\,^{\circ}C$ and $T_{f} = 30\,^{\circ}C$, then the energy store in a kilogram of concrete is:

$Q = (1\,kg)\cdot \left(0.9\,\frac{kJ}{kg\cdot ^{\circ}C} \right)\cdot (30\,^{\circ}C-20\,^{\circ}C)$

$Q = 9\,kJ$

9 kilojoules of energy are stored in a kilogram of concrete due to sensible heat.