Step-by-step explanation:
Thermal energy is defined as the internal energy of an object because of the kinetic energy present within the molecules of the object.
As relation between kinetic energy and temperature is as follows.
K.E =
![(3)/(2)kT](https://img.qammunity.org/2020/formulas/chemistry/middle-school/7zm8chkufqhk79dbvu50iua7630aehpsxs.png)
So, with increase in temperature there will also occur an increase in kinetic energy which leads to an increase in thermal energy of the substance.
Therefore, we can conclude that by applying heat, Bela increased the thermal energy of the eggs. She could measure how much the temperature increased with a thermometer.