A student has two metal blocks, X and Y. Block X is at a temperature of $50\,^{\circ}\text{C}$ and block Y is at $0\,^{\circ}\text{C}$. The two blocks are then put into contact with each other. After a period of time, both blocks reach a temperature of $25\,^{\circ}\text{C}$. What has happened to the internal energy of each block?
- Ainternal energy of X decreased; internal energy of Y decreased
- Binternal energy of X decreased; internal energy of Y increased
- Cinternal energy of X increased; internal energy of Y decreased
- Dinternal energy of X unchanged; internal energy of Y unchanged