As of now, the nuclear fission is the most feasible energy source for human use. All the nuclear power plants are based on the controlled nuclear fission reaction, where the unstable nucleus is bombarded with high speed neutrons, thus, splitting the nucleus into stable ones and releasing huge amount of energy. The nuclear fusion requires very high temperature, the temperature equal's to that of the sun. Hence, it is not feasible right now. As the technology advances, we will see advancement in other form of energies.
Answer: The Mohs Hardness Scale is used as a convenient way to help identify minerals. A mineral's hardness is a measure of its relative resistance to scratching, measured by scratching the mineral against another substance of known hardness on the Mohs Hardness Scale.
Explanation: Hope this helped! :)
Basically taking water, and then making a different compound react with the water.