A beta particle, also called beta ray or beta radiation (symbol β), is a high-energy, high-speed electron or positron emitted by the radioactive decay of an atomic nucleus during the process of beta decay. There are two forms of beta decay, β− decay and β+ decay, which produce electrons and positrons respectively.
To identify which liquid is water you need to be able to test different ways with the different substances and see which liquid acts more like water. Sense of smell, water has a specific scent smell the substances and you’ll get closer to figuring out which is water
You have to convert the mass from g to kg since the unites for a joule is kgm²/s². When you do this you should have E=(1.0×10⁻⁷ kg)×(3.00×10⁸ m/s)². With that E=9.00×10⁹J which equals 9.00×10⁶kJ.
I hope this helps. Let me know if anything is unclear.