Just saw your request regarding answering this so here it is:
All of them belong of Group 1 in periodic table and thus are highly reactive! Pattern of reactivity for Group 1 (Alkali metals) increases as you move down the group as their radius keeps increasing and thus electrons can be easily lost. Thus, to ID the lumps, Sheena should look at their reactivity and she should get the following trend:
When particles that attract each other come together, energy is usually released. The combination of the two particles is expected to result in a lower energy system. This lower energy system will be more stable than the different individual particles.
Hence, as this lower energy system is formed, the excess energy originally possessed by the particles is evolved hence energy is released when particles that attract each other are allowed to come together.
