ENERGY 87 



spring from the muscular energy of the arm in pushing. 

 Not only may energy be transferred from one body to 

 another, but one kind of energy may be changed to a dif- 

 ferent kind either in the same body or in passing from 

 one to another. Thus, muscular 

 energy in the arm became elasticity 

 in the spring. 



Experiment 78. Into a strong test tube 

 put an inch or two of water. Find a stop- 

 per which exactly fits, so that it may move 

 up and down easily within the tube. Push 

 it down upon the water lightly. Now heat 

 the water slowly and with caution. As the 

 heating continues, what do you notice ? What sort of energy is 

 being used? What is its effect upon the water? Is energy 

 imparted to the water ? What is the proof of this ? 



Experiment 79. Put a piece of zinc into a test tube with 

 hydrochloric (muriatic) acid. Chemical action at once begins, 

 the zinc acting upon the acid. Feel of the tube from time to 

 time. Into what form of energy is the energy of chemical action 

 being transformed ? 



Many other experiments and common happenings 

 show that one form of energy may be changed into a 

 different form in the same or in another body. This 

 change of energy from one form to another is called 

 transformation of energy. The following principle is 

 generally believed by scientists : All forms of energy 

 are so related that any kind may be transformed into any 

 other kind. The study of these changes is an interest- 

 ing and important part of physics. 



99. Heat as a Source of Energy. The use of heat, as 

 a source of mechanical motion has become very common. 



