MEASUREMENT OF QUANTITY OF MATTER D 



of the scale, or (#) by seeing if it swings an even distance on each 

 side of the centre ? Make an observation and explain the result. 



7. What kinds of matter should be used for standards in weighing 

 accurately ? What is the advantage of aluminium over platinum for 

 small standards ? Should weights be cleansed ? 



5. Measurement of Length and Volume. 1. Find out the 



length of a given object by seeing how many times a given 

 standard length is contained in it. Use 1 centimetre as a 

 standard. (1 centimetre is one-hundredth of a metre.) 



2. Measure the dimensions of a regular- shaped body. 

 Use 1 centimetre as a standard. 



3. Measure a given plane area by means of a body of 

 standard area, and also by calculation. Use a square centi- 

 metre as standard. A square centimetre is a square of which 

 the side is 1 centimetre. 



4. Find out by calculation how many times a given cube is 

 larger than a standard cube. Use as standard a cube of which 

 the side is 1 centimetre. 



5. Find out by displacement of water, which readily 

 adapts itself to any shape, how many times a standard cube 

 is contained in an irregular-shaped body. Use a graduated 

 vessel, marking cubic centimetres. 



6. Verify the graduation of a burette by weighing the quan- 

 tities of mercury or water delivered into a weighed vessel. 

 Each division need not be tested. Care is needed in finding 

 when the middle point of the liquid surface is level with the 

 proper mark on the vessel. 



The above exercises show that the same methods are used 

 in comparing the lengths and volumes of various bodies as in 

 composing quantities of matter, and that there is the same 

 necessity for a standard length and a standard volume for 

 purposes of comparison. 



Precautions in Measuring. The distance between any 

 two points is found by measuring the number of units of 

 length in the imaginary straight line joining them. In 

 measuring any given distance we have to depend on our eye- 

 sight or touch for ascertaining the coincidence of two points 

 or marks.- Care must be taken that this coincidence is real. 



