MEASUREMENT OF QUANTITY OF MATTER 7 



6. Relative Quantities of Matter in Equal Volumes of 

 Different Substances. 1. Compare the quantities of matter 

 in equal volumes of mercury and water, and turpentine. Use 

 a marked beaker or flask, and a balance. 



2. Compare the volumes of the above substances when 

 equal quantities of matter are taken in each case. Use a 

 beaker for weighing, and ascertain the volumes by pouring 

 into a graduated vessel. Commence with the turpentine. 

 , 3. Compare the volumes contained in equal quantities of 

 brass and water. The volume of a piece of brass is equal to 

 that of the water it displaces, and, by the displacement of water 

 in a graduated vessel, the volume of the brass is easily measured. 



4. Taking as unit the quantity of matter contained in a 

 given volume of water, calculate the numbers to be given to 

 equal volumes of other liquids and solids. Refer to the table 

 of densities. 



The above exercises show that the appearance and size of 

 a body give no exact information as to the quantity of matter 

 it contains. Bodies vary in density. In order to ascertain 

 the density of a body the volume and quantity of matter are 

 each measured. The volume of a liquid is easily measured as 

 it adapts itself to any required shape, but the volume of an 

 irregular- shaped solid is less easy. It may be measured by 

 displacement of a suitable liquid in a graduated vessel. It is 

 a great convenience to compare all substances by reference to 

 a common standard, and water of a fixed density is selected. 

 Then the numbers, called specific gravities, which tell how 

 much denser various substances are than water, show their 

 densities relatively to one another. But it is more systematic 

 to express the density of a body by the number of units of 

 mass in unit of volume. A body which has four units of mass 

 in unit of volume is twice as dense as one containing two 

 units of mass in unit of volume, and so on. 



It must be remembered, when we speak of equal quantities 

 of different kinds of matter, that we do not refer to equal 

 volumes, but to such volumes as contain what we have agreed 

 to call equal quantities of matter. Later on we shall add to 

 our knowledge of equal quantities of matter. 



