64 Domestic Science 



the mass of 1 c.c. of each material is practically the 

 same for both examples and is evidently independent 

 of the size and shape of the particular body dealt with. 

 A corresponding statement to this will still hold good 

 if our measurements of volume and weight are expressed 

 in different units, e.g. cubic inches and ounces, or cubic 

 feet and kilograms. 



Thus, if our three figures were made of wood, iron, 

 and lead as suggested, our results will be something 

 like this : 



1 c.c. of lead has a mass of 11*2 g. 

 iron 7-8 g. 



wood 0-70 g. 



If our measurements be made in cubic inches and 

 ounces, we shall have : 



1 cu. in. of lead has a mass of 6*47 oz. 

 ,, iron ,, 4'51 oz. 



,, wood * 0*404 oz. 



In cubic feet and kilograms we should obtain : 

 1 cu. ft. of lead has a mass of 317 Kg. 

 iron 221 Kg. 



wood 19-8 Kg. 



To denote the mass of unit volume of a substance 

 the name " density " is used. Thus the density of 

 lead may be variously stated as 1T2 g. per c.c., 6*47 oz. 

 per cu. in., or 317 Kg. per cu. ft. In each case the units 

 of mass and of volume must be clearly stated and it 

 will be noted that the numerical portion of the state- 

 ment varies with each choice of units made. 



Exercise for Student. 

 Determine by calculation 



(a) The density of lead in grams per cu. dm. 

 (6) iron in kilograms per c.c. 



(c) wood in Ib. per cu. yd. 



