How do we measure mass of a substance?
To measure mass we use some weights. These weights are made of iron or brass blocks having a standard mass. In markets or grocer’s shops weights ranging from 5 g to 10 kg are used. In laboratories or gold shops weights used are smaller, ranging between 5 mg and 100 g.
We can use a common balance to measure the mass of an article. The article and the metal weights are placed on two opposite pans of the balance. The quantity of the articles or the quantity of the metal weights is adjusted until the balance earth bar stands still horizontally.
Thus we can determine the mass of an article by comparing it with the total mass of the metal weights.
We can prepare a simple balance on your own. Collect a wooden rod with even diameter. Make three circular grooves, at the middle and two opposite ends of it. Tie a strong thread at the middle groove and hang the rod so that it is perfectly horizontal. Now collect two plastic lids of jars having same size. Make three holes at equal distance along the edge of each lid, lie three threads of equal length at the three holes of the lid. Make a knot taking three free ends of the threads. Prepare another pan in the similar way. Now hang two pans at two ends of the wooden rod with the thread as shown in the figure. Your balance is now ready for use. We can measure the mass of small objects like an eraser, a pen cap or a marble with it., using some coins as weights.