Buoyancy test: checking drinks for sugar

It's no se­cret that car­bon­at­ed drinks can con­tain loads of sug­ar. We can use this prop­er­ty to per­form a cool den­si­ty ex­per­i­ment!

Safe­ty pre­cau­tions

None.

Equip­ment

• deep glass con­tain­er with wa­ter (such as an aquar­i­um);
• var­i­ous cans of reg­u­lar and sug­ar-free so­das (12 fl oz / 330 mL).

Step-by-step in­struc­tions

Im­merse var­i­ous soda cans in wa­ter. Note that the so­das with re­duced or no sug­ar don't sink!

Process de­scrip­tion

The cans them­selves are equal in size and con­tain equiv­a­lent amounts of liq­uid and gas; the cans’ dif­fer­ent buoy­an­cies are re­lat­ed to the den­si­ties of the drinks in­side them. Den­si­ty is a prop­er­ty that de­fines the mass of a cer­tain vol­ume of a giv­en sub­stance. A sub­stance’s den­si­ty de­pends on its com­po­si­tion. Drinks with­out sug­ar (con­tain­ing tiny quan­ti­ties of a sug­ar sub­sti­tute) or with re­duced sug­ar have a low­er den­si­ty than stan­dard so­das. As a re­sult, giv­en that the vol­ume is con­stant, the mass of the drink with the sug­ar sub­sti­tute is low­er than the mass of its sug­ary coun­ter­part. This al­lows the sug­ar-free drink to float even as its sug­ary com­pan­ion sinks.