This is an easy one to test. Just get an unopened can and weigh it on some digital kitchen scales that can measure milligrams. Record the weight. Open the can and weigh it again. What happened to the weight? Weigh the open can again after one hour, and then the next day. What is happening to the weight of the can?
A can of soft drink contains carbon dioxide gas to make it bubbly. That Shhh sound you hear when you open the can is the carbon dioxide gas escaping. Carbon dioxide is made up of the elements carbon and oxygen. These elements have a mass and therefore carbon dioxide has some weight – albeit not much. But now that weight has escaped the can and what you should see is that an open can of soft drink weighs less than the unopened can. The longer you leave it open, the more carbon dioxide will escape and the less it will weigh.
Check FLEET’s demonstration