Dissolution and Solubility
Dissolution and solubility is how well something breaks apart and mixes into a liquid until it disappears.
When you stir sugar into warm water, the sugar breaks into tiny pieces. Those pieces spread out and mix into the water until you can't see them. Some things dissolve fast, like salt. Others, like sand, just sink and stay at the bottom.
Explaining dissolution and solubility by grade level
Drop a pill in warm water. It breaks into tiny bits. The bits mix in and seem to go away. Cold water makes this happen more slowly.
Projects that explore dissolution and solubility
A pill's ingredients affect how fast it breaks apart and mixes into warm water. Four lactase brands each dissolve at a different speed in water heated to 37 degrees Celsius on a magnetic stirrer. The Lactase Enzyme brand dissolves the fastest of the four.
The physical form of a solid affects how quickly it breaks apart and mixes into a surrounding liquid. Three decongestant brands dissolve in a dilute hydrochloric acid solution with enzymes added to match real stomach conditions, kept at around 37 degrees Celsius. A magnetic stirrer keeps the liquid moving at a steady pace while each tablet's dissolution time is recorded across five repeated trials.
The same chemical compound can break apart and mix into a liquid at different rates depending on its tablet form. Six pain reliever tablets — Advil, ibuprofen, Bayer, aspirin, Tylenol, and acetaminophen — each go into simulated stomach acid and distilled water heated to body temperature. A magnetic stirrer keeps the liquid moving at a steady rate, so dissolution speed reflects the tablet itself rather than uneven mixing. Across four repeated trials, all tablets dissolved faster in distilled water than in stomach acid. Bayer dissolved the fastest overall, and aspirin dissolved the slowest.
Substances already dissolved in water can change how well a new solid mixes in. Aspirin tablets go into three cups: plain water, sugar water, and corn flour water. As aspirin dissolves, it releases acid and lowers the pH. Every minute for five minutes, you check the pH of each cup. The plain water and sugar water show a steady drop at about the same rate. The corn flour water barely changes — meaning the starch slows how fast the aspirin breaks apart.
Hotter water lets more solid break apart and mix in. You measure 100 ml of water at 20 degrees Celsius and add sugar a little at a time until no more dissolves. Then you heat the water to 40 degrees and keep adding, repeating at 60, 80, and 100 degrees. The same test runs with salt and baking soda. All three substances dissolve more as the water gets hotter. Sugar shows the biggest jump, going from 240 grams at 20 degrees to 480 grams at 100 degrees.