Answer:
Place the experiments on a scale
Explanation:
If you place two of the same experiments on a scale, and cover one with a cup, the one with the cup will "lose" mass, while the other won't, due to the cup being a "containment field" I guess you could call it.
Answer:
hydrogen ions
Explanation:
Acids are substances that when dissolved in water release hydrogen ions, H+(aq). Bases are substances that react with and neutralise acids, producing water. When dissolved, bases release hydroxide ions, OH-(aq) into solution. Water is the product of an acid and base reacting.
Out of the three you gave ecosystem is what I would call the most broad. An ecosystem includes living AND non-living things in an area
Community is all the LIVING things in an area (plants are included and I think bacteria is too, but I'm not sure)
Population is pretty narrow it just looks at specific species in one area. Population of mosquitoes doesn't include butterflies, if only looks at mosquitoes
Hope this helped!