Nitrate ions 
and potassium ions 
.
<h3>Explanation</h3>
Potassium dichromate undergoes a double-decomposition reaction with barium nitrate to produce barium dichromate and potassium nitrate. The reaction is possible due to the low solubility of barium dichromate that precipitate out of the solution readily after its production.
Start with the balanced chemical equation for this process:
Rewrite the chemical equation as an ionic one; express all soluble salts- those with state symbol (aq)- as their constituting ions while leaving the insoluble (s) intact.
and 
are found on both sides of the equation by the same quantity. The two ions thus took no part in the net reaction and act as spectator ions.
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!
Answer:
a new substance is formed, if heat is formed, color change, the evolution of gas, and bubbles or fizzing
Answer:
The amount of thermal energy stored in an object depends on three things.
- The mass of the object.
- The temperature of the object.
- The amount of energy that the particular material stores per degree of temperature.
