An exothermic reaction releases heat. An endothermic reaction absorbs heat. Burning gas releases heat so it would be exothermic. Acid and water react heating the beaker would be exothermic because it releases heat from the reaction. Hope this helps! ;)
1.one substance must dissolve another : the solvent breaks the the solute causing it to dissociate into the solvent it can be both solids or gases that dissolve in the solute
2.the melting point will be higher than 100 degrees as the salt causes the solution to gain a higher melting point
3.either released or absorbed : energy is required to dissolve the solute but the solute may also release energy
4.the salt dissolved most quickly in the warm water : as there is more energy for the solute to dissolve
hope that helps
Reichsteins substance if I remember correctly.
Hope this helped! :)
- Juju