Answer/Explanation:
Part 1 and 3: Test tube 4. The hot water and Acid added to the substance makes it much more reactive, which is the reason why the new substance is bubbling. Hot water allows the particles in a chemical reaction have enough force and more chances to go through actual reaction process. This also caused it to create the most bubbles.
Part 2 and 4: Test tube 1 had the least amount of chemical reactivity. Cold water slows down the amount of times a particle in the substance hits another. This reduces the chance of it reacting and the strength of it's reaction. Test tube 1 was also missing the citric acid. Since acids have low pH it is very reactive with other particles with substances that contain less than 8 valence electrons. Without the acid it doesn't have ad much urge to react with. The lower the pH the better reactivity.
