Hydrogen gas can combine with oxygen gas under certain conditions to form water.
which name is a general term for water in this reaction?
product
ionic compound
reactant
isotope

The correct answer is product.

Explanation:

Hydrogen gas reacts with oxygen gas to generate water molecule.

   2H2+O2 = 2H2O

We all know that that substances which are present at the left hand side of the equilibrium sign act as substrate and the substances those are present in the right hand side of the equilibrium sign are called products.

  From that point of view it can be stated that water or H2O is the product of the reaction between hydrogen and oxygen.

first one is the correct answer

answer : one can design an experiment using a liquid and an additive that can be added to the liquid and observe the chemical changes in the reaction species.

one would need a beaker which is filled with a known amount of the liquid in which thermometer is placed to measure the temperature changes; after addition of the additive to the liquid solution one can note down the temperature change and find whether the reaction is endothermic or exothermic in nature. by subtracting the initial temperature value with the final temperature one can find the temperature changes.

various combinations of liquid and additive can be used. liquid in this case can be a known quantity of water and additives can be epsom salt or without epsom salt the experiment can be conducted to notice the changes. water and ice, hydrogen peroxide and dry yeast, vinegar and baking soda,etc.