燃燒係咪會令元素COMBINE成COMPOUND?

當氫燃燒時, 與氧結合成為水. 2H2 + O2-------> 2H20+能量 此化學作用是比出能量, 此為exothermic reaction, 此能量為光與熱. 所以看到火(即光與熱). 在reaction未開始時, you need to ignite the hygrogen, than the reaction starts the chain reaction which supplies enough energy to complete the combination of 2 hydrogen molecules to react with 1 oxgen molecule to form 1 water molecule, together with flame & heat.

since hydrogen and oxygen are highly flammable so dont use any ignition source to try to turn them into water!!
u can increase the pressure in Le Châtelier's principle increasing pressure can also favour a forward reactions

All reactions involve an energy, called activation energy, before any reaction occurs.This energy can be used to break the bonds in reactants, or remove electrons in the reactants, so as to force the reaction to occur. Different reactions require different amounts of activation energy. If the reactants of a reaction cannot gain enough energy, no reaction will occur.
In your case, at room temperature, there is not enough energy from the surrounding environment supplying for breaking bonds in the reactants( Hydrogen and oxygen), ie, there is not enough activation energy, so no water is formed.
Igniting the test tube of hydogen is necessary to provide enough activation energy to hydrogen and oxygen, and hence to force them to form water. There are several ways to provide enough activation energy in the case, for example, applying electricity, but not just applying heat energy in fire.
Actually, you can write "+ heat" or add an triangle under the arrow in the equation to indicate, but this is optional and not a must.