Team Up: Combination Reactions
See elements combine to form compounds.
What this lesson covers
Why it matters
Hydrogen and oxygen are invisible gases, but when they meet with a spark, they crash together to form water.
The idea in plain words
Balance check: confirm that 2 molecules of H2 and 1 molecule of O2 yield 2 molecules of H2O.
Predict first
What happens when hydrogen and oxygen react?
In a combination reaction, two or more substances join to form a single new product.
- They mix to form a new gas called hydroxide
- They combine to form water — correct
- They repel each other and stay separate
What you do
Ignite the mixture. Listen for the pop and watch the steam form.
Check yourself
Why is this reaction classified as a combination reaction?
Combination reactions are defined by multiple reactants joining to create a single product: A + B → AB.
What is the correct balanced equation for this reaction?
Hydrogen and oxygen combine to form water, so the correct balanced equation is 2H₂ + O₂ → 2H₂O. H₂ + O₂ → H₂O₂ is balanced too, but it gives hydrogen peroxide — the wrong product.
What observation confirms the reaction occurred?
Hydrogen burns explosively with oxygen, producing a characteristic pop sound.
- Because it produces heat
- Because two reactants form one product — correct
- Because the reactants are gases
- H₂ + O₂ → H₂O₂
- 2H₂ + O₂ → 2H₂O — correct
- H₂ + O → H₂O
- A loud pop sound — correct
- The gas turns blue
- Silent mixing