Break Costs. Form Pays.

You'll learnthat breaking bonds costs energy and forming bonds releases it, so ΔH is break minus form.

Methane burns and your house gets warm. Almost everyone says the energy came from breaking the bonds in the fuel, and that sentence is exactly backwards. Breaking a bond always costs, forming one always pays, and ΔH is the difference between the two piles. Twelve short steps; press Next for each one.

12 STEPS · 6 QUICK CHECKS · ΔH ≈ Σ(bonds broken) − Σ(bonds formed) · v4

breaking costs · forming pays · the flame is the difference

Before you start

What you're looking at

Methane burning: the fuel and two oxygen molecules on the left of the arrow, carbon dioxide and two waters on the right.

The question

The room gets warm. Did that energy come out of the fuel's bonds?

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