Energy Changes: Bond energies.

Question 1

Why are exothermic energy changes shown as negative?

Answer 1

• Energy has been transferred from the chemicals.

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Question 2

Why are endothermic energy changes shown as positive?

Answer 2

• Energy has been gained.

Question 3

What are bond energies like?

Answer 3

• Breaking chemical bonds require energy (endothermic).
• Making bonds releases energy (Exothermic).
• Every chemical bond has an energy value.
• Tells us the energy required to break the bond.