The Chemistry of Cold
📖 The Chemistry of Cold
Endothermic reactions are like ice packs — they absorb heat! Think "enter" — energy ENTERS the reaction from the surroundings. That's why your hands feel colder, the test tube gets cold, or the beaker frosts up. The products have MORE energy than the reactants — they've absorbed that extra energy from you!
Chemistry glossary
- What is an endothermic reaction?
- A reaction that absorbs/takes in energy from the surroundings
In any chemical reaction, bonds in the reactants must be broken (requiring energy input) and new bonds are formed in the products (releasing energy). In an endothermic reaction, the energy needed to break the bonds in the reactants is GREATER than the energy released when new bonds form in the products.
Earn the mark scheme marks
🧠 Memory Aids
ENDO = IN = energy goes IN from surroundings = temperature goes DOWN
The "endo" prefix means "inside" or "within". Energy enters the chemical system from the surroundings, cooling them down. Cold packs, photosynthesis, and dissolving ammonium nitrate all pull heat IN.
ΔH sign rule: ENDO = ENTERS = positive — positive energy change means energy is gained by the system
Endothermic → ΔH is POSITIVE (the system gains energy, so the change is positive)
On the energy profile: "ENDothermic ENDS higher — the products are higher up on the diagram than the reactants."
Exo vs Endo summary: "EXO = EXit (out, hot), ENDO = ENter (in, cold)"
Now try it yourself
Quiz · Question 1 of 20
In an endothermic reaction, energy is:
Tap an answer to check it