wunder beta🧪 Chemical Reactions
Bonds break, atoms rearrange, energy flows: the chemistry behind change.
What you’ll learn
- Explain reactants, products, and how conservation of mass requires balanced equations.Reactions rearrange atoms from reactants into products with new properties. Conservation of mass, from Lavoisier, means no atoms are lost, which is why equations must be balanced with equal atoms on each side.
- Distinguish exothermic and endothermic reactions and explain activation energy.Breaking bonds costs energy and forming them releases it. Exothermic reactions give off net energy; endothermic ones absorb it. Activation energy is the initial barrier every reaction must overcome to begin.
- Classify reaction types and identify factors that control reaction rate.Reactions fall into types like synthesis, decomposition, replacement, and combustion. Rate depends on temperature, concentration, surface area, and catalysts, including enzymes that make biological reactions fast enough for life.
Questions this course answers
In a chemical reaction, the starting substances are called:
Reactants are the starting materials that transform into products.
The law of conservation of mass states that in a reaction:
Atoms are conserved; they rearrange but are never created or destroyed, so total mass stays constant.
Why must chemical equations be balanced?
Balancing ensures each type of atom appears in equal numbers on both sides, honoring conservation of mass.
An exothermic reaction is one that:
Exothermic reactions release more energy than they absorb, giving off heat or light.
An instant cold pack works because dissolving a salt is:
The endothermic process absorbs heat from the surroundings, making the pack feel cold.
The minimum energy needed to start a reaction is called the:
Activation energy is the initial energy barrier molecules must overcome to react.
Grounded in trusted sources
- Britannica, 'Chemical reaction' (britannica.com/science/chemical-reaction)
- American Chemical Society, Energy Foundations for High School Chemistry (highschoolenergy.acs.org)
- Chemistry LibreTexts, 'Exothermic and Endothermic Reactions' (chem.libretexts.org)
- Atkins, Peter and Jones, Loretta, 'Chemical Principles' (W. H. Freeman, 2016)
Every Wunder lesson is built from real, reputable sources — never invented.
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