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Magnesium ribbon is a thin strip of metal. It burns to a white powder. The powder does not turn back into ribbon by itself.

Chapter 1 in your Class 10 book is Chemical Reactions and Equations. Let's write changes down in symbols.

What you will learn

• What a new substance means — reactants go in, products come out.
• From words to formulae — a word sentence, then a formula sentence.
• Balancing the count — every kind of atom must match on both sides.
• Many become one — combination joins reactants into one product.
• One becomes many — decomposition splits one substance.
• Somebody takes somebody else's place — one element for another, or partners swapped.
• Oxygen on the move — oxidation and reduction, in one event.
• Slow reactions, all around — corrosion and rancidity, and what slows them.
• Writing the swapped formulas — ions meet new partners. A solid may form.

Quick catch-up

These earlier lessons help. Open one first if a line ahead is hard to follow.

• Nothing is lost — mass before a change equals mass after.
• Writing the formula — swap two valencies, cut down, write the formula.
• Which atom is it — the proton count names the element.
• When something new turns up — test before and after a change.

One rule before every bench

Every bench here is a simulation. No bench heats, burns or mixes anything for real. Rust and rancid oil are records to read. They are never things to make.