Reactants are the elements or compounds before a reaction takes place. Reactants are found on the left-hand side of a chemical equation.

Products are the elements or compounds that are formed after a reaction has taken place.  Products are found on the right-hand side of a chemical equation.

A particle model of chemical reactions

Science

In the Understanding Chemical Reactions unit, pupils will build on their knowledge of atoms, elements, and compounds to learn about how atoms rearrange to form new substances during chemical reactions.

In the Solid, Liquid and Gas States and Changes of State unit, pupils learned to categorise substances and understand particle behaviour during changes of state.

This unit explores the basic atomic model, the differences between atoms, elements, and compounds, and the varying physical and chemical properties of elements. It covers chemical symbols, formulae, SI units, and IUPAC nomenclature, emphasising their use in describing elements and compounds.

Atoms, elements and compounds

substances present before a chemical reaction has taken place.

substances formed after a chemical reaction has taken place.

In a chemical reaction, what happens to the atoms?

In the chemical equation 2H₂ + O₂ → 2H₂O, what are the reactants?

Which of the following is a characteristic of a chemical reaction?

Not enough information is known, so it cannot be determined.

Different reaction conditions would lead to different answers.

After the reaction 2H₂ + O₂ → 2H₂O, what happens to the total number of atoms?

In the equation 2Na + Cl₂ → 2NaCl, what is the simplest ratio of sodium (Na) atoms to chlorine (Cl) atoms in the reactants?

A metal sulfate contains the group of elements -SO₄, nitrates have the group -NO₃ and {{}} have the group -CO₃.

What elements are present in the calcium chloride?

What of the following is an example of a molecular element?

Match the reacting elements with the compound formed.

What indicates a compound in a chemical formula?

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