reactivity

Everyday

1. (science, chemistry) How easily and how strongly a substance takes part in chemical reactions: «Potassium has high reactivity.» tree →
2. (science, psychology) How strongly a person or body reacts to something, such as stress or an allergy trigger. tree →

In the lessons

In science lessons metals are put in a «reactivity series» from most reactive (potassium, sodium) to least (gold, platinum); this explains why gold does not rust and why sodium fizzes in water. Phrases: «reactivity series», «high reactivity», «low reactivity».

Examples

• Potassium is at the top of the reactivity series. tree →
• Gold has very low reactivity, so it stays shiny for centuries. tree →
• We tested the reactivity of metals in acid. tree →
• Sodium's high reactivity makes it fizz and dart about on water. tree →
• Iron's reactivity with water and air makes it rust. tree →
• Some children have high reactivity to pollen. tree →

Note

Uncountable. Adjective: reactive; opposite: unreactive (inert). A handy reactivity order: potassium, sodium, calcium, magnesium, aluminium, (carbon), zinc, iron, (hydrogen), copper, silver, gold. Safety: very reactive metals are handled only by teachers.