A learner has to mix a strong acid with water in a school laboratory. Which order is the safe one?

1. Mixing a strong acid with water releases heat, and heat released too quickly can throw the liquid out of the container. 2. The laboratory rule is fixed: never add water to acid, and always add the acid to water. 3. Pouring water onto acid puts a small mass of water onto a large mass of acid, so the heat is released into a tiny volume. 4. Adding both at once, or adding ice first, gives no control at all over how fast that heat appears. _Source: Siyavula Physical Sciences Grade 12 (Everything Science, CC BY 4.0), Chapter 1: Skills for science_