If and when clauses are used to talk about causes and results that are usually true or factual. They use the present simple tense in both clauses, such as "if you heat ice cream, it melts" or "when it rains, the grass grows." Some examples provided are "if you cook an egg in the microwave, it explodes," "when you put water in the freezer, it becomes ice," and "if you eat too much chocolate, you gain weight."