When matter changes a liquid is it a physical change

When a scientific theory has been tested and proved by the scientific community, it becomes a law

Which material burns faster? metal aluminum

Scientists often have to deal with numbers that are either very large or very small. for example, the radius of the sun is approximately 696,000 kilometers, while bacterial cells are as small as 1.9 × 10-4 millimeters. express each number in an alternate form.