When a helium balloon rises in the air, it expands. If the volume of the balloon doubles, what happens to the density of the helium inside it? a. The density decreases by half
b. The density doubles
c. The density triples
d. The density stays the same

Imagine that you have produced several versions of lactase, each of which differs from normal lactase by a single amino acid. describe a test that could indirectly determine which of the versions significantly alters the three-dimensional shape of the lactase protein.

Compare and contrast the bohr model and the electron cloud models of the atom.

Why are pipes bursting in the in extremely cold weather?