A law can be best described as any action or a relationship or a set of observations that are universally true and valid and are held to be right without any exceptions. For example Newton’s laws motion, Einstein’s Law of energy, etc.
A law is observed to be true under all conditions, so is accepted as a fact.
The statement: The volume of a gas increases as it is heated at constant pressure, can be best described as a law.
Basically, this statement is one of the gas laws. It is most frequently known as Charles’s Law. This can be written in other words as: Volume of any gas is directly proportional to its temperature at constant pressure. It is universally valid and true, thus is a Law.
The statement: sodium reacts with chlorine to form sodium chloride, is not a law. A law is a generalized fact but here are talking about a specific case.
The third statement: The universe is infinite in extent is a hypothesis not a law.
All livning organisms on Earth require water to survive their life. This statement is not laws since it is not based on observations and fact these are general hypotheses.
The burning of coal is causes global warming. Hence, this statement is not laws since it is not based on observations and fact these are general hypotheses.