Chemical compounds undergo both physical and chemical changes. which of the following is an example of a chemical change question 3 options: heating a solid material to a liquid form combining oxygen gas and hydrogen gas to form liquid water cooling a gas into its liquid form salt (nacl) being dissolved into water

Combining oxygen gas and hydrogen gas to form liquid water is a chemical change. Pretty sure the rest are physical changes because a chemical change happens when a substance is altered completely. A physical change is when a substance keeps its components (I dunno what word to use) but just changes into a diferent shape. At least thats how my teacher explained it to me.

They are like other investigations? say there was a murder u have to do blood test and finger prints which run through a lab. 

Ibelieve y y even though i've only taken chemistry for one year