Ben and Sam were conducting experiments on physical and chemical changes in science class. First they added some salt to water and stirred it up until the salt dissolved. "That's a physical change" Ben said. "And that's a solution which is a mixture", added Sam. Next they added an anti-acid tablet to some water. The water began to fizz and bubble. The beaker got cooler. "That's a physical change too," Ben noted. "No, it's not," responded Sam. Who is correct and where should the contents of the beaker be placed in the Venn diagram?