If a sealed syringe that contains some gas is heated, in which direction will the syringe plunger move?
Have you got a blow up balloon handy?
Inflate the balloon at room temperature, and roughly measure its circumference by some means. Now place it in the freezer, and wait 20-30 minutes. When you take it out, is it larger or smaller than the original measurement? Enquiring minds want to know the answer.
Is this scenario equivalent to the syringe? I'm pretty sure it is. How do we account for this macroscopic change?