Roads often have to be repaved because they crack over time. sometimes this cracking is due to the fact that the roads (as well as other objects) have a tendency to expand when heated and contract when cooled. thermal expansion and contraction are examples of
a.
physical and chemical changes.
b.
physical changes.
c.
chemical changes.
d.
neither physical nor chemical changes.

The lid of a pressure cooker forms a nearly airtight seal. steam builds up pressure and increases temperature within the pressure cooker so that food cooks faster than it does in an ordinary pot. the system is defined as the pressure cooker and the water and steam within it. if 2.0 g of water is sealed in a pressure cooker and then vaporized by heating, and 5655 j must be added as heat to completely vaporize the water, what is the change in the system’s internal energy? answer in units of j.