What is phase change? How does matter change in phase?

Answer ASAP pls :(

Harvey kept a balloon with a volume of 348 milliliters at 25.0˚c inside a freezer for a night.  when he took it out, its new volume was 322 milliliters, but its pressure was the same.  if the final temperature of the balloon is the same as the freezer’s, what is the temperature of the freezer? the temperature of the freezer is  kelvins.

Why doesn't heat added to water make the tempature rise above 100c

Name the element in group 17, period 2. (periodic table)