Helping young kids comprehend the three basic states of matter is an important part of building a solid foundation for the more complex physical science lessons.
This video goes over the states of matter and about reversible and irreversible changes between them.
This video satisfies the 2-PS1-4 requirement for second grade proficiency.
Students who demonstrate understanding can:
2-PS1-4. Construct an argument with evidence that some changes caused by heating or cooling can be reversed and some cannot.