What is a phase change? what two circumstances can cause a phase change to occur

What is the inability of an individual or a society to achieve a minimum standard of living known as ?

Johnny rode his bike to a friend's house 4 blocks down the street in his neighborhood. he immediately rode back home once he realized his friend was not able to play. what was his displacement for the total bike ride? how did you determine this? what could we use as a reference point to determine he was in motion during his bike ride? why can you use it as a reference point

What substance is the most acidic. lemon juice. tomato juice. sodium hydroxide. water