How would you respond to a friend’s claim that chemists don’t know what to expect when synthesizing new materials?

You would most likely have to agree with the friend as scientists only know things by experimenting the unknown. So when synthesizing the new, the result will also be new and unheard of previously by the scientists.

i don't see a text, but i am gonna assume this *orbit* the curved path, usually elliptical, described by a planet, satellite, spaceship, etc., around a celestial body, as the sun.

o conteúdo de calor de um sistema é igual à entalpia apenas para um sistema que é constante