Which 2 characteristics must and object have in order to be considered matter?

Atank contains 240 liters of fluid in which 10 grams of salt is dissolved. brine containing 1 gram of salt per liter is then pumped into the tank at a rate of 6 l/min; the well-mixed solution is pumped out at the same rate. find the number a(t) of grams of salt in the tank at time t.

Which compounds have the empirical formula ch2o? a.c2h4o2 b.c3h6o3 c.ch2o2 d.c5h10o5 e.c6h12o6

The excretory system,need answers for all: )