Question

what are the units of concentration?
our goal is to measure the concentration of contaminants in the flint water source. so far, we know two things:
the more solute that is present in a particular amount of solution, the more concentrated that solution will be.
the flint water source seems to have high levels of solutes such as lead and copper.
but how can we measure \how high\ the concentration of a substance is?
on the surface, measuring concentration should be simple. just count how many particles of solute are present in a particular amount of liquid. lets say both of these samples are 1 ml

Explanation:

Step1: Count particles in less concentrated

Count the number of pink particles in the "LESS CONCENTRATED" circle.
There are 5 particles.

Step2: Count particles in more concentrated

Count the number of pink particles in the "MORE CONCENTRATED" circle.
There are 13 particles.

Answer:

LESS CONCENTRATED: 5 particles; MORE CONCENTRATED: 13 particles