The difference in composition between a weak base and its conjugate acid is

A weak Bronsted-Lowry base is a weak proton acceptor, where the proton is in the form of H+, so the conjugate acid formed contains one more H atom and an extra positive charge.
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1A: The legs can be a adjusted, as well as the sand can be swapped out. It’s a very good design for running multiple tests.
1B: He could add books or something under the front or back legs in order to increase/decrease the incline, therefore imitating the hypothesis.
1C: He can change out the sand grains to finer ones, or coarser ones, and record his results of each test.
2: If he sets the model at a steep incline and tests it with coarse sand and fine sand, seeing which one makes a narrower, deeper hole.