 Okay, so we're going to do one of these review problems for chapter one. So we're going to look at a number that was given to us as a measurement, or that we got as a measurement in the lab, and we're going to determine some things about it. So how many significant figures it has in it? How many certain digits? How many uncertain digits? And what are the units? Okay, is everybody okay with doing that type of stuff? So, can anybody tell me any of these things already? One uncertain. Okay, one uncertain, right? Okay, one uncertain. Why would we say one uncertain? There's always only one uncertain digit in a measurement, okay? So, which digit is it? Is it the zero over the five? Five. The five is the uncertain digit, right? The five is the uncertain. Let's talk about that zero. So, is that zero? What is that zero? Leading zero, so it's one. Yeah, it's insignificant, right? So, all leading zeros, leading zero. Okay, then. So, how many certain digits do we have in this thing? Zero. Zero certain digits. Okay, so this is kind of a tricky question. Okay, and can we figure out the number of significant figures in this one? One. One, right? Because remember we came up with that little equation that said so, significant figures equals your certain digits plus your uncertain digits. And let's just make sure we did that correctly. So, if we put in our number of certain digits, zero, and we add that to our uncertain digits, one, right? What do we get? Zero plus one equals one, right? So, we did that correctly, because everybody said that. And the units. What are the units? So, milliliters, right? So, milliliters. So, capital L. And that's a SI unit or no? SI, yeah, so metric system, right? Okay, any questions on this particular problem? So, this is a good one to go over, like, leading zeros in, you know, very small numbers of measurement.