The North Pacific DORC Expedition Blog for Kids: Calibrated Eyeballs

Hey guys,

Today we have been at the same station all day which has given us time to catch up with some experiments in the lab! In one of our experiments, we have to add a certain amount of a chemical reagent to a certain amount of seawater. To add another level, we also have to know how much seawater is left after each experiment so that we can use the same water. That wouldn't be too hard if we had a beaker with marks on it, but ours is a special jacketed beaker (water circulates through the outside to keep a constant temperature) and it doesn't have any marks! So we had to make our own. Leanne measured out 50 milliliters of water and poured it in to our beaker, and I used a sharpie to mark the level of the water. Then she added 50 more milliliters and I added another mark. I then measured the distance between the two marks and used that to make the next mark until we reached 600 milliliters. But later on when we were ready to start our experiment, Professor Bill measured out 200 milliliters and poured it in the marked beaker and it didn't reach the 200 milliliter mark!!! So instead of redoing the marks on the beaker (they were sharpie), we calibrated our eyeballs. In order to do this we found the distance from the beaker we had to stand for the water level to look like it was at 200 milliliters. But since we are all different heights, we had different spots, and I marked them with a piece of tape. That way, when we stand on our personal tape mark we will be able to tell how much water is in the beaker. You might be wondering why we had to do this if Leanne and I measured out the water. In a perfect world, that would have worked. However, we assumed that the beaker was the same size on the inside all the way up, which may not be the case. Also, it was a fun exercise!