In science today (10/28/13) we did 2 demos, one about whether ice would float/sink in water, oil and alcohol and the other was how much would the balls of liquid rise/sink when the temperature was lowered/raised, and we learned how to make quality qualitative observations.
On the first demo, we started with the pouring of the liquids. We poured 10mL of water (purple), 10mL of oil (yellow), and around 5mL of alcohol (red). Then we poured each into the beaker in the order that I listed them, but they got all mixed up. The oil bubbled on one side and the water and the alcohol merged. Luckily Mr. Pro had a beaker with the liquids separated so we could do the test. So before he dipped the ice we made a (sort of) prediction by looking up the density of ice on Google and we got a number around 9.3. So we predicted that it would float on water but sink in alcohol and oil. But when we performed the experiment, “the moment of truth” in Mr. Pros words, the ice floated on oil and water but sank under the alcohol. And what was cooler still was that as the ice melted, it formed bubbles inside the oil that when came to the bottom of the layer, they stayed there as if it were solid ground! It was really awesome, but we were still confused at why it floated on oil of its density was higher. Then we actually did the measurements (manually this time) and got different results then that Google link.
Meanwhile all that commotion in the class, Mr. Pro had left a Galileo thermometer in the fridge. For those of you who don't know what a Galileo thermometer is, it’s a glass tube filled with water, and in that water are different liquids with different densities inside little glass bulbs. We can measure the temperature by observing these liquids' behaviors as the temperature is lowered/raised. Since it was lowered, the lowermost liquids travelled up and stayed there until the temperature rose and they sunk. These probably can’t give us an exact measurement since there are no measurements on the side on the glass tube, but we can use it to know if it’s really hot/cold out.
Next we learned how to make deductions from qualitative observations. We took our observations from the demo with the dry ice a class or two ago and made deductions on what the observations meant. A deduction (in this case) is basically an explanation of why something happened. Our experiments were:
1. look at the ice
2. touch it
3. press the flat part of the knife on it
4. push it across the tray
5. breathe on it
6. put in a jar with water and a cork seal
7. put the ice in the water
8. put a graduated cylinder full of water upside down on the ice
For the first one, the observation was that the ice was subliming(#9)
For the second, it was that it felt really cold, numbed your finger for a short time, and in extreme cases, (no one was brave enough to try), frostbite
For the third it was that it made a high pitched noise, cooled down at an extremely fast rate and water froze on the parts of the knife nearest to the ice
For the 4th it was that the ice moved without slowing down too much
I’m going to let you guess for the next ones to see how much you really paid attention in class!
Overall, this was a really entertaining lesson and we learned a lot about the densities of different objects/liquids that we didn't know about before, and we learned that the Galileo thermometer's glass bulbs of liquid rise when it gets cold, unlike regular thermometers (or at least, that's what I got from that demo).