Lab 3--metric review

In today's lab the students are measuring various objects--a lab table, a metal box, a floor tile, an open door, etc. I am finding out if they remember how to measure correctly and to round to the nearest millimeter. Not a tough lab at all. Students are not terribly happy that I assign their groups, but it is such a better method than letting them choose their own. They focus better and ultimately learn more.

Sweet justice.

Day 4--Unit 2

Today was another density/sig fig day. We began going over homework, taking notes about how density is calculated. Density = mass/volume, with the units of g/ml for liquids and g/cc for solids. Water's density is 1.0 g/ml. You can find out if an object is less dense or more dense than water by placing the object into water. If it floats, it is less dense. If it sinks, it is more dense. We dropped bouncy balls and homies into the water and watched the magic.

Next we moved on to calculating with sig figs. When you add or subtract, you round the answer to the same place value of whichever of your numbers has less places. When you multiply or divide, you round to the sig figs of whichever number has the fewest. Watch this video to help you better understand, and also to blow your mind.



Sweet justice.

Day 3--Unit 2

Today we played a density game. First, I got several boys up in the room and gave them different color spheres which were all the same size but different masses. I had them line up from least dense to most dense and then timed them. Next the girls went and we compared times. Each section had different results. Next I gave them cylinders with the same mass but different sizes--harder! Same rules for lining up (in both cases a mistake cost five seconds). Finally, the last challenge used five objects but I gave them no heads up--which section could go the fastest? The S section had a group go in 15 seconds, the O section in 16, and the L section in 17. Very commendable results.

Following this we worked on sig figs again. Sig figs are important when you measure and use calculations based on your measurements. The rule of thumb is that your answer can't have more sig figs than the term you use that has the least. Complicated? The students are amazing me with how well they pick this up.

Sweet justice.

Day 2--Unit 2

Well, well, well, another exciting day in science class. We discussed our homework, which included the concept of mass and weight--what is the difference? The difference is that weight is the force of gravity acting on mass. Your weight can change, but your mass remains the same regardless of where you go. We also discussed volume measurements, noting that cubic centimeters (cc) are used for solid volume while milliliters (ml) are used for liquid volume. One cc is equal to one ml.

We next started learning about significant figures (sig figs) by watching the worlds greatest sig fig video. Here it is for your viewing pleasure:



Enjoy!

Sweet justice.

Unit 2--Day 1

Today we started unit 2 on the properties of matter. I had assigned HW 1,2,3 from the study guide to be completed after the test prior to class. We went over this HW, which included three main concepts: the difference between a physical property and a chemical property, the difference between an element and a compound, and the difference between a mixture and a pure substance.

To show the physical vs chemical difference, we talked about a piece of paper--what are some properties of it? Color, bendability, weight, mass--these are physical because you don't have to change the substance to note them. The flammability of the paper is a chemical property, because as it burns, it becomes a new substance.

We looked briefly at the periodic chart and could see that hydrogen and oxygen are elements which water (H2O) is a compound which has vastly different properties than either H or O. We talked about ratios (2 parts H to 1 part O for water).

Next we discussed the difference between a heterogeneous mixture and a homogenous mixture. Milk is a great example of both. Homogenized milk is all one color--well mixed--while milk out of a cow is heterogeneous. I also showed students my six year old milk which I keep in a cabinet. Yuck. Salt water is a mixture because it can be separated by simple physical means--there is not a special formula for salt water as there is for salt or water alone. You can prove this with a simple distillation process (or simple evaporation).

Class ended with me burning magnesium in the fume hood to show a dynamic chemical change as it turns into magnesium oxide. Where does the oxygen come from?

Sweet justice.

Unit 1--Day 11

Today we took the test. I arranged for this to be an online test--all done in the media center, each student on a computer. The test shuffles the questions and answers, so there is little chance of peeking, but the best part is that the feedback for the test is immediate. Students know right away how they did. Overall, I was impressed. The average score was about 56 out of 71. This could go up if the students had all taken advantage of the fact that there were practice quizzes online which mimicked the format of the test itself.

So, unit 1 down, unit 2 on the properties of matter to come. Sweet justice.