9.13.2010

Today in class we took the quiz that was supposed to be on Friday but, was switched to today. If you did not take the quiz you can make it up in the test center. After taking the test we went over it shortly and did not have time to go to the writing lab like was planned.

Friday September 10, 2010

Today in class we started off my going over unit conversions on page 11. A problem that we did in class was this, If a glacier flows at a rate of 32.5 feet per year, what is its speed in cm per hour?

1.To start to solve this problem you must put 32.5ft over one year.

2.Then multiply this by 12in over 1 ft and then the feet cancel out.

3.Next multiply 2.54cm over 1in and then the inches cancel out.

4.Then multiply 1year over 365 days, the year will cancel out with the year from the first step of the problem.

5 And finally you multiply 1 day over 24 hours, but to get the answer you have to multiply all the numbers on top and then divide by all of the numbers on the bottom. Once you do that you get .113 and thats your answer.

After we went over conversions, Mr. Paek showed us how to get on Web assign, which is the homework. To get to Web assign go to your moodle account. From there go to chemistry with Mr. Paek, and then press on the Web Assign Link. A quicker way to get there is to just go to Webassign.com. Once you get to Web Assign you sign in. It will say institution and there you put glenbrooksouth.il then your password AND your username will be your id number. Once you get into web assign there are a number of assignments that are all due the day before the test. Most of them we have already learned but some of them we haven't. F0r the web assigns the questions that have more then 2 answers, you get only 2 guesses on. And for the questions with only 2 answers you only have one guess. Once you are done with an assignment you press submit and it will tell you all the questions you got right. During class we went to the computer lab and worked on web assigns for the rest of the period.

Wednesday September 8, 2010

Today in class, we finished our labs working on density that we started yesterday. Next, Mr. Paek showed us a demo by using gas, a special type of soap, and a long stick with fire on the end. He had a volunteer shake and pinch on the tube from where the gas was coming from in order to make the soap from inside the beaker rise into the air as a bubble. Once it did, he poked the stick on fire at the rising bubble and a big burst of flames came from the air.

After the demo, Mr. Paek reviewed with us about finding the density of certain objects, and the ntaught us about using Unit Analysis. This means that the units in the numerator and the denominator cancel out so then another unit used will replace its spot. For example, if we are trying to figure out the number of seconds in 1 day, then we would write out the equation like this: 1 day/1 x 24 hrs/1 day x 60 min/ 1 hr x 60 sec/ 1 min = 24 x 60 x 60= 86,400 sec in 1 day. This works because the units day, hrs, and min cancel out which leave sec as the remaining unit for the final answer.

Since we didn't do so well on the last section of the quiz we took last week, we have a quiz on friday covering the same material. So our only homework for tonight is to study measuring the volume of water in graduated cylinders and note cards, and make sure you make 1 guess.

Tuesday 9.7.10

Today in class, we started off by going over the basics of density (the formula and units of density). The formula for density is . In order to find mass and volume we need to know the units of mass (grams (g), kilograms (kg), and milligrams (mg)) and volume (milliliters (mL), Liters (L) and cm (cubed)). We followed this up with examples of finding density to get a better understanding for the material (Ex: If the mass of a powdered substance is 6.52 kg and the volume is 22.4 L, what is the density? You would then go on to put the mass (6.52kg) over (divide by) volume (22.4 L) and get 6.52kg/22.4L= .291 kg/L, and because it is multiplication, the answer has to match the lowest amount of significant figures, in this case, 3).

We also did an example of the different densities of substances in water and found out the a substance with higher density than all the rest sinks down to the bottom and the substance with less density than all the rest, floats to the top. All the substances in between then order themselves from top to bottom going from least dense to most dense in a totem pole looking fashion. We finished up class with a Density lab. For this lab we needed a regular object, an irregular object, a ruler, a balance and a 10 mL and 100 mL graduated cylinder.

In this lab we found the mass of a regular solid object (a metal rectangular prism) using the balance to "mass" it and the volume using the formula of Length x Width x Height. We then used these measurements to calculate the density of the solid using the equation .

To then find the density of an irregular solid object (a metal nail) we measured the mass using a balance. To get the volume we filled a 100mL graduated cylinder about half full of water. Once we measured the exact volume of the water, we added the nail and then measured the volume again. To get the volume of the nail, we subtract the initial volume of the water from the volume of the water with the nail. Once we have the mass and volume we again use the formula to calculate the density.

Finally, we measured the density of a liquid. We first measured the mass of an empty 100 mL graduated cylinder. Once we got that measurement, we filled the cylinder about one third full. We then measure the mass of the cylinder plus the liquid and then subtract the cylinder's measurement to get the mass of the liquid. We then get the volume of the liquid simply by measuring it in the graduated cylinder. Once we have the mass and volume, we calculate the density one final time by using the formula .

Our homework for tonight, is to complete pg. 9 which Mr. Paek gave out at the beginning of class to go in our notebooks. This is simply just more examples of finding the different components of the density formula ().

Friday 9.3.10

Today we started the first few minutes of class making sure that everyone was able to access their blogger and google apps account (and as it turns out, mine works). We then proceeded to review the rules of significant numbers. The significant figure rules state that all non zero numbers are significant, zeroes between significant numbers are significant, any zero after a decimal is important, and that any zero used as a placeholder is not significant. After the short review we learned the rules to add, subtract, multiply, and divide using significant numbers. The rule for adding and subracting is that you round your answer to the same number of digits past the decimal point as the smallest number of digits past the decimal point. For multiplication and division, you round to the smallest amount of significant numbers. Finally we learned about scientific notation. When writing a number in scientific notation, you move the decimal until it is directly behind the first significant number and multiply it by 10 to the according power (for example 67,989,097 would be 6.7989097 times 10 to the seventh power). Unfortunatly however we were unable to get to a deminstration that involved fire.

Wednesday 9.1.10

Today during the first 30 minutes of class we finished our measurement lab by measuring five objects three of which had to be a jumbo paper clip, a piece of paper (the long way), and your height. The other two were students choice. We measured these in centimeters. The next step of the lab was to weigh the objects. This had to be done in grams. You had to weigh a jumbo paper clip, a piece of paper, and two objects of your choice. The final step of the lab was to measure the temperature. You had to find the room temperature, and then you had to do two different measures by filling up a beaker of water and finding its temperature.

          For the next 20 minutes of class we learned about the significant figure rule. The significant figure rule has four parts. 1. Digits other than zero are always significant. 2. Zeros between non-zero digits are always significant. 3. Any final zero after a decimal point is significant. Zeros used solely for spacing the decimal point (place holders) are not significant. We then filled out a little piece of paper based on how many significant figures were in each of the measurements. 

          On Friday we will be having a quiz on measurements. There was not any homework for tonight.

Tuesday 8.31.10

Today in class we took a few minutes to label all the important things in the room like the fire exits and water showers. Then we identified some materials. We identified a beaker, flask, Bunsen burner, a ring stand and a funnel.  We also talked about different types of measurements. To start off we got a ruler with a filled in a line on top. We had to estimate the length to the closest we can. With that you only have one guess. That means when you find your measurement it is not exact so you estimate to a reasonable length. When trying to find the measurement of a graduated cylinder, you measure from the lower dip in the water. Then we split into lab groups and started working on measurements. We took measurements in different ways. We found the smallest reading device for each utensil. The most accurate was a 10 ml graduated cylinder. It has the smallest reading device so it is most accurate. Some reading devices were 25 ml for a 400 ml beaker, 10 ml for 100ml beaker. 1 ml for 100 graduated cylinder and .2 ml for 10 ml graduated cylinder, which is the most accurate. After that we take a buret clamp and place a 250 ml beaker under it so it will catch the liquid. Fill the buret with water then open the valve and see how much water drains. The unique this about a buret is that the measurement starts at 100 then drops to 0. The reason for this is so you can see how much water or liquid you dropped or took out. We then recorded how much water was emptied out to the nearest 10nth. Then you let the water drain for 3 seconds and you record how much water drained. That is when we started cleaning up. This lab will be continued…