Density

During class today we:

• Checked in homework
• Went over Density Notes
• Got Density Homework

Density is D = m/v or Density = Mass/Volume. To solve a density problem such as the the example in the notes you first substitute what you know into the density equation. In this case, the chocolate bar has a mass of 55.6g and a volume of 30cm^3(Cubed). So start by substituting the mass and volume, D = 55.6g/30cm^3. You then simply just divide the two by using your calculator. When entered into your calculator you get, 1.8533333. According to the significant figure rule for multiplying or dividing you round to 3 sig figs. You then get 1.85g/cm^3.

Some other questions might give you the density and ask you for something else. In this case use simple algebra to solve. An example of this can also be found on the notes. This example states that that silver has a density of 10.5g/cm^3, it also states it has a mass of 25g and asks you to find the volume. First, set up your equation, 10.5g/cm^3 = 25g/v. To figure out the volume solve for v. To do this first multiply both sides by v. You then get 10.5v = 25. Then simply divide by 10.5. You get 2.380952.... round to 3 sig figs. Finally you get, 2.38cm^3.

The notes sheet and the homework for tonight can be found on moodle.

Density WILL be on the quiz tomorrow so be ready.

HW: Density sheet, study for quiz tomorrow.

The next scribe will be Jake A.

Unit 1: Precision and Accuracy of Measurements

Today we:

• Talked about the differences between Precision and Accuracy
• Handed back Quiz #1
• Received homework sheet on the Metric System
• Took notes on Precision, Accuracy, Measurements, and the Metric system.

To demonstrate how Precision and Accuracy contrast, we held an in-class competition based on the aim of the competitors. The more precise and accurate you were, the better you would perform.

Precision- how reproducible your value is

Accuracy- how close the measurement is to what it actually should be

Measurements- Use the metric system (Mass in grams, Length in meters, Volume in liters)

The Metric System- The following prefixes are used. Focus on 10^6 - 10^-12, specifically 10^3, 10^-2, and 10^-3.

HW: Metrics Sheet

Tomorrow's Scribe is Cody D

Day 6: Atoms and Paperclips

                  In class today we learned about pure substances and mixtures. We made a graph in class and i think it helped me understand this kind of stuff so im going to recreate it down below.

                                                                              Matter

                                                  _________________|__________________             

                                                  |                                                                       |

                                 Pure Substances:                                                        Mixture:

                    A substance that's smallest pieces                             Different types of atoms or 

                           are the same. Can be:                                        molecules that are physically 

                        Monatomic- single atoms                                         mixed together, but are not 

                Diatomic- atoms boned in groups of 2                                 chemically bonded.

             Polyatomic- atoms bonded in groups of 3+                            ________| _________

                        ____________| ____________                                  |                                   | 

                        |                                                |                        Homogeneous:           Heterogeneous:                         

                Elements:                               Compounds:             A mixture that has      A mixture that has 

          A substance that                    two different types           the same makeup.    the same makeup, but

         contains only one                   of atoms present in                                               can have different

             type of atoms.                     the same molecule.                                                     amounts.           

             ______|______                                     |                                                                                                   

             |                        |                             molecules:          

       Atoms:            Molecules:             Two or more atoms that

   the smallest        two or more             are chemically joined  

  basic unit of       atoms that are           together. Can be more 

   a chemical       chemically joined       than one kind of atom.

     element.       together. Can be only         (H2O, CO2)

        (Cu)            one kind of atoms.

                                 (H2, O2) 

               We also did a paper clip lab. In the lab we basically attached different paperclips together to make molecules. This is a picture of my groups molecules.

 the next scribe is Nazia L.

Achtung Baby

Today was all about safety. Our discussion centered around the Flinn Scientific Safety Contract. Also we watched clips from the ACS safety video. The first part of the discussion talked about appropriate laboratory attire and behavior. The movie clips were hilarious but informative as Mr. Lieberman was able to link them to our classroom. 

The shorter clip had to do with good lab techniques. There are several points that I think are worth highlighting.

1. The video made a point of telling us that it is always smartest to pour liquids from large stock bottles into smaller containers that are easier to manage in the lab.

Ahh...the memories

2. The point of mixing acids is an important one but not done very often in our class. Acids should always be poured into water, not the other way around. "Do what you outta pour the acid into the watta" I know lame but I learned that in high school myself.

3. The video also commented on how we always pour out of stock bottles but never back in. If you have too much of a chemical dispose of it properly but do not put it back into the stock bottle.

4. Remember never mouth pipet!!


The next scribe will be Charles W.