Answer:You will use Beer's law. A = εmCl
Explanation: The basic idea here is to use a graph plotting Absorbance vs. Concentration of known solutions. Once you have that you can compare the absorbance value of an unknown sample to figure out its concentration.
You will be applying Beer's law to calculate the concentration.
The equation for Beer's law is: A = εmCl
(A=absorbance, εm = molar extinction coefficient, C = concentration, l=path length of 1 cm)
You should have a data set which was used to create a standard curve. The graph should plot concentration (independent variable) on the x-axis and absorption (dependent variable) on the y axis.
You'll need to add a line of best fit to the data points and determine the equation for the line. The equation should be in y=mx + b form.
y = absorbance (A)
Note: no unit for absorbance
x = concentration (C)
Note: unit is M or mol/L
m = (εm) = slope or the molar extinction coefficient in beers law which has units of M−1cm−1
So A = εmC +b
If you solve for C you should get
C = (A-b)/εm
So if you substract your y-intercept from the absorbance and divide by the slope, you are finding the concentration of your sample.
Here is video of a lab applying this concept.
This simulation from PhET is a great way to review parts of a wave with students. They can explore the relationships of frequency, wavelength and speed of waves. This simulation can be used in place of the classic slinky lab commonly used to teach these concepts.
This simulation allows you to explore the relationship of carbon dioxide, water vapor and atmospheric temperatures. Discover how feedback loops connect carbon dioxide, water vapor levels and temperature. The simulation also allows you to learn about albedo and changes in glacial and sea ice. Another cool feature is the ability to manipulate the amount of CO2 being emitted by human activities.
NGSS Connections: HS-ESS2-2 and HS-ESS2-4
Simulation courtesy of: Concord Consortium http://concord.org.
Make a soda bottle biosphere using materials you have at home and an inexpensive trip to your local aquarium store.
This is a great project to help kids learn about seed germination, photosynthesis, food webs, the water cycle and much more! The project could be even be modified and turned into a great elementary or middle school science fair project!
TIPS & Extension Ideas
This video discusses how osmosis can change the appearance of red onion cells by adding or removing water from the cells.
I recently discovered this model from the Concord Consortium. I love it!
Students can view the processes of transcription and translation for the molecule in its original sequence. The ability to see these steps illustrated so clearly will definitely be helpful to students who can find this topic to be challenging because of its abstractness.
They are also able to edit the DNA molecule. By selecting the Edit DNA button they can type in changes to the DNA sequence. They can also click directly on a nitrogen base (ATGC) and select the type of mutation they want to create in the molecule. They can choose a substitution, deletion or insertion mutation. They can then transcribe and translate their new DNA strand to analyze changes in the RNA and protein (amino acid) sequence.
Another cool feature is that the model shows protein models that illustrate which amino acids are hydrophobic and which ones are hydrophilic.
This video demonstrates how to calculate the percent water in copper (II) sulfate pentahydrate by analysis of its chemical formula.
This video shows an experiment comparing the activity of three metals; Cu, Zn and Mg. The metals are first tested hydrochloric acid, and then hot water to determine their levels of activity.
DNA is copied during interphase (S phase) before mitosis and just before meiosis.
Explanation:In human, mitosis produces diploid daughter cells which have the same number of chromosomes as the parent cell.
Meiosis produces gametes (sperm or egg) which are haploid, meaning these cells have half the number of chromosomes as body cells such as skin cells.
DNA is copied using a process called semiconservative replication. The video below shows how DNA is copied and then discusses the processes by which RNA and proteins are made.
I have my students use computer models including "Building DNA" by Gizmos and an animated review of DNA replication. Students are asked to evaluate strengths and weaknesses of the models.
Lessons on this topic can connect with NGSS crosscutting concepts such as "Systems and Sytem Models" by using computer models and "Structure and Function" by focusing on how the shape and structure of DNA allows the molecule to store genetic information.
Hope this helps!