1. After seeing the spectra of various elements in this lab, why do you think an element’s spectrum is often called its “fingerprint?” Explain using the terms ground state, excited state, and electron configuration.
2. Explain how a spectra is formed. Make sure to include the process and the steps that occur. This is important that you can describe what happens during the changes between ground and excited state, and how energy is released and absorbed.
ENRICHMENT:
1. Research the discovery of the element Helium, and why it is given the name it has.
2. Find out how astronomers use what is called a “red shift” or a “blue shift” to know whether a galaxy is moving towards or away from our galaxy. To do this:
a) Explain what blue shifts and red shifts are, and what they have to do with an element’s spectrum.
b) Explain how the ratio of blue shift to red shift galaxies is used as evidence that the universe is expanding.
c) Find out what Sir Edwin Hubble had to do with all this.
This experiment approached electrolytes and then acids and bases from a variety of angles. At the end of the lab and this blog post you should understand:
How to compare electrolytes to non-electrolyes and how to classify electrolytes as acids bases and salts
The basic properties of acids and bases and how they have impact on indicators
What happens in a neutralization reaction and how the difference in concentration has an influence on that reaction
For the first section you need to do the following in a well written paragraph.
Explain the type of bonding that takes place in electrolytes
Explain why electrolytes conduct electricity when they are dissolved in water
Explain why non-electrolytes do not conduct electricity when they are dissolved in water
Find why electrolytes are important to our nervous system
For part II you need to do the following:
Explain in your own words how an indicator works, what happens to them under different conditions, and a limitation of an indicator [hint: bromothymol blue was useful to a certain point].
Mention what the tastes for acids and bases were. From you experience with foods come up with at least on food item that likely contains acidic or basic compounds. If you are unsure look it up.
Find a chemical property for each acids and bases. Hint: You did an mini experiment with magnesium metal. Once again, if need be look another one up.
ENRICHMENT: Look up how indicators really work. This is a little complex and will require you to do some reading, but once you know I think it is pretty cool.
For the final part, you need to do the following:
Explain how a neutralization reaction forms its products. Use an example from the lab if it helps you explain or show. You can use a chemical equation if you need to, but make sure you provide supporting information.
Explain how your thought process that you used to determine which solution was which. Include any information about what you were thinking when you were doing your neutralization. Explain why just using indicator was insufficient to determine which acid was which.
This lab was a lengthy one, so I am looking to make sure that you understand what you did. if you have any questions you can email me, or text 210-CHEM number to get help and pointed in the right direction!
In our miniature sized lab we looked at many different scenarios where a double replacement reaction either resulted in no apparent change, or the formation of a precipitate.
First, take a look at your predictions. Where they all accurate? If not explain which ones did not match up. See if you can figure out what happened. There was one trial that had results that did not match up with the expected prediction. Where you able to find it, which one was it?
Precipitation reactions are very important in water treatment and purification. Find a contaminant that is removed from waste water before it is processed back into nature using a precipitation reaction (hint do a google search). See if this reaction is consistent with the information on Table F (it depends on the ion that is used). Sulfate is an ion that is often used to form precipitates, using Table F why is this a good choice.
Ok so the last experiment that we did really focused in on the reasons that a reaction will proceed at a certain rate. The way that you will need to think about this process has to do with particle collisions and how they influence how fast the reaction will happen. For a reaction to happen we need what is called an effective collision. This means that the particles have collided in such a way that there will be a chemical reaction. The changes we made in the lab, influence the number of effective collisions that were occuring.
The first thing that we did in the lab was try to make a plan so that you could determine how the lab would be done so that you could tell how changing each variable would influence what happened. Describe quickly what you did in the experiment. Include in this description why it was important that you controlled the variables in a certain manner. In the lab pre-assessment that you did we chose that student B was the one that had the best procedure to determine how a variable affected the rate. Why was his method the best? What would happen if you varied multiple variables at the the same time?
By changing the concentration of the vinegar, the temperature of the vinegar, and the amount that the tablet was crushed the rate of reaction was changed. Describe, using particle collisions why each variable changed the rate. Also describe if the results in your experiment were consistent with what you expected to happen. If they aren't, describe something that could have gone wrong in the process.
Enrichment: Do some online research and find an example of a real-life catalyst. Find out what changes in the reaction and how that has a significant influence on the rate of reaction. If you need help getting started catalysts are often used in industrial processes in order to make reactions more efficient. Also, you could look at enzymes and see specifically how they change a biological process.
Now that you have had the chance to digest the heating and cooling curve process a little bit, I am going to ask you guys to think about what happened in the process.
Paragraph #1: Write a clear procedure for what you did in this experiment. This may be in bullet and complete sentence form, or paragraph form. The blogs have been getting better, but the complete sentence issue is a must.
Paragraph #2: Take a look at the graph that you made as a result of the data that you collected. Identify the melting point of lauric acid from your graph. Identify the freezing point from the second graph that you made [many of you put the on the same axis, which is fine]. Are these two values the same (and should they be the same)? Explain how you determined the freezing and melting points from your data.
Paragraph #3: As you heat a substance to its melting point and through the phase change there are changes that occur in both kinetic and potential energy. Explain what kinetic energy is and when it is increasing during your heating curve and decreasing in your cooling curve. Explain what potential energy is, and also explain when it is increasing and decreasing in your curves.
Enrichment:
Lauric acid of course has an actual melting point. Find the actual melting point and compare it to your data. Calculate the percent error and predict a reason why you were high or low (the thermometers are accurate, so don't blame them.)
Find out more about lauric acid. Maybe what it is used for, or could potentially be used for, find its chemical formula, structure, anything relevant about the chemical. Reference the source that you used to find the information.
I am looking for you understanding of how and why the particles in the gases cause the change that you are predicting.
You will not receive full credit if you do not explain with complete sentences.
1. A decrease in pressure causes the volume of a balloon to _______________________.
(increase, decrease or stay the same?)
2. Adding more gas to a bottle ____________________ the pressure in that bottle.
(increases or decreases?)
3. As the volume of a cylinder is increased the pressure will __________________________.
(increase, decrease or stay the same?)
4. Increasing the pressure in a tire by adding more gas will cause the volume to _______________ .
(increase, decrease or stay the same?)
5. As the temperature of a closed container of water is increased the amount of water vapor above the water causes a(n) _________________________ in vapor pressure.
(increase, decrease or no change?)
6. As the air pressure above a liquid is increased by adding more air, the boiling point of the liquid will _____________________. (increase, decrease, or remain the same?)
7. If a balloon filled with air is taken under water to a depth of 10 feet, it’s volume will ______________________ . (increase, decrease, or remain the same?)
8. The temperature of a beaker of boiling water will __________________ as more heat is added. (increase, decrease, or remain the same?)
9. Hot air rises because it is _____________ dense the cold air around it.
(less or more?)
10. When heated, the volume occupied by air in a balloon will ___________________________ .
(increase, decrease or stay the same?)
ENRICHMENT:
Try to explain what happened to the tanker car shown in the pix, in terms of gas particle behavior. The situation happened when some workers cleaned the tanker out with a hot water flush and then sealed the tanker car lid after doing their work in the middle of the day. That night, the air temperature dropped down to the 350F range. The car did this sometime during the night.
