Week 33 – Zombie Parasites

Now that you have learned about the many different ways organisms can live together,  we will focus on the type of symbiotic relationship called parasitism.  We will begin by watching a National Geographic video about zombie parasites.  The presenter, Anand Varma, applies his expertise in photography to the study of parasites.  Mr. Varma travels the world collecting specimen for study, and his ability to apply biological concepts to his work, think creatively, and drive to overcome failure make him and his work truly remarkable.

Next, read the article Meet the Parasites That Control Human Brains.  In your Week 33 Google Doc, create a section titled “Zombie Parasites” and share your thoughts on the following questions:

• Why do zombie parasites persist?
• What niche do they fill within an ecosystem?
• Think about behaviors you see in yourself and those around you.  Ever wonder why people do what they do?
• Does the existence of zombie parasites cause you to think differently about people and their actions?

Return to the Week 33 – Co-Evolution post and continue our work for the week.

Week 33 – Stoichiometry

Welcome to Week 33!  For this week, we will be focusing on stoichiometry: the quantitative relationship between reactants and products in a chemical reaction.  As a question: How do you convert between grams and moles to determine the mass of product in a chemical equation?  Please work through the list of links below.  Each section contains important information and ends with a portion of the weekly assignment.  You can complete it all in one sitting or break it up as needed.  Ready, set, go!

1. Week 33 Attendance Check-In (required)
2. Mole Ratios (Google Form assignment)
3. Going Through the Mole Tunnel (Google Form assignment)
4. Limiting Reactants (Google Form assignment)
5. Percent Yield (Google Form assignment)
6. Summary of Stoichiometry (encouraged)

You did it!  Just to make sure, here’s a checklist of items you must complete this week by Sunday, May 10 at 11:59pm:

• Weekly Attendance Check-In (school district requirement)
• Mole Ratios Google Form (worth 10 assignment points)
• Mole Tunnel Google Form (worth 10 assignment points)
• Limiting Reactants Google Form (worth 10 assignment points)
• Percent Yield Google Form (worth 10 assignment points)

Remember, you can email me any time.  Office hours for Science are Tuesdays from 11am-12pm and Thursdays from 1pm-2pm.  Check your student Gmail for Zoom instructions.

Finally, by popular demand…click here for the Week 33 Bonus Credit Opportunity!

Week 33 – Going Through the Mole Tunnel

Now that we understand the role of coefficients in chemical equations, we can convert between grams and moles to determine the mass of the products that result from a chemical reaction.  Let’s conduct an experiment where we combine copper and silver nitrate.

Here is the following balanced chemical reaction:

Cu(s) + 2AgNO₃(aq) → Cu(NO₃)₂(s) + 2Ag(s)

First off, let’s notice this is a single replacement reaction.

AB + C → A + CB, where Cu = A, NO₃ = B, and Ag = C

• Question: Find the mole ratio of AgNO₃ to Cu(NO₃)₂  Answer: 2:1
• Question: Find the mole ration of AgNO₃ to Ag  Answer: 1:1
• Suppose you have 6.0 mol of Cu.
  • Question: How many moles of AgNO₃ are needed to react completely with 6.0 mol of Cu? Answer: The mole ratio is 2 moles of AgNO₃ to 1 mole of Cu, so to completely react 6.0 mol of Cu, you need twice as many moles of AgNO₃ (12 mol).
  • Question: How many moles of Cu(NO₃)₂ are produced? Answer: The mole ratio of Cu(NO₃)₂ to Cu is 1:1, so if you have 6.0 mol of Cu, you produce 6.0 mol of Cu(NO₃)₂.
• Suppose you want to make 30.0g of Ag.
  • Question: How many moles of Ag is that? Answer: The molar mass of Ag is 107.9 g/mol.  30g x (1mol / 107.9g) = 0.278 mol Ag
  • Question: How many moles of Cu do you need? Answer: The mole ration of Ag to Cu is 2:1, so with 0.278 mol Ag, you would need 0.139 mol of Cu.

Imagine we actually want to do this single replacement experiment where we produce 30.0 g of silver.  You go to the chemical supply shelf and locate the bottle of copper and silver nitrate.  Both are in solid form.  Now what?  The Mole Tunnel!  In the real world, we work in mass quantities like grams.  To move through a chemical reaction from products to reactants (or vice versa), you go from grams to moles to grams.

We know we need 0.139 mol of Cu.  The copper:silver nitrate ratio is 1:2, so we need twice as many moles of silver nitrate, or 0.278 mol AgNO₃.  To actually do this experiment, we need to use counting by weighing, which means converting moles to grams.  To convert moles to grams, we need molar mass (g/mol).  For Cu, the molar mass is 63.55 g/mol.  For AgNO₃, the molar mass is 169.9 g/mol.

• 0.139 mol Cu x 63.55 g/mol = 8.83 g of Cu
• 0.278 mol AgNO₃ x 169.9 g/mol = 47.2 g of AgNO₃

Done!  You successfully navigated the Mole Tunnel!  You started with grams (30 g), converted to moles, compared mole ratios, then converted back to grams.  By combining 8.83 g of Cu with 47.2 g of AgNO₃, you will produce 30 g of Ag.  Math!

Your turn!  Complete the Mole Tunnel Google Form before returning to Week 33 – Stoichiometry to continue working.