Author: Maddie Van Beek


I’m guessing that at this point, all of you have heard of the dreaded ebola virus. Just in the past few months, US citizens have been more concerned than ever about this horrific disease. In this blog, you will learn a little bit about the background of the ebola virus, as well as how diseases spread. 

Ebola’s History and Mortality Rate

• First identified in 1976 in Congo near Ebola river. 
• Then: 90% mortality 
• Now: 50% mortality 

How did ebola evolve to affect humans?

2014 Ebola Outbreak: Largest in HISTORY

• Ebola is now spreading in West Africa and concentrated in Guinea, Sierra Leone, and Liberia. 
• The number of cases that have occurred during this outbreak have been more than the combined number of cases occurring previous to 2014 combined. 

# of ebola cases 1976-2013 < # of ebola cases in 2014

How does ebola spread? 

As you saw in the video, ebola spreads first from animal to human and then from human to human. Fruit bats, monkeys, gorillas and other primates become infected with ebola and become carriers. People may become infected with ebola by eating uncooked infected meat or coming in contact with infected animals. Once people are infected, they can infect other people by coming in contact with each other’s bodily fluids. 

How is ebola contracted?

Ebola in the US

Although ebola has stayed out of the US in the past, it has recently made its way in, starting with a Texas man who was diagnosed on September 30th, 2014 and passed away on October 8th. The man had traveled from Liberia to Texas, so he was infected in Liberia before coming to the US. Since then, three others have been reported to have ebola. Two of these people who have contracted ebola have been health care workers from the Dallas, Texas, hospital where the first ebola patient was treated, and the third was a New York City doctor who had traveled to Guinea. Both Dallas patients have recovered and the New York City patient is currently being treated. 

Why would health care providers be the ones to get ebola? Shouldn’t they knew the best way to stay healthy?

Health care providers are at a higher risk, since they are treating those who have ebola. Although ebola can only be spread through bodily fluids, treating someone who is vomiting could lead to infiltration of the disease through touching the infected person’s bodily fluids and then touching broken skin or mucus membranes such as the eyes. Health care providers treating patients with ebola have a much higher risk than the average US citizen, since they are in direct contact with the disease. 

Do we need to worry about ebola spreading in the US?

No! The reason ebola spreads so quickly and causes so many deaths in other countries is because they do not have adequate healthcare available to them. In the US, health care providers are not concerned about ebola spreading; as stated, ebola is difficult to contract in its present form and is easily stoppable when the right procedures are followed. 

In order to help control the spread of diseases, teams of healthcare professionals work together to quarantine infected people, immunize people at risk, educate the public about prevention strategies, and treat infected people swiftly and aggressively. 

Currently, there is no safe ebola vaccine. 

Do I need to worry about getting ebola?

Although ebola is very dangerous, you most likely have no need to worry. It’s very difficult to actually get ebola, since you have to come in contact with an infected person’s bodily fluids and then get those bodily fluids in a mucus membrane such as your mouth, eyes, nose, etc. Ebola does NOT spread like a cold--you can’t get ebola from a sneeze or a cough--it’s not an airborne disease. Just like any other virus or disease, you can avoid ebola and help keep it from spreading by washing your hands, not sharing drinks, chapstick, etc., staying home if you are sick, and going to the doctor if you have symptoms. 

And remember, only ebola victims with symptoms are infectious--the disease does not spread until the infected person is already showing symptoms. 

The incubation period for ebola is 2-21 days. This means it may take 2-21 days to show symptoms of ebola. Therefore, if you come in contact with the disease, you should be on watch for about three weeks.

Quick look at ebola vs. the flu:

How do diseases spread, anyway? 
Simulation of how diseases spread: 

This activity is NOT an accurate simulation of ebola--yes, ebola spreads in a similar manner, but with adequate health care and preventative strategies, ebola can be kept from spreading in a manner similar to the simulation. This simulation is just to help you understand how unchecked infectious diseases may spread from person to person. 

YOU WILL NEED: 

Lemon juice

Clear cups

Water

Paper

Writing utensils

A light source

Red and blue food coloring

Water droppers

An iron, and a heat-proof surface to use it on

YOU WILL DO: 

1. Get a group of twenty or so students together.
2. Fill nineteen cups with water and one cup with lemon juice.
3. Hand out the cups, paper, and water droppers to each participant, and don’t announce who has the lemon juice.
4. Explain that there will be six one-minute rounds in this simulation. 
5. You may be wondering what lemon juice could have to do with infectious diseases. Lemon juice can actually be used as “invisible ink,” so the lemon juice represents the invisible infectious disease. One person has lemon juice in their cup, while others only have water. All participants should have a piece of paper with them for round one. 
6. Round 1: Give participants 60 seconds to move around the room; whenever they come in contact with each other, they should take a drop of water from the other’s cup and dot it on their piece of paper. This represents coming in contact with others’ body fluids. 
7. After the 60 seconds is up, use the iron on its hottest setting, and iron everyone’s papers. The heat from the iron will cause the lemon juice to turn brown. Those that came in contact with the lemon juice will have a brownish spot on their paper, while others will just have water spots. Those with the brown spot represent people who have been infected with the disease. Record the number of people who were infected.

Ok, so is this demonstration completely accurate? No! There was only one person spreading the disease. Let’s try something new!


8. Once again, all participants get a cup of water. This time, give one person a red dye dropper. Just like the lemon juice, the red dye represents the disease. Participants get 60 seconds to rotate around the room. The person with the red dye will put a drop of red dye in the cup of each student he or she comes in contact with. Those who receive a red drop will then also become disease carriers (equipped with red dye).  They will continue to spread the disease by putting a drop of red dye into the cup of each person they encounter. 


9. After 60 seconds, analyze how many people have pinkish-colored water--that’s how many now have the virus! 

10. Create two graphs for round 1 and round 2 to demonstrate how many people became “infected” in each round. The Y-axis should be number of people, and X-axis should be time. How do they look different? Which round had more infected people? Which round more accurately demonstrates how quickly a virus can spread? 

You should end up with something like this: 

11. This time, you are going to inoculate 20% of your group. Inoculate means to treat with a vaccine to provide immunity against a disease. Start by putting a few drops of blue food coloring into 20% of the cups. If you have twenty people, four people will get cups with blue water. Repeat step 8. 

12. You could now have some people with red water (people infected with the disease), blue water (inoculated people who did not come in contact with the disease) or purple water (inoculated people who came in contact with the disease). Because inoculated people were protected from the virus, they do not count towards the infected number of people. Before moving on to round 4, record the number of infected students. 

13. Round 4: This time, start by inoculating 40% of the class. If you have twenty people, eight should now start with blue water. Repeat step 8. Record the number of infected students. 

14. Round 5: Start by inoculating 60% of the class. Repeat step 8. Record the number of infected students. 


15. Round 6: Start by inoculating 80% of the class. Repeat step 8. Record the number of infected students. 


16. Make a bar graph for rounds 2-6 and see how inoculation affects the spread of the disease. 

You should end up with something like this:

17. Reflect on this activity. What was not realistic about this simulation? What preventative measures could people take in real life to avoid infection? 

References

• http://www.who.int/mediacentre/factsheets/fs103/en/
• http://www.cdc.gov/vhf/ebola/outbreaks/2014-west-africa/qa.html
• http://www.pbs.org/wgbh/nova/education/activities/3318_02_nsn.html
• http://www.seplessons.org/node/226
• http://youtu.be/qkzIGp1uYoc
• http://www.cdc.gov/vhf/ebola/outbreaks/2014-west-africa/index.html

Have you ever bumped your head or twisted your ankle, and had a nurse put a cold pack on your injury?  You may have noticed he or she did not take the pack out of the freezer—the pack had no ice in it...yet it was still cold!  Or, have you ever been outside on a cold day and used gel hot packs to keep your hands warm?  You may remember breaking a small disk inside the gel, and feeling it get hot to the touch.  Both the cold packs and the hot packs use chemistry to change their temperature! 

When chemical reactions or processes occur, there is always an exchange of energy.  Some of these reactions or processes give off energy as heat; these are called exothermic (‘exo’ meaning outside, ‘thermic’ meaning heat).  Other reactions and processes absorb energy, making the surroundings cooler; these are called endothermic (‘endo’ meaning inside). 

But why are some reactions exothermic while others are endothermic?  Can we predict if a reaction will give off or absorb heat?  As it turns out, we can! 

Chemical Reactions
First, we need to briefly discuss chemical reactions.  A chemical reaction is when one or more chemical compounds are changed into one or more different compounds.  In any chemical reaction, some bonds need to be broken, and others need to be formed—this is how the reaction produces new compounds.  If we know how much energy is required to break the bonds in the reactants (the compounds present before the reaction takes place), and we know how much energy is released on formation of the bonds in the products (the compounds present after the reaction takes place), we can compare them to see how much energy will be produced or consumed by the reaction.  Fortunately for us, there are tables we can use to figure out the energy of the reactants and products. These are called bond energy tables, similar to the one below (1). 

If the formation of the products releases more energy than it took to break the bonds in the reactants, the reaction must give off some of this energy as heat, and so is exothermic.  However, if the formation of the products releases less energy than it took to break the bonds in the reactants, the reaction must take in heat energy from the surroundings, making the reaction endothermic. 

Chemical Processes
The same is true for chemical processes.  A chemical process is what happens when there is a change in the state of one or more chemical compounds (like changing from a liquid to a gas, or dissolving in water), but there is no formation of a new compound.  If we know how much energy the compounds have before they undergo the process (such as melting, or dissolving in water), and how much energy they have after this process, we can discover if the process is endothermic or exothermic.  For example, if we have an ice cube sitting at room temperature, we know the ice cube will begin to melt.  The warmth of the room is melting the ice because the water molecules are absorbing the thermal energy from the air in the room, and this energy is making the molecules move faster and farther away from each other, bringing them from a solid state (ice) to a liquid state (water).  Because this process absorbs energy, it is endothermic.

However, if we put the ice cube back in the freezer, the liquid water will begin to turn back into solid ice.  In this freezing process, the water molecules are giving up thermal energy to their surroundings in the freezer, and are thus losing energy to change states.  This is therefore an exothermic process. 

One type of chemical process that can be either exothermic or endothermic is dissolving of salts in water.  A salt is a compound made up of positively charged ions and negatively charged ions which are held together in a solid state because the positive and negative charges attract one another.  The salt we put on our food is referred to as “table salt”, and is a salt compound made up of sodium ions (Na+) and chloride ions (Cl-). 

If we put salt in water and it fully dissolves (that is, the ions all become evenly dispersed within the water), two exchanges of energy need to happen:

1.       Energy is added to the solution to pull the ions away from each other:  in order to pull the positively and negatively charged ions apart, energy must be added.  This energy needed to pull the ions apart is called the Lattice Energy.

2.       Energy is released into solution when the water molecules surround the ions: as the water molecules are attracted to and surround the ions, energy is released into the solution. This energy released as water molecules surround the ions is called the Hydration Energy.

Whether the dissolving of a salt is exothermic or endothermic depends on which is greater, the Lattice Energy, or the Hydration Energy.  These are usually expressed in units describing the amount of energy released per set amount of salt, such as kilocalories per mole (kcal/mol) or kilojoules per mole (kJ/mol).  We can usually look up the values of the Lattice and Hydration Energy values for a particular salt in tables, such as the one below (2).

For example, if we dissolve table salt in water the Lattice Energy is 779 kJ/mol, and the Hydration Energy is 774 kJ/mol (1).  If we subtract the Hydration Energy from the Lattice Energy, we get a change of +5 kJ/mol:

779 kJ/mol – 774 kJ/mol = +5 kJ/mol

It takes just slightly more energy to separate the ions from one another than is released from the water molecules surrounding the ions.  This means just slightly more energy must be put into the solution than is released back into the solution; therefore dissolving table salt in water is endothermic. 

However, if we dissolve sodium hydroxide (NaOH) in water, it separates into Na+ and OH- ions.  The Lattice Energy for this process is 737 kJ/mol, and the Hydration Energy is 779 kJ/mol.  Subtracting as before, we get a change of -42 kJ/mol.

737 kJ/mol – 779 kJ/mol = -42 kJ/mol

More energy is released into the solution than is required to pull apart the ions; therefore dissolving sodium hydroxide in water is exothermic.  If you dissolve sodium hydroxide in a small amount of water, be careful—the container may get hot enough to burn your hand!

TRY THIS!!

Here’s what you’ll need:

1.       Two small jars or drinking glasses

2.       Two teaspoons

3.       Two cups of distilled water

4.       One half-cup of magnesium sulfate (MgSO4).  You can purchase this online (click here for options).

5.       One half-cup of ammonium chloride (NH4Cl).  You can purchase this online (click here for options).

6.       One thermometer that will measure temperatures from 70-150°F

7.       Safety goggles, one pair for each person participating

8.       Latex or nitrile gloves (you can get these in grocery or hardware stores)

Here’s what you need to do:

NOTE:  Be very careful with the magnesium sulfate and ammonium chloride—they can cause irritation to the skin, lungs and eyes.  Do not breathe them in or get them in your eyes!  You should do this procedure in a well ventilated area, and wear the goggles and gloves to make sure your eyes and skin are protected.

1.       Put on your goggles and gloves!

2.       Pour one cup of distilled water into each of the small jars.

3.       Measure and record the temperature of the water in each jar.

4.       Pour one half cup of the magnesium sulfate into one of the jars.  Stir carefully with a spoon for 20 seconds (don’t worry if not all the magnesium sulfate dissolves).  Measure and record the temperature of the solution.

5.       Pour one half cup of the ammonium chloride into one of the jars.  Stir carefully with a spoon for 20 seconds (don’t worry if not all the magnesium sulfate dissolves).  Measure and record the temperature of the solution.

Did the temperature of the water change each time?  How much did it change?  Did it get hotter or colder?  Are these processes endothermic or exothermic?  Did you observe anything else?  BE SURE TO WRITE EVERYTHING DOWN IN YOUR JOURNAL!


References:

(1)    “Bond Enthalpy/Bond Energy”.  Mr. Kent’s Chemistry Page.  www.kentchemistry.com Accessed 8/28/14.

(2)    “Chapter 13: Solutions”. intro.chem.okstate.edu. Accessed 8/29/14.

This week’s blog is for high schoolers (or anyone else taking a chemistry class)!  If you are in a chemistry class, or have ever taken a chemistry class, you know it’s important to understand how to balance a chemical equation.  A chemical equation is how we can describe the reaction between two atoms or molecules in a concise way (for more information on chemical reactions, click here).  On the left side of a chemical equation are the reactants, or the substances we start with before the reaction.  On the right side of the equation are the products, the substances that are created in the reaction.  For instance, the reaction between hydrogen and oxygen to create water would be written like this:

We would read this equation as “hydrogen reacts with oxygen to produce water”.  You will also notice in this equation that there is a number two in front of the hydrogen, and a number two in front of the water (H2O).  These numbers are called coefficients, and they are there to show us that for this reaction to take place, two molecules of H2 must react with one molecule of O2 to form two molecules of water. 

You may ask, “Why should we need these coefficients?  Why not just write it out as simply as possible?”   Well, if we write out what really happens in the reaction, our equation would look like this:

Yes, this is very simple, but there is a problem with it.  Hydrogen and oxygen (as well as nitrogen and halogens like chlorine and fluorine) don’t appear as single atoms in nature, they appear as molecules with two atoms each. 

In order to understand what is really happening during the reaction, we must write our reactants as they really appear.  This means writing their formulas as H2 and O2 (because one molecule has two atoms of hydrogen or two atoms of oxygen).  Now if we try to write our chemical formula using these correct molecular formulas, we end up with this:

But now we have another problem...now the equation does not balance. 

What we mean by this is that the number and type of atoms from the reactants on the left side of the equation do not match the products on the right side.  We know that in the real world this cannot be the case, because the law of conservation of mass states that atoms are neither created nor destroyed in any chemical reaction. 

Take a look at our last equation again.  On the left there are two hydrogen atoms and on the right there are two oxygen atoms.  On the right there are two hydrogen atoms (this is good), but only one oxygen atom.  This implies that one of the oxygen atoms just disappeared, and we know this cannot be!  This means the equation is unbalanced.  To fix this, we need to add our coefficients.  Let’s start out by bringing back the missing oxygen atom.  We do this by putting the coefficient 2 in front of water.  This means now there are two molecules of water, each of which has one oxygen atom, for a total of two oxygen atoms.

But now on the right side there are four hydrogen atoms:  each molecule of water has two hydrogen atoms, and there are two molecules, for a total of four hydrogen atoms.  We can fix this by putting the coefficient 2 in front of the hydrogen on the left side, giving us a total of four hydrogen atoms on the left side also.

Now our equation is balanced! 

Let’s try another synthesis reaction—the reaction between nitrogen and hydrogen to form ammonia:

Let’s start by balancing the nitrogen.  There are two nitrogen atoms on the left, and one on the right.  We can make these balance by adding the coefficient 2 in front of the ammonia on the right side:

Now the hydrogen must be balanced; there are two hydrogen atoms on the left, and six on the right.  We can make this balance by adding the coefficient 3 in front of the hydrogen on the left side:

This equation is now balanced!

Now let’s try another, more challenging reaction, such as the displacement reaction between aluminum and hydrochloric acid (remember, a displacement reaction happens when atoms of one element displace the atoms of another element in a molecule).  In this reaction, aluminum displaces hydrogen as the bonding partner with chloride:

Clearly this equation is not balanced.  There is one aluminum atom on each side, so this is OK so far.  There is only one hydrogen atom on the left but there are two on the right, and there is only one chloride atom on the left and there are three on the right.  We need to find a way to balance the hydrogen and chloride atoms. 

First, let’s look at the chloride atoms, since this is the largest imbalance between the two sides.  To fix this imbalance, we would need to put a coefficient 3 in front of the hydrochloric acid:

Now, look at the hydrogen atoms.  There are now three on the left and two on the right.  To make this balance we need to find the least common multiple of two and three, which is 6.  This means we need 6 hydrogen atoms on either side of the equation.  This is how our coefficients will look:

Our aluminum is still OK, but now we need to look at the chloride again.  We have six atoms of chloride on the left side, and three on the right.  We can fix this by adding the coefficient 2 in front of the aluminum chloride molecule:

Now our hydrogen atoms balance, and our chloride atoms balance, but our aluminum atoms don’t!  Finally, these also need to balance, so we need two on the left side; we simply add the coefficient 2 in front of the aluminum atoms on the left:

Now all atoms in the equation balance.  This equation required a little more jostling back-and-forth, but don’t let that worry you!  Just keep going back and forth until all the atoms balance, starting with the atoms that are the most imbalanced, and working toward the ones that are the least imbalanced.  This is a little like hitting a baseball, or riding a bike—it takes a little practice to get really good at it!

Let’s try one more, the combustion of propane in oxygen from the air:

Because the oxygen appears in both of the products of the reaction, I’m going to leave oxygen for last.  The greatest imbalance is for hydrogen, with eight atoms on the left, and two on the right.  To make the hydrogen balance, we need to insert the coefficient 4 in front of the water:

Next let’s look at the carbon atoms.  There are three on the left and one on the right, so we need to add the coefficient three in front of the carbon dioxide:

The hydrogen and carbon atoms now balance, what about oxygen?  There are ten oxygen atoms on the right side, so we must add the coefficient 5 in front of the oxygen.

Now all atoms balance on both sides of the equation.

NOTE:  The most important step of balancing a chemical equation is simply making sure that your reactants and products are written correctly.  If they are not, the equation will never balance and you will spend many fruitless hours struggling.  If you are having a lot of trouble getting a reaction to balance, this is usually a good place to start looking for answers! 

TRY THESE!!

Fill in the blanks with the proper coefficients. 

1)      _Al + _O2 = _Al2O3

2)      _Na + _H2O = _NaOH + _H2

3)      _C2H4 + _O2 = _CO2 +_H2

4)      _Si2H6 + _O2 = _SiO2 + _H2O

5)      _CH3OH + _O2  = _CO2 + _H2O

ONLY WHEN YOU ARE DONE....go ahead and scroll down!


 















Answers:

1)      4, 3, 2

2)      2, 2, 2, 1

3)      1, 2, 2, 2

4)      2, 7, 4, 6

5)      2, 3, 2, 4