# Blood Clotting to the Rescue: How to Stop Too Much Blood from Flowing

 Difficulty Time Required Short (2-5 days) Prerequisites None Material Availability Three different chemicals (sodium citrate, sodium alginate, and calcium chloride) need to be specially ordered. See the Materials and Equipment list for details. Cost Low ($20 -$50) Safety Adult supervision may be needed for using a blender. All chemicals in this science project are safe to use (they are common food additives).

## Abstract

Have you ever had a cut or a bloody nose that seemed like it would bleed forever? Though it might have seemed like a long time, it probably did stop pretty quickly. This is because different factors in a person's blood normally work together to plug the opening caused by the cut in a process called blood clotting or coagulation. However, some people have a genetic disorder called hemophilia that causes them to bleed excessively. If a person has hemophilia, he or she is usually missing some of these clotting factors, so it is much more difficult for an opening caused by a cut to be plugged. In this science project, you will investigate how blood clotting normally works, and how it can be affected by an anticoagulant.

## Objective

Create a blood simulation to investigate how an anticoagulant affects coagulation, and how disrupting coagulation can cause blood disorders, such as hemophilia.

## Credits

Teisha Rowland, PhD, Science Buddies

Thanks to Andrew Bonham, PhD, Metropolitan State University of Denver, for feedback and assistance with testing this science project.

## Share your story with Science Buddies!

Last edit date: 2013-11-16

## Introduction

When most people get a small cut on their skin, it bleeds for a little while and then it stops bleeding. The entire process by which the bleeding stops is called hemostasis. Hemostasis is important because losing too much blood can be dangerous, and the bleeding needs to stop in order for the wound to heal. An essential part of hemostasis is coagulation of the blood. When a liquid, like blood, turns into a solid or semisolid substance, the process is called coagulation. For blood, this process is specifically called blood clotting.

So how does coagulation, or blood clotting, cause bleeding to stop? To answer this question, we have to look at four key players in hemostasis that are normally found in the blood: platelets, clotting factors, fibrin, and some specific cell types. As you might already know, your blood is transported throughout your body in small tubes called blood vessels. When a blood vessel is damaged and broken open, such as by getting a cut, you bleed. As soon as this happens, platelets typically rush to the site of the open wound. Platelets are small fragments of cells that stick to the opening in the blood vessel, and when many platelets stick together in the opening, they can temporarily plug the opening. However, the platelets alone do not form a very stable plug, or clot. To reinforce the clot and to better stop the bleeding, clotting factors from the blood join the platelets in the clot. But the clot needs to be stronger yet. To do this, some clotting factors make fibrin, which is a string-like protein that forms a mesh throughout the clot, holding the other factors in place. Cells flowing in the blood—specifically red and white blood cells—also join the clot. Talk about teamwork! Once the cells around the clot have healed and closed the wound, the clot is naturally dissolved by the body. Watch the video below to see hemostasis and blood coagulation in action.

This video gives an introduction to how blood clotting works to heal a wound.

You can probably imagine just how important coagulation is for keeping our bodies healthy and strong, so it should not be surprising to find that when it does not work correctly, it can cause serious bleeding disorders, also known as blood disorders. One such disorder is hemophilia (or haemophilia), which is specifically a genetic disorder where the body has difficulty clotting blood; thus, individuals with hemophilia can bleed excessively. This bleeding is often internal, such as in joints (which consequently can swell and become painful), and can be caused by a minor injury (like falling or being hit by something). People with hemophilia may also notice excessive bruising on their skin, or blood in their urine. Excessive bleeding can also happen at the site of external injuries (like cuts) or at minor surgery sites. About 1 in 5,000 males have hemophilia (hemophilia, because of how it is inherited, is rare in females), and it is thought that about 75% of people with hemophilia are not properly diagnosed, so they are not receiving the right treatment (Novo Nordisk Haemophilia Foundation, 2011). Hemophilia occurs when a person has a decreased number of clotting factors (or defective clotting factors). There are about a dozen different clotting factors that work together during coagulation, and people with hemophilia usually have one of two specific factors that are decreased in numbers. As a result, the coagulation process does not happen correctly, and cuts can excessively bleed. Treating a person with hemophilia often involves injecting him or her with some of the clotting factors that they are missing.

Now, here is a challenging question. Can you think of a situation where people would want to prevent blood from clotting? There are actually a few situations where this is important. Some people are at risk of having the blood that is flowing through a blood vessel get blocked by a clot, perhaps because they have been bedridden and their muscles are not properly pushing the blood through their body anymore, or because their blood vessels have narrowed due to a buildup of plaque. If a person develops an unwanted blood clot, it can stop blood from flowing to major organs like the heart or the brain, and can cause a heart attack or stroke. These people are prescribed drugs called anticoagulants (a type of blood thinner) to help prevent this from happening. Scientists and medical practitioners also use anticoagulants in blood samples—such as those taken for blood donation—so that the samples do not coagulate. A commonly used anticoagulant is trisodium citrate.

In this human biology and health science project, you will investigate how an anticoagulant affects coagulation and how disrupting the coagulation process can cause blood disorders, such as hemophilia. The anticoagulant you will use is sodium citrate, which functions similarly to trisodium citrate (mentioned above), but is more readily available, and is completely safe to use. So how do trisodium citrate and sodium citrate act as anticoagulants? It actually has to do with calcium. It is a complex process, but basically, during blood clotting, the platelets increase the amount of calcium that is around the wound, which affects how different proteins interact with the clotting factors. In a chemical reaction, trisodium citrate grabs the calcium. It does this by breaking apart into sodium and citrate, and the citrate technically chelates (pronounced CHEE-lates), or binds to, the calcium, thus forming calcium citrate. This means there is no longer an increased amount of calcium present, and the coagulation process stops. Similarly, the sodium citrate you will use in this science project can also chelate, or bind to, calcium.

It is important to note that in this science project, you will not use real blood (due to potential health hazards), but will instead use a few chemicals that can also coagulate like blood. Specifically, you will use solutions of sodium alginate and calcium chloride. A solution is when one substance is completely dissolved in another, such as when sugar is dissolved in hot water. Alginates, like sodium alginate, are made from seaweed and can form gel-like substances under the right conditions. For example, when a drop of sodium alginate solution is put into a calcium chloride solution, the drop actually coagulates and turns into a semisolid ball! Figure 1, below, shows examples of this. Just like blood needs calcium to coagulate, the sodium alginate needs calcium (from the calcium chloride solution) to form the semisolid balls. In this chemical reaction, the chemicals rearrange so that alginate is bound to calcium, forming calcium alginate, which is a gelatinous substance. For the chemistry-savvy student, the chemical reaction is shown in Equation 1, below.

 Figure 1. When a solution of sodium alginate is dropped into a calcium chloride solution, semisolid, transparent balls form (which are made of calcium alginate). The balls shown here were made using green food coloring. Each ball is about the size of a drop of water. This technique is actually commonly used in molecular gastronomy, which is an area of food science that explores the chemical changes that go on during cooking. Using this technique, people can make little spheres of tasty food, such as fruit juice!

Equation 1:
Sodium alginate (NaC6H7O6) can react with calcium chloride (CaCl2) to make calcium alginate (C12H14CaO12), which is a gelatinous substance.

Did you lose track of all the chemicals introduced? Table 1, below, will help summarize the important information presented here.

 What it is in the human body What you will use in thisscience project Substance that requires calcium to coagulate Blood Sodium alginate solution Source of calcium for coagulation Platelets that increase the amount of calcium around the wound Calcium chloride solution End product of the coagulation process Blood clot Semisolid ball of calcium alginate Anticoagulant (that works by chelating the calcium) Trisodium citrate Sodium citrate
Table 1. This table lists the substances and chemicals in the human body, and what the similar components are that you will use in this science project.

Do you think the balls of calcium alginate (representing blood clots) will still be able to form if sodium citrate (representing the anticoagulant) is added, or will it actually prevent coagulation? If coagulation is prevented, what do you think will happen to the sodium alginate solution (representing blood) that is dropped into the calcium chloride solution (representing an increase in calcium from the platelets)? Will the balls still form just like they did without the sodium citrate, or will they be changed somehow? Get ready to answer these questions and investigate how blood clotting works!

## Terms and Concepts

• Hemostasis
• Blood
• Coagulation
• Blood clotting
• Blood vessel
• Platelet
• Clotting factors
• Fibrin
• Red and white blood cells
• Hemophilia, or haemophilia
• Anticoagulant
• Trisodium citrate
• Chelation
• Solution
• Controls

### Questions

• What are the different key players in hemostasis? What do they do?
• Why can a person with hemophilia have excessive bleeding?
• What are anticoagulants? What are they used for?
• How does trisodium citrate prevent coagulation?
• What do you think will happen when sodium alginate solution is dropped into a calcium chloride solution that has sodium citrate in it?

## Bibliography

You can do further research by visiting the following websites, which give information about hemostasis, blood coagulation, and hemophilia:

In this science project a food preparation technique called "spherification" is used. This technique is often used in molecular gastronomy (an area of food science that explores the chemical changes that go on during cooking) and you can find out more about spherification at the following website:

For help creating graphs, try this website:

## Materials and Equipment

• Graph paper (1 or 2 sheets) with lines that are 1 mm or, ideally, 2 mm apart; available from office or school supply stores or you can print free online graph paper with lines that are 2 mm apart.
• Cold tap water
• Graduated cylinder, 100 mL; available from Amazon.com
• Blender (large or small)
• Digital scale with 0.1-g increments. A digital scale that would be suitable (the Fast Weigh MS-500-BLK Digital Pocket Scale) is available from Amazon.com.
• Wax paper (1 sheet)
• The following chemicals, which can be found in some molecular gastronomy kits: sodium alginate (2 g); calcium chloride (4 g); sodium citrate (6 g). A spherification molecular gastronomy kit that would be suitable is available from Amazon.com.
• Food coloring, any color (5 drops)
• Bowls (3); must be able to hold at least 240 mL (1 cup) each
• Sticky notes (3) or scrap paper and tape
• Spoons (at least 7); for measuring out the chemicals, mixing the solutions, and removing the sodium alginate balls
• Plastic wrap
• Timer, stopwatch, or clock that shows seconds
• Syringe without a needle, or a medicine dropper; medicine droppers are available at most grocery or drug stores in the drug/pharmacy section. Note: If you are using the spherification kit from Amazon.com, the kit comes with a syringe that you can use.
• Optional: Camera
• Optional: Adult helper for using the blender
• Lab notebook

Disclaimer: Science Buddies occasionally provides information (such as part numbers, supplier names, and supplier weblinks) to assist our users in locating specialty items for individual projects. The information is provided solely as a convenience to our users. We do our best to make sure that part numbers and descriptions are accurate when first listed. However, since part numbers do change as items are obsoleted or improved, please send us an email if you run across any parts that are no longer available. We also do our best to make sure that any listed supplier provides prompt, courteous service. Science Buddies does participate in affiliate programs with Amazon.com, Carolina Biological, and AquaPhoenix Education. Proceeds from the affiliate programs help support Science Buddies, a 501( c ) 3 public charity. If you have any comments (positive or negative) related to purchases you've made for science fair projects from recommendations on our site, please let us know. Write to us at scibuddy@sciencebuddies.org.

## Experimental Procedure

### Investigating Coagulation

In this part of the science project, you will make semisolid (gelatinous) balls using a solution of sodium alginate (dyed with food coloring) and a calcium chloride solution. This calcium chloride solution (which will have no anticoagulant in it) will be your control solution, meaning the one that should give clear, expected results and serve as a reference. The calcium in the calcium chloride solution should react with the sodium alginate to coagulate and form semisolid balls (made of calcium alginate), similar to the ones shown in Figure 1 in the Introduction. This coagulation process is similar to what happens in blood to form blood clots. To study the effect of anticoagulants on coagulation, you will test the effects of adding different amounts of sodium citrate (an anticoagulant) to the calcium chloride solutions. How do you think this will change your results? You will quantify your results by measuring the dimensions of the balls you make. Note: In this science project, we will refer to the calcium alginate products as "balls," but this does not mean they will necessarily be spherical.

1. As mentioned above, you will be measuring the dimensions of the semisolid balls of sodium alginate to quantify your results. To do this, you should use graph paper with lines that are 1 millimeter (mm) or 2 mm apart. Then, when you later make the balls, you will place them on a sheet of graph paper to determine the balls' diameters. You will measure the balls' heights by using a cut-up piece of graph paper.
1. To measure the balls' heights, cut off the edge of a sheet of graph paper so that the first lines of the grid are right at the edge of the paper. You could use part of the same sheet you are using to measure the balls' diameters, or you could use a new sheet. (You could cut out a strip of graph paper, making it like a ruler, if that is easier to work with.) Then, when you make the balls, you will place the cut-up graph paper behind the balls to determine their heights. For an example of how this should be done, see Figure 5, below.
2. Note: The reason why you are cutting off the edge of the sheet of graph paper (and not using an uncut sheet of graph paper or an actual ruler) to measure the heights of the balls is because most graph paper and rulers have a little bit of space before the first marks. When you are making small measurements, this extra space could cause inaccurate measurements.
2. In your lab notebook, make a data table like Table 2, below. You will be recording your results in this data table.
 Diameter (mm) Height (mm) Observations Ball Longest diameter Shortest diameter Average No sodium citrate 1 2 3 4 5 Average 1% sodium citrate 1 2 3 4 5 Average 1.5% sodium citrate 1 2 3 4 5 Average
Table 2. In your lab notebook, make a data table like this one. In it, you will record your semisolid ball measurement results. If no balls form, the diameter and height should be "0." Note: The "balls" may not be spherical.
1. Now make the sodium alginate solution.
1. In the cup part of a blender, add 120 milliliters (mL) (1/2 cup [C.]) of cold tap water.
2. Weigh out 2 grams (g) of sodium alginate and add that to the water in the cup.
1. To weigh out the sodium alginate and other chemicals used in this science project, cut a small piece of wax paper (around 8 cm–10 cm on each side), place the wax paper on the scale, zero out the scale (so that it reads "0 g"), and then weigh out the chemical on the wax paper. Use a clean spoon to scoop the chemicals out of their containers. Note: You should use wax paper because it is harder for chemicals to stick to than normal paper.
2. Tip: If the scale you are using does not have a feature to zero it out, you will need to first weigh the piece of wax paper so that you can subtract this weight from the total when you weigh the chemicals on it.
3. Add five drops of food coloring to the blender cup.
4. Add another 120 mL (1/2 cup) of cold tap water to the cup.
1. Adding the rest of the water now should help mix the sodium alginate and food coloring a little.
2. Your blender should now look similar to the one in Figure 2, below.

 Figure 2. After adding the water, sodium alginate, and food coloring to the blender, it should look similar to the blender cup shown here. Note: The coloring of your mixture will be different if you did not use green food coloring.

5. You might want to ask an adult to help you use the blender to blend the water, sodium alginate, and food coloring so that the solution is fluid. When you are done blending, the solution should look like the one in Figure 3, below.
1. Secure the blender cup lid tightly before blending so nothing gets spilled.
2. Tip: It may be easiest to make the solution fluid by blending the contents two or three times, for 5–10 seconds each time; if possible, shake the cup in between blendings.

 Figure 3. After blending the water, sodium alginate, and food coloring together, you should have a solution that is homogeneous (all of the solution's parts are now mixed together and the solution looks the same throughout).

2. Next make the calcium chloride solutions. You will make three different calcium chloride solutions with different concentrations of sodium citrate (the anticoagulant).
1. Set out three bowls.
2. Label the three bowls using sticky notes or pieces of paper and tape.
1. One bowl should be labeled No sodium citrate, another should be labeled 1% sodium citrate, and the last should be labeled 1.5% sodium citrate. Note: The solution with no sodium citrate added will be your control because it should give clear, expected results (in other words, semisolid balls should form).
3. Add 240 mL (1 C.) of water to each bowl.
4. Then add 1.3 g of calcium chloride to each bowl.
1. Measure out the calcium chloride as you did in step 3b.
2. Be sure to use a fresh piece of wax paper so no leftover sodium alginate contaminates your solution.
5. To the bowl labeled 1% sodium citrate, add 2.4 g of sodium citrate.
1. This is a 1% solution because 2.4 g divided by 240 mL equals 0.01, which equals 1% (0.01 multiplied by 100).
6. To the bowl labeled 1.5% sodium citrate, add 3.6 g of sodium citrate.
1. Can you figure out why this is a 1.5% solution?
7. Stir each bowl using a different, clean spoon until the calcium chloride and sodium citrate have completely dissolved.
3. Test if you can make sodium alginate balls using your different calcium chloride solutions. You should try to make a total of at least five balls with each particular solution, making and measuring only one ball at a time. Repeating your results ensures that they are robust and reproducible.
1. Place a small piece of plastic wrap on a sheet of graph paper (for measuring the balls' diameters). Make sure the graph paper you prepared in step 1.a. (for measuring the balls' heights) is nearby.
2. Make sure a timer, stopwatch, or clock that shows seconds is ready nearby.
3. Using the syringe that came with the spherification kit, or a medicine dropper, suck up a small amount of the sodium alginate solution.
1. If there is a layer of foam on the top of the solution, dip the syringe below that layer so you only suck up the liquid part.
2. If there is any foam or excess solution on the sides of the syringe, carefully wipe it off on the rim of the sodium alginate container.
4. Practice releasing the sodium alginate solution very slowly back into its container. You want to get used to making one drop at a time.
5. Once you can make one drop at a time, drop a single drop into the bowl containing the solution of calcium chloride without sodium citrate (your control solution).
1. The tip of the syringe should be around 8–13 cm (3–5 inches) above the surface of the solution.
6. Let the drop sit in the solution for 60 seconds (sec); the timing is important.
7. After 60 sec, try to use a clean spoon to scoop the ball out of the solution, taking care to scoop as little of the solution out as possible without damaging the ball.
1. If nothing clearly formed, make a note of this in your lab notebook. Do this by recording the diameter and height as a zero in your data table.
2. Note: When using the solution of calcium chloride without sodium citrate, a semisolid ball should form, so if it did not, you may want to re-check to make sure your solutions were prepared correctly.
8. Measure the diameter of the ball by placing it on the plastic wrap on top of the graph paper and counting how many lines the ball spans. Note your findings in your data table.
1. Move the plastic wrap around a little until the edge of the ball lines up with one of the lines, as shown in Figure 4, below.
2. Based on the number of lines the ball spans, calculate the ball's diameter in millimeters. If your graph paper has lines that are 2 mm apart, this means you will multiply the number of lines the ball spans by two.
1. For example, in Figure 4, the ball spans about 2.5 lines on graph paper that has lines that are 2 mm apart. This means the ball has a diameter of 5 mm (since 2.5 times 2 mm equals 5 mm).
3. If the ball is not a sphere, measure its longest diameter and its shortest diameter and record both diameters in your data table. (Move the ball around by carefully moving the plastic wrap.) If the ball is a sphere, record the same number for both diameters. Record the diameters in millimeters.
4. Tip: If there is liquid around the ball, making it difficult to measure, you can carefully dab the liquid with a small piece of paper towel to remove the liquid. If you damage the ball when doing this, do not record the measurements for this ball and instead create a new ball in this solution (by repeating step 5.c.–5.h., and continuing from there). You may also want to record these observations in your lab notebook.

 Figure 4. To measure the diameter of the ball, carefully move the plastic wrap so that one edge of the ball is lined up on a line, as shown here. Then count how many lines the ball spans. Measuring from the leftmost line, this ball spans about 2.5 lines, and since the lines in this graph paper are 2 mm apart, this ball has a diameter of about 5 mm (2.5 times 2 mm equals 5 mm).

9. Measure the height of the ball by placing the graph paper you prepared in step 1.a. behind the ball, as shown in Figure 5, below.
1. Make your eye level with the ball and graph paper, such as by lowering your eye to the level of the counter or surface that you are using.
2. Record the height of your ball (in millimeters) in the data table in your lab notebook. Be sure to account for whether you are using graph paper with lines every 1 mm or every 2 mm.

 Figure 5. To measure the height of the ball, place the graph paper you prepared in step 1.a. behind the ball. Make your eye level with the ball and the graph paper and read how high the ball reaches on the graph paper. In this image, the ball and graph paper are not completely level (the viewer would need to lower his or her head to be level and make an accurate reading).

10. Repeat steps 5.c.–5.i. four more times so that you have made and measured a total of five balls using the solution of calcium chloride without sodium citrate.
1. Make sure to record your data in the data table in your lab notebook.
11. Repeat steps 5.c.–5.j., but this time use the 1% sodium citrate solution.
1. Try to make and measure at least five balls using this solution. Be sure to let each drop sit in the calcium chloride solution for 60 sec; the timing is important.
2. Make sure to record your data in the data table in your lab notebook.
12. Repeat steps 5.c.–5.j., but this time use the 1.5% sodium citrate solution.
1. Try to make and measure at least five balls using this solution. Be sure to let each drop sit in the calcium chloride solution for 60 sec; the timing is important.
2. Make sure to record your data in the data table in your lab notebook.
4. When you are done testing, make some general observations about the balls. How do they look and feel compared to each other? Record your observations in the data table in your lab notebook.
1. If you have a camera, you may also want to take pictures of your results. You may want to take some from above and some from the side. Later, you could print your pictures and put them on your Project Display Board.

In this part of the science project, you will analyze your data and come up with conclusions related to coagulation and blood clotting.

1. Look at the data table in your lab notebook and calculate the average diameter for all of the balls. Record these numbers in your data table.
1. For example, if the widest diameter of a ball was 6 mm, and the shortest diameter was 5 mm, the average diameter would be 5.5 mm (since 6 mm plus 5 mm equals 11 mm, and 11 mm divided by two [the number of measurements] is 5.5 mm).
2. If the widest and shortest diameters were the same (which would be the case if the ball was a sphere), the average diameter should equal these diameters.
2. Next, calculate the average ball diameter and height for each of the three different solutions. Record these numbers in your data table.
1. For example, if the average diameters of the balls for one solution were 6 mm, 5.5 mm, 6 mm, 6 mm, and 6.5 mm, the average diameter would be 6 mm for that solution (since the sum of these numbers is 30 mm, and divided by five [the number of measurements] is 6 mm).
3. Make two bar graphs of your data: one graph of the average diameter for the balls made using the different solutions and one graph of the average height for the balls made using these solutions.
1. You can make your graphs by hand or use a website like Create a Graph to make the graphs on a computer and print them.
2. For both graphs, put the solution names on the x-axis (the horizontal axis going across). Put either the average diameter or height (in mm) of the balls on the y-axis (the vertical axis going up and down).
1. This means you should have three bars on each graph, one labeled No sodium citrate, one labeled 1% sodium citrate, and one labeled 1.5% sodium citrate.
4. Look at your data table, graphs, and observations and try to draw conclusions from your results.
1. How did the balls change as more and more sodium citrate was added? Do you think your results indicate that the sodium citrate disrupted the coagulation process? Why?
1. Did the balls' diameters and heights change in the same way (in other words, they both increased or decreased as more sodium citrate was added) or did they change in opposite ways (in other words, the width increased while the height decreased)? What does this tell you about how their overall shapes changed?
2. What do your results tell you about how coagulation and anticoagulants work?
3. Based on your results, why do you think coagulation is important in the blood clotting process? How do you think disrupting blood clotting can cause blood disorders?

## Variations

• You could try this science project again, but this time use solutions with slightly more or less sodium citrate, such as 0.5% or 2%. How does changing the amount of sodium citrate affect the formation of the balls? What is the smallest amount of sodium citrate needed to see a change compared to having no sodium citrate in the solution? Alternatively, if you take a calcium alginate ball and put it in a solution with more sodium citrate (than the solution it formed in), what happens to the ball?
• This science project uses calcium chloride as a source of calcium to form the alginate balls (which are made of calcium alginate). Would other sources of calcium work instead of the calcium chloride? For example, you could try dissolving antacid calcium tablets that are used to relieve an upset stomach. Such tablets usually contain calcium carbonate. Does this calcium source work just as well? Is it affected by the sodium citrate anticoagulant?
• You created calcium alginate balls by letting them sit in the calcium chloride solution for 60 sec, but what happens if you let them sit in the solution for more or less time? For example, how does 5 sec compare to 30 minutes (min)? What does this tell you about the coagulation process?
• Some animals, such as leeches, actually secrete anticoagulants. Can you think of a way to use leeches in a science project to investigate coagulation and blood disorders? You can order leeches from Carolina Biological. Be sure to check with your science fair's Scientific Review Committee before starting this science project to make sure your science project complies with all local rules regarding using biological materials. For more information on this, you can visit these Science Buddies resources: Projects Involving Potentially Hazardous Biological Agents and Scientific Review Committee. Also, many science fairs follow ISEF Rules & Guidelines.
• "Spherification"—the molecular gastronomy technique you used in this science project—can be affected by pH, or how acidic or basic the solutions are. Try changing the pH of your sodium alginate solution (by adding acids or bases to make it more acidic or basic) and see how it affects the formation of the balls. You can try this both with and without sodium citrate. For more background information, visit Science Buddies resource Acids, Bases, & the pH Scale. Be sure to always follow the proper safety precautions when using different chemicals. To confirm the pH of your solutions, you can use pH test strips, which are available from Amazon.com.
• Can you think of another way to model blood clotting and blood disorders? For example, maybe you could model a blood vessel by using a plastic tube, and you could model blood clotting by blocking the tube or an opening in the tube with something like modeling clay and/or marbles. Can you make an accurate hands-on model of coagulation? What about a model showing blood disorders? Tip: You may want to do further research on blood vessels, coagulation, and blood disorders to do this variation and to model some of these processes.
• Hemophilia is a genetic blood disorder. What exactly are the genetics behind hemophilia? To answer this, you could use the Science Buddies Project Idea From Genes to Genetic Diseases: What Kinds of Mutations Matter?, which uses bioinformatics databases, and focus on investigating hemophilia. You may even want to think about how genetic disorders can be treated using gene therapy. Here are some helpful articles on gene therapy: Gene Therapy Arrives in Europe and Targeting DNA.
• You could devise a way to investigate blood clotting by using real (but non-human) blood, but you will need to be sure to follow all of your science fair's safety rules and guidelines. Also, most blood you can purchase is already treated with anticoagulants, so you may want to find a safe source that has not been treated yet. For more information, visit the Science Buddies resources on Projects Involving Potentially Hazardous Biological Agents and the Scientific Review Committee. Also, many science fairs follow ISEF Rules & Guidelines.

## Share your story with Science Buddies!

The Ask an Expert Forum is intended to be a place where students can go to find answers to science questions that they have been unable to find using other resources. If you have specific questions about your science fair project or science fair, our team of volunteer scientists can help. Our Experts won't do the work for you, but they will make suggestions, offer guidance, and help you troubleshoot.

## If you like this project, you might enjoy exploring these related careers:

### Hematologist

Hematologists are all about blood. They diagnose people with blood disorders and prescribe or administer appropriate treatments. There are many different types of blood disorders, including bleeding disorders and blood cancers. Hematologists also investigate ways to improve diagnosing and treatment of these disorders. Read more

### Pathologist

Do you enjoy solving mysteries? Getting to the end of a "who did it" mystery novel can be lots of fun! But are there mysteries in real life? You bet there are! A pathologist is a medical detective, and their job is to figure out the root cause of real-life medical puzzles. Pathologists work in a wide range of fields and can help diagnose types of cancer, find out what killed a person, and investigate how disease progresses on a molecular level. If you enjoy employing cool logic to solve mysteries, then you should seriously consider a career as a pathologist. Read more

### Pharmacist

Pharmacists are the medication experts. They advise doctors, nurses, and patients on the correct drug dosage for a patient's weight, age, health, and gender; on interactions between drugs; on side effects; on drug alternatives; on costs; and on ways to give drugs. They also dispense drugs at pharmacies, according to prescriptions, checking for dangerous drug interactions, and educating patients on how to take drugs, what reactions to watch out for, and how long it should take for drugs to work. Read more

### Biochemist

Growing, aging, digesting—all of these are examples of chemical processes performed by living organisms. Biochemists study how these types of chemical actions happen in cells and tissues, and monitor what effects new substances, like food additives and medicines, have on living organisms. Read more