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Activity (Hands-On)Grades 10 - 12

Mixture Dualism of Blood

An oval diagram in the shape of a blood drop illustrates that blood is composed of many substances; a longitudinal cross section of a blood vessel inside the oval signifies that blood is especially suitable to flow through blood vessels. The blood vessel cross-section exhibits a plug-in formation by the platelets to repair the vascular injury. The diagram also depicts the development stages of blood research and how a deep knowledge about blood phenomena evolved.Blood is composed of many substances.

Students learn about the separation techniques of sedimentation and centrifugation and investigate whether blood is a homogeneous or a heterogeneous mixture. Working in groups as if they are biomedical researchers, they employ the scientific method and make observations about the known characteristics of urine, milk and blood. They probe further by analyzing research on the properties and fractionation modes of blood. As students learn about certain strange characteristics with the fractionation behavior of blood, they formulate hypotheses on the unique nature of blood. Using provided materials —olive oil, tomato juice and petroleum jelly—they design an experiment and construct a blood model. They test their hypotheses by conducting experiments on the blood model, and then propose theories for the nature of blood as a mixture—arriving at the theory of mixture dualism in blood—that blood is a complex mixture system. An activity-guiding handout and PowerPoint® presentation are provided for this student-directed, project-based activity.

This activity establishes for students a connection to real-world applications of separation technology. All sorts of mixture separation processes form the backbone of pervasive everyday industries such as food processing, water treatment, dairy processing and medical blood handling, in which engineers are intricately involved. Learning about two separation techniques—sedimentation and centrifugation—gives students a foundation from which to understand the value of the separation of mixtures concept. In fact, some type of industrial mixture separation processing is key to the chemical, petroleum refining, aluminum, steel, metal casting, glass, and paper and pulp industries. Two examples: The simple lab technique of centrifugation has great commercial and societal value when applied at the industrial-level for materials production. The simple phenomenon of sedimentation of particles from fluid suspension is the basis for the common ESR blood test used to measure body inflammation. Understanding the complex structure and composition of bio-macromolecular mixture systems such as blood is important for biomolecular engineers as they create solutions to life science and health problems.

After this activity, students should be able to:

  • Describe blood as a complex mixture system composed of several mixture subsystems.
  • Explain how blood can separate in different ways under different conditions both inside and outside the body.
  • Analyze why sedimentation and centrifugation are widely used in the separation of blood into its constituents.
  • Show that the ESR clinical test is based on the sedimentation technique for blood separation.
  • Show that most clinical blood analysis tests (other than ESR test) and the blood product industry use the centrifugation technique to separate blood into different components.
  • Formulate a hypothesis on the behavior of blood as a mixture.
  • Construct a blood model from everyday materials by applying the concepts of density, miscibility, solubility, etc.
  • Experimentally demonstrate the sedimentation process in blood, the centrifugation of blood using a blood model, and the relationship between sedimentation and centrifugation.
  • Theorize that blood exhibits mixture dualism.

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