After this activity, students should be able to:

• Describe the purpose of a fever in the body's immune system.
• Create a model of a thermometer and describe its function.
• Give examples of engineering that have helped with the immune system.
• Convert degrees of temperature from Celsius to Fahrenheit.

Have you ever wondered why your parents take your temperature to see if you are sick? They are checking to see if your body is hotter than it should be (98.6° F is considered normal). When your body temperature rises, it is called a fever. Fevers are thought to be one way that the immune system defends itself against germs and infection. By raising your body's temperature, certain bacteria and viruses that are sensitive to temperature changes are destroyed (killed by the higher than normal temperature). However, if a fever is too high, it can cause physical damage or even death, so oftentimes it is necessary to reduce a fever by using aspirin, ibuprofen or some other method.

To check if your body has a fever, your parents or the doctor uses a thermometer. So how does a thermometer know how hot your body really is (i.e., your temperature)? Bulb thermometers contain a type of fluid that changes volume relative to its temperature: heat will make the fluid expand (take up more space), while the cold will make it shrink (take up less space). Mercury is the most common fluid used due to its low freezing point, and high boiling point. In order to see the liquid shrinking or expanding, the mercury is placed in a narrow tube (contained inside a wider-diameter glass tube) to magnify the changes that occur. The interior mercury tube has a bulb at the end of it that is placed on an object to obtain its temperature (i.e., under your tongue if you are sick and need to know your temperature). The final step is calibrating the thermometer (dividing the tube into degrees, either Fahrenheit or Celsius). Degrees are the units of temperature; like meters, they are units of length. The very first thermometer was calibrated by sticking it in freezing water and marking where the fluid was. Then, the thermometer was placed in boiling water and that temperature was marked. Today engineers have developed machines that calibrate thermometers while they are being made.

Engineers need to know about the immune system and how it works. In fact, engineers have developed many of the instruments that help doctors diagnose and treat diseases. Engineers also help develop the vaccinations, antibiotics and disinfectants to help kill germs before they can invade your body. Other engineers help design systems to keep the air we breathe and the water we drink healthy, and yet others develop the instruments to monitor our health at the hospital or doctor's office. It is important for engineers to design devices that will help our immune system maintain a safe temperature in our body and still kill harmful bacteria and viruses.

Today is your chance to make your very own thermometer and see it in action! We are going to study how a thermometer measures temperature and discuss how this relates to our body's immune system.

Before the Activity

With the Students

Since rubbing alcohol is toxic, warn the students to not drink the liquid.

Pre-Activity Assessment

Activity Embedded Assessment

Post-Activity Assessment

For upper grades: To add more math extensions, have the students convert the temperatures on the worksheet to the Kelvin scale (Celsius temperature + 273.15 = Kelvin temperature).

For lower grades: It may be helpful to only complete the last set of problems on the worksheet: converting temperatures from degrees Celsius to degrees Fahrenheit.