The Science of Tea: Reviewing Energy Transfer

By Laura Hospitál on Jan 21, 2016

Students learn about the transfer of energy through conduction, convection, and radiation.  This interactive activity reviews these concepts while students make and drink tea.  It should therefore be completed soon after these terms have been taught. 

Vocabulary:

(These definitions are examples. Have students use the definitions that come from your text if applicable.)

  • Conduction: heat transfer between substances that are in direct contact
  • Convection:  The circular motion that happens when warmer gas or liquid rises while cooler gas or liquid falls.  This occurs because the warmer gas or liquid is less dense and its particles are moving faster.
  • Radiation:  heat transfer in which the item heated and the heat source are not touching, e.g. sun's radiation

References:

Materials

  • Several varieties of tea bags.  If caffeine is not desirable, choose herbal teas.  Possible herbal teas are orange spice, peach, apple, rooibus (an African root), or hibiscus.  
  • A hot plate
  • Clean pot for heating water
  • Hot pads or mitts for removing the glass container

Procedure

  • Begin the activity by introducing several varieties of tea in tea bags to the students.hot plate with electric coil
  • Allow the students to smell the teas and to choose one to try.
  • Pass around the pot  and the hot plate before plugging it in.  Explain to the students that you will be plugging it in and where it will be in the room.  Include a safety precaution for students who have not used a hot plate. Fill the pot with water and turn on the hot  plate but do not place it on the hot plate until after radiation has been discussed (See below.)
  • Ask the students:  "How do you think making tea can be related to the forms of energy transfer that we have been discussing?"   Discuss their answers, but don't discuss the listed parts of the activity yet.
  • Review the three forms of energy transfer in the following manner:

  1.  Radiation:

  • When you turn on the hot plate, with much supervision, guide carefully each student's hand (one at a time) over the hot plate at a distance that is safe, but that allows the student to feel the heat of the hot plate. 
  • Ask the student which form of energy transfer this represents. 
  • Allow the student to think and remind him of the three forms of energy transfer.  
  • Discuss.  There is not contact between the hot plate and your hand.  When energy transfer occurs but the heat source and the object heated are NOT touching, the form of energy transfer is radiation.

Safety note:  Radiation should be discussed with one student at a time while the other students are at their desks.

  2.  Conduction

  • This example may be discussed as a class.  
  • Ask the students why the pot is heating up. What form of energy transfer is occurring?  Allow students to each think about the answer before calling on a respondent.  Discuss conduction:  heat transfer between substances that are in direct contact.  

  3.  Convection:  

  • Lastly, once the water begins boiling, have the students come close enough to see and hear the water boiling.  USE EXTREME CAUTION AROUND THE HOT PLATE.   Ask the students what form of energy transfer is occurring now.  Again, call on a student who doesn't respond immediately.  
  • Discuss convection.  What evidence do they have that convection is occurring?  (The boiling water.)  Have them think about this and discuss.  

  Closure

  • Review the definitions that students have learned for radiation, conduction, and convection.  
  • Depending on the literacy level of the class, students may be asked to individually write a few sentences about each of the demonstrations linking each to the appropriate form of energy transfer.  For students at a lower literacy level, this can be done as a class discussion by separating the class into 3 groups and having each group talk about one of the forms of energy transfer relating it to the appropriate step of the process of making tea. 

a cup of tea on an outdoor table

Variations

This activity has been written (including the defintions) for an elementary or early middle school class.  If it were utlized with a high school class, the related definitions should be at an appropriate level for the class.

NGSS Standards:

4th Grade 

Energy:   Energy can be moved from place to place by moving objects or through sound, light, or electric currents. (4-PS3-2),(4-PS3-3)

4th Grade- PS3.B: Conservation of Energy and Energy Transfer

  • Energy is present whenever there are moving objects, sound, light, or heat. When objects collide, energy can be transferred from one object to another, thereby changing their motion. In such collisions, some energy is typically also transferred to the surrounding air; as a result the air gets heated and sound is produced. (4-PS3-2),(4-PS3-3)
  • Light also transfers energy from place to place. (4-PS3-2)
  • Energy can also be transferred from place to place by electric currents, which can then be used locally to produce motion, sound, heat, or light. The currents may have been produced to begin with by transforming the energy of motion into electrical energy. (4-PS3-2),(4- PS3-4)

Middle School

PS3.B: Conservation of Energy and Energy Transfer

  • When the motion energy of an object changes, there is inevitably some other change in energy at the same time. (MS-PS3-5)
  • The amount of energy transfer needed to change the temperature of a matter sample by a given amount depends on the nature of the matter, the size of the sample, and the environment. (MS-PS3-4)
  • Energy is spontaneously transferred out of hotter regions or objects and into colder ones. (MS-PS3-3)

PS3.C: Relationship Between Energy and Forces

  • When two objects interact, each one exerts a force on the other that can cause energy to be transferred to or from the object. (MS-PS3-2)

PS4.B:  Electromagnetic Radiation

  • However, because light can travel through space, it cannot be a matter wave, like sound or water waves. (MS-PS4-2)

High School

PS3.A: Definitions of Energy

  • Energy is a quantitative property of a system that depends on the motion and interactions of matter and radiation within thatsystem. That there is a single quantity called energy is due to the fact that a system’s total energy is conserved, even as,within the system, energy is continually transferred from one object to another and between its various possible forms. (HSPS3-1),(HS-PS3-2)
  • At the macroscopic scale, energy manifests itself in multiple ways, such as in motion, sound, light, and thermal energy. (HSPS3-2) (HS-PS3-3)
  • These relationships are better understood at the microscopic scale, at which all of the different manifestations of energy canbe modeled as a combination of energy associated with the motion of particles and energy associated with the configuration(relative position of the particles). In some cases the relative position energy can be thought of as stored in fields (which mediate interactions between particles). This last concept includes radiation, a phenomenon in which energy stored in fields moves across space. (HS-PS3-2)

PS3.B: Conservation of Energy and Energy Transfer

  • Energy cannot be created or destroyed, but it can be transported from one place to another and transferred between systems.(HS-PS3-1), (HS-PS3-4)

 

Collage of energy transfer

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