|
To assess your students understanding of what a thermometer tube is and
how it is used, ask them to describe what they have observed:
- What happened as the thermometer tube was placed in each of the four
containers? (The level of the liquid in thermometer changed. It was
highest in A and lowest in B.)
Help your students understand that the warmed liquid takes up more room
inside the tube. (When warmed, the liquid expands. That's the way a
liquid-filled thermometer works, whether immersed in liquid or hanging
in the air. The red coloring is added to make it easier to see.) The
thermometer tube provides a reliable way to judge temperature that does
not depend on the sense of touch, which can be unreliable under some circumstances.
Back To Top
|
|
Complete this investigation by asking your students to reflect on its
investigation question and how their answers may have changed as a result
of what they have learned. While our sense of touch allows us to put things
in a relative sequence from warmest to coolest, as the differences in
temperature become smaller, our sense of touch can be less reliable than
an instrument. When we are in situations where we cannot use touch, some
kind of instrument must be used.
To help make the point about the sense of touch being unreliable, send
one student out of the room for a few moments while you prepare the following
demonstration. On a table where all students can see, set up three containers
of water that are large enough for a student to place her hand in:
- a container of water that is very warm (but not hot) to the touch,
- a container of water that is very cool to the touch,
- a container of water that is room temperature.
Cover the containers with a towel so they are not visible. Have the student
return from the hallway and blindfold her. Explain that she is going to
put one hand in warm water and the other in cool water, then you will
help her move each to another container. Guide the student's hands into
the warm water and the cool water. Then, one at a time, guide her hand
into the room temperature water and ask her to describe it to the class.
When she moves from the warm water to the room temperature water, she
will describe it as cool. When she moves from the cool water to the room
temperature water, she will describe it as warm. Touch is a relative sense,
in that we sense the difference in temperature between our current sensation
and the new one, not the absolute temperature.
Back To Top
|
