Measured temperature vs. anticipated

Materials:

• Alcohol thermometers
• Frying pan
• Portable stove
• Heat resistant crystal glass or porcelain cup
• Latex gloves
• Rubber bands
• Water
• Hot plates
• Scissors

Demonstration:

1. The teacher must warm up an empty frying pan. NOTE: The students must not notice it.

2. The teacher will show the frying pan the students.

a. What do you observe?

b. Can you say if the pan is hot by only looking at it?

3. The teacher will spill water at room temperature into the frying pan. NOTE: The frying pan must be hot enough - approximately 100°C - so that the water evaporates when it touches the frying pan.

Procedure:

• Organize the students in sub-groups and have them look for the materials (all except the frying pan and the portable stove).
• The students will fill the crystal glass or cup with water and will apply heat to it. Warning: The students in charge to warm up must have much precaution when making this step.
• When the water boils, have them take the temperature reading.
• The students now discard the hot water, in a bucket - indicated by the teacher - or by the drainage.
• Cut two fingers of a latex glove.
• Make the following assembly:

• Suck out the greatest amount of air than you can through one of the fingers of the glove it and tie the finger so that no air can enter.
• Place the thermometer through the other finger of the glove.
• Warm up the water until it boils.
• Read the thermometer for your companions.
• The measured temperature is always correct whereas the anticipated one may be mistaken.

Discussion: State the following questions.

1. During the demonstration, you can identify when an object is hot? Please explain.
2. To which temperature does the water regularly boils?
   
3. To which temperature did the water boil?