Heat in a water bath and keep the cover on
The note says the bath has to be hot AND humid, and the cover goes back immediately. Learn what each of those words is holding in and what a quick look costs.
- Water sets a ceiling on temperature: Water in an open container will not climb past its boiling point however long you heat it. That makes a water bath a heater with a built-in limit.
- Moist air escapes as soon as you open the box: The humid air above a warm bath is held in by the cover. Lift it and that air is gone in seconds, taking the humid half of the condition with it.
Prerequisites are inferred: pending teacher review.
Re-learn the skill with worked practice and clear examples.
Now count the cost of a quick look, and get the tray out without a burn.
A student lifts the cover twice during the 60 seconds to check on their slide. What have they changed?
Reviewed- A.The temperature of the slide, which drops below the water temperature
- B.The timing, which now has to be restarted from zero
- C.The humid air is let out each time, which is half the stated condition
- D.Nothing that can be measured, since the water underneath is still just as hot
Show the worked solution ▾
Answer: C. The humid air is let out each time, which is half the stated condition
- Step 1: Ask which of the two conditions survives an opening: The water stays hot. The moist air does not.
- Step 2: Ask how long it takes to leave: As long as it takes to lift a lid.
Why it's right: The heat is stored in a bath of water and barely notices. The humidity lives in the air above it and leaves the moment the box is opened, so the half of the condition the note capitalised is the half a look destroys.
- A: The slide sits in the same warm space and does not drop below the bath. What changes around it is the moisture, not the temperature.
- B: Nothing in the procedure says to restart the timing, and the real loss is the conditions during that minute rather than the count.
- D: The water is unaffected, and that is exactly why people think a quick look is harmless. The other half of the condition is not stored in the water.
Aligned to Handling, Preparation, Storage and Disposal · reading level ~grade 9
How should the tray come out of a hot, humid water bath?
Reviewed- A.With whatever heat protection you have been given, and away from your face
- B.Quickly with bare fingers, since 60 seconds is not long enough to get hot
- C.After the bath has been switched off and left to cool for a few minutes
- D.By tipping the bath so the tray slides out towards you on its own
Show the worked solution ▾
Answer: A. With whatever heat protection you have been given, and away from your face
- Step 1: Ask what comes out with the cover: A rush of hot moist air, upward, toward whoever is leaning over it.
- Step 2: Ask what the tray has been sitting in: A hot bath, so it is hot too.
Why it's right: Two things are hot: the tray and the air that leaves when the cover lifts. Heat protection deals with one and keeping your face back deals with the other.
- B: A minute in a hot bath is plenty to bring a tray up to the bath's temperature, and the slide is what stops being useful if it gets dropped.
- C: Waiting would be safe, and the slide has a 60 second exposure, so a step that is finished cannot be left in the bath while it cools.
- D: Tipping a bath of hot water toward yourself is a much larger version of the hazard you were trying to avoid.
Aligned to Handling, Preparation, Storage and Disposal · reading level ~grade 9
- A student opens the bath with the lid angled away from their face.
Fill these in as you work through the lesson.
- Water bath (even heat with a ceiling on it):
- Humid (the second half of the stated condition):
- Cover (what keeps the moist air inside):
- Incubate (hold at conditions for a stated time):
The bath has to be hot humid. Replace the immediately, because the moist air leaves the moment it is open. Incubate for seconds, then let the slide for five minutes.
- Say what a water bath does that a hot plate does not.
- Explain what is lost each time the cover comes off.
- Describe how a tray comes out of a hot bath.
You place the tray in, put the cover straight back, and start the timer. You do not open it to check at thirty seconds, because the slide would then spend the second half of its minute in room air.