Tina, don't listen to the naysayers :)
You absolutely can write a realistic scenario that accomplishes everything you are asking in the context of a high school chemistry class. The only thing is that we need a bit more information about your context and your aims. For example:
In what historical era and location is your scene going to play out? The reagents available in a 2017 public high school chemistry class will be very different from what was available in a public high school in 1965.
How risky / dangerous do you want this to be? Do you want this to be a normally safe and common activity that goes wrong because of clumsiness or tomfoolery, or do you want this to be something slightly dangerous or perhaps even very dangerous, so that both teacher and students are warned and ready to respond when something goes wrong?
This guide for high school teachers comes from the American Chemical Society and it gives a lot of specific information that may be helpful to you.
Do you want the student to put herself under the safety shower? Current published guidelines for high school chemistry classes say students should be taught to walk quickly but calmly to the shower and pull the handle immediately under certain circumstances. For example, the ACS guide says this:
Students should be taught the “stop, drop, and roll” technique to be used if their clothes catch on fire elsewhere, and in the laboratory taught to walk calmly to and use the safety shower to extinguish clothes that are on fire. A drill to practice these exercises is recommended.
If you do not want the student to be forced to undress completely, perhaps a spill resulting in a small clothing fire (with or without burned hair) might accomplish all of your goals. If that would do, I suggest that you could have the students be performing metal salts flame tests using the petri dish technique, in which metal salts are burned in a small amount of methanol (methyl alcohol) and the material is identified by the rainbow of colors that are observed in the flame. This would be a great visual when your book is made into a movie :)
Here is a link to a middle school guide for one version of the flame test. Having a small spill of burning alcohol cause clothing to catch fire is quite realistic. Most such events are easily handled, but the risk is real and the safety shower, while not the best approach for significant amounts of burning liquids, would absolutely work to put out a clothing fire ignited by a small amount of flaming alcohol.
I should point out that over the years there have even been a few published classroom incidents in which poor ventilation caused a large amount of methanol fumes to accumulate and a massive fireball resulted. There are some people who feel the flame test should not be part of a modern curriculum, but is is widely performed, colorful, fun for students, teaches something quite fundamentally important both in chemistry and in physics, and falls well within a safety zone appropriate to this age group. You can purchase a kit here and elsewhere.
Because links may evaporate, I will embed a description of a flame test involving methanol in a petri dish:
Description: Methanol solutions of salts are burned to observe that
different wavelengths of light are emitted by different materials
- Petri dish
- Cover (to extinguish flame)
- NaCl (yellow)
- SrCl2 (red)
- LiCl (red)
- KCl (violet)
- CuCl2 (green)
- CaCl2 (red-orange)
- H3BO3 (green)
Several variations exist including the “Petri dish” method (described
here), the squirt bottle method (ref 1), the H2 balloon method (ref.
2), the guncotton method (ref 3) and the Magic Eraser method (ref 4).
Sprinkle a spatula full of each salt into separate Petri dishes.
Cover salt with methanol (10 mL). Turn off the lights for a better visual effect. Use the lighter to start up the flame for each sample.
To extinguish the flame, put the cover over the Petri dish and let cool before removing.
Discussion: When an element is burned, the electrons are excited. As
the electrons from an excited state relax back to a ground state, they
will emit photons of light. These photons will have different colors
depending on the element and its discrete energy levels. That is,
different wavelengths of light (colors) will be emitted when the
electrons of different elements go down the step(s) between their
energy level(s). Each element will have its own set of steps therefore
each will have its own color.
Safety: Wear safety glasses and goggles while preparing and during the
demonstration. Be sure to allow time for the cover to cool before
And here's what it looks like:
If you prefer a chemical spill that causes the teacher to put your student under the shower, that is also easily accomplished in a high school chemistry class. Somebody has already suggested that if a chemical spill occurred the student would be undressed before entering the shower. This is not correct: the ACS high school chemistry teachers guide I referenced above says about corrosives:
If splashed on clothing, the clothing must be
removed while under a safety shower. Do not remove the clothing and then get
under the shower. While under the shower, remove all clothing, including
shoes, socks, wristwatch and strap, and other jewelry if they are splashed with
corrosives (this is no time for modesty). Stay under the shower for at least 15
minutes while someone else calls a doctor.
Most safety showers are fully exposed, but there are times when they may be located in an alcove with a door that can be closed or a privacy curtain that can be pulled across. There are also safety showers with built-in plastic curtains that can be pulled around for privacy.
If you want the safety shower to be required for a chemical spill resulting from an experiment generally recognized as safe, then any of the mild corrosives will do but you will need to have the student be drenched with the material -- a small spill of most "safe" high school chemicals would not result in a full shower, and of course if ANY splash involves the face then the eyewash station would be the first thought. I've seen people fully drenched from the eyewash station, though, so perhaps that would fit your needs?
If you want to create real fear of injury from a minor chemical spill or splash, this can still be accomplished within a realistic high school setting. I'll pick just one example: it's not unknown for chemistry classes to have students etch mirrors using hydrofluoric acid, which in liquid form is one of the most noxious substances you can come into contact with anywhere below graduate-level chemistry. Even with immediate irrigation the stuff has a tendency to percolate into the body, and you will probably die despite treatment if a small glassful spills in your lap. For this reason it's not used at all as a reagent in high school. However, HF acid is one of the few things that will etch glass, and it is used in various forms for glass etching. The demonstration of an acid that can dissolve glass appears in chemistry courses even at the high school level. This stuff is so nasty that the slightest splash will cause immediate alarm. The correct response is immediate and prolonged irrigation and the immediate application of calcium gluconate gel as a neutralizing agent.
Here's a link to a college-level class guide in which liquid bath glass etching is performed, and if this were an AP class perhaps something like this might appear. Somebody is bound to comment that hydrofluoric acid would not be provided to regular high school students, and thankfully in a strict sense that's true. However, the stuff does still show up in high school classes in various forms. It's routinely found in high school electronics classes in the "liquid tin" solutions used for tin-plating the copper traces on printed-circuit boards, and that same reaction could easily be part of chemistry segment on metals. And here's a link to a fund-raising prospectus in which a high school chemistry teacher recently raised money so that inner-city high school students could "etch glass mirrors with hydrofluoric acid". The link includes photos of the students displaying their etched mirrors, one of which I will embed here.
Of course the material given to these students used was not a liquid form of HF even though it's billed that way -- it's actually a cream that contains fluoride salts. If washed off quickly enough it will cause only superficial injury (and ruin your clothes) -- but if there were any sort of splash you can bet the teacher would be rushing a student under the shower ASAP.
So if you want to create a real fear, the mere mention of hydrofluoric acid would do it. As a physician (board-certified in Emergency Medicine) I have treated several patients for exposure to hydrofluoric acid, including one unfortunate janitor who died a week later (despite rapid and aggressive treatment) after what initially appeared to be a minor splash from an unknown roof-cleaning chemical. It wasn't until we called the poison center to find out what was in that branded stripper/cleaner that we knew it was going to be bad, and even then it was hard to believe how bad. Believe it or not, all the area hospitals actually ran out of calcium gluconate supplies before he died, so yes, scary.
Lots of options for you, but in the end I think you'd be best served by the colorful flame test: put a Bunsen burner together with a spilled petri dish of alcohol and you get a lot of excitement, a quick trip to the shower, and the kind of damaged clothing and minor burns that people can easily understand. And no need for your student to disrobe.