Add option for water to the combobox

arouinfar commented 5 years ago

Suggestion from Argenta, who has been using this sim in a study (emphasis added):

I've been working on writing a paper about all the interviews I did with students using PhET sims. Since I used the pH scale sim the most, I've been focusing a lot on that (though I'll also talk some about other sims). I was just writing about the interaction between students' perception of the task and their prior knowledge, and in pulling examples of the points I wanted to make, I realized that there's a really common stumbling point for most students having to do with how exactly adding water changes the pH of a solution. The students who successfully come up with a reasonable explanation either already know that water has equal numbers of hydroxide and hydronium in it, or they decide to explicitly test water. And often they don't test water unless I later ask them what water would look like by itself. I think a fair number of these students would have tested water on their own if it had been in the drop down menu (I have examples of their going to look for water in the drop down menu, then giving up when it's not there). The sim does have the tools they need to test water, but it's just not obvious for many of them.

So, since whether or not they look at water alone seems to be one of the main actions I'm seeing as differentiating between students, I was wondering if it was an intentional choice not to include water in the drop down menu, and if you'd consider adding it in (at least on the micro tab)?

@kathy-phet and I think Argenta provides a pretty compelling case to include water as an option in the combobox. While it's true that students can empty the beaker and then fill it with water from the FaucetNode, it appears that few take this path. I see no real disadvantage to including water in the combobox.

For consistency, I would include add water to the combobox on both the Macro and Micro screens. Since it appears that the combobox items are ordered by pH, water would be between spit and milk.

@pixelzoom any thoughts or objections? I don't think this is a particularly time sensitive change request, so feel free to unassign for now.

pixelzoom commented 5 years ago

It's trivial to add Water to the combo box. Just add Solute.WATER to Solute.js, then add Solute.WATER to the list in MacroModel.js (which affects both the Macro and Micro screens). Here's the code:

// Solute.js
  Solute.WATER = new Solute( Water.name, Water.pH, { stockColor: Water.color } );

// MacroModel.js
    this.solutes = [
      Solute.DRAIN_CLEANER,
      Solute.HAND_SOAP,
      Solute.BLOOD,
      Solute.SPIT,
      Solute.WATER,
      Solute.MILK,
      Solute.CHICKEN_SOUP,
      Solute.COFFEE,
      Solute.ORANGE_JUICE,
      Solute.SODA,
      Solute.VOMIT,
      Solute.BATTERY_ACID
    ];

A few things to consider:

All of the things in the combo box are solutes, and water is the solvent. Having water as both the solvent and solute doesn't seem to break anything, but there are some quirks. Like...
In the Macro screen, when you drain all of the solution out of the beaker and add Water via the faucet, "Neutral" appears in the beaker. That doesn't currently happen when Water is selected in the combo box and the beaker autofills (I tried it). That can be changed, but there may be unknown issues.
Is it confusing to have Water in both the dropper and the faucet?
Whatever we do to pH Scale also appears in pH Scale: Basics.

pixelzoom commented 5 years ago

Note to self about this issue:

In the Macro screen, when you drain all of the solution out of the beaker and add Water via the faucet, "Neutral" appears in the beaker. That doesn't currently happen when Water is selected in the combo box and the beaker autofills (I tried it). That can be changed, but there may be unknown issues.

This is easily fixed. In NeutralIndicator.js, change this:

    solution.pHProperty.link( function() {
      self.setVisible( solution.isEquivalentToWater() );
    } );

...to this:

    solution.pHProperty.link( function( pH ) {
      self.setVisible( pH === Water.pH );
    } );

arouinfar commented 5 years ago

Thanks @pixelzoom.

In the Macro screen, when you drain all of the solution out of the beaker and add Water via the faucet, "Neutral" appears in the beaker. That doesn't currently happen when Water is selected in the combo box and the beaker autofills (I tried it). That can be changed, but there may be unknown issues.

This is easily fixed. In NeutralIndicator.js, change this:

Seems like you've figured out a solution to this, so let's try it out.

Is it confusing to have Water in both the dropper and the faucet?

I don't think so. Argenta found that several students explicitly looked for it in the combobox. It could also bring up a broader solute vs. solvent conversation in a classroom, which could be valuable. While water is often the solvent in a solution, it can be the solute, which is the case in high-proof alcohol (> 100 proof).

Whatever we do to pH Scale also appears in pH Scale: Basics.

Got it. I don't see why this change couldn't apply to both sims.

arouinfar commented 5 years ago

Can you push these changes to master so I can test it out?

pixelzoom commented 5 years ago

@arouinfar Changes have been pushed to master and published in 1.3.0-dev.4.

arouinfar commented 5 years ago

@pixelzoom the behavior is looking good to me!

I can't speak to what the timeline should be for this change to get published, other than I'm fairly certain it would be somewhat low priority. When time allows, it might be nice to send this sim through QA to pick up LoL support. @kathy-phet @ariel-phet thoughts?

pixelzoom commented 5 years ago

It's up to @ariel-phet to decide when to put ph-scale and ph-scale-basics into the QA pipeline. They should be done together.

They are ready to start RC testing at any time. There are no outstanding issues, and only 2 enhancements have been made -- see https://github.com/phetsims/ph-scale/issues and https://github.com/phetsims/ph-scale-basics/issues.

The 1.2.x release branch was first published ~11/17/2015, so it's been a long time (pre chipper 2.0?) and there are undoubtedly many common-code upgrades to be picked up, as well as LoL support.

kathy-phet commented 5 years ago

And will also pick up LoL support.

ariel-phet commented 5 years ago

I think probably when I get back from Japan, a fair number of things in QA right now. Tentatively plan 1st week of April @pixelzoom

KatieWoe commented 5 years ago

Looks good in both rcs

phetsims / ph-scale

Add option for water to the combobox #75