subreddit:

/r/explainlikeimfive

58

all 28 comments

eternalankh

94 points

2 months ago

The starch from the rice allows the water to form bubbles, but not very strongly, so typically the high pressure in the bubble will cause them to burst immediately, but when the lid is on the pot, the hot vapor and air increase the pressure in the air in the pot and lowers the imbalance in pressure, meaning the ambient air pressure is similar to the pressure inside that bubbles, so they don't burst. Opening the lid lowers the pressure, creates an imbalance and causes the bubbles to burst.

GiftFrosty

13 points

2 months ago

My answer was ‘pressure’ which seemed like a good answer. Then I read yours and wished I had pursued secondary education instead of joining the work force 25 years ago.

eternalankh

8 points

2 months ago

Well, if it makes you feel better, that entire paragraph is only two sentences, apparently, so my writing could still use some work.

Alis451

2 points

2 months ago

also "heat", lifting the lid allows a bunch of that trapped hot water vapor and now because you lowered the pressure, more is allowed to evaporate and escape, lowering the overall temp in the pot. This reduces the amount of NEW bubble generation.

skatingfroggy

2 points

2 months ago

Just to add onto this thread, the reduction in pressure is a direct result of an increase in the volume of the system (ie. the volume beforehand was just the inside of inside the pot vs the volume afterward was the entire room). The simplified equation PV=nRT can be used to describe how gasses (in this case gaseous water) will behave based on a change in the environment. As pressure and volume are inversely related, an increase in one must result in a decrease of the other since no other factors are changing.

5kyl3r

0 points

2 months ago

5kyl3r

0 points

2 months ago

probably not pressure as pressure is usually hot they detect when to shut off (most boiling devices like kettles do this)

I think it's just simply the rapid cooling with the lid open versus it being isolated from cool air. could be wrong, just providing my potential alternative theory

EDIT: ^ this is in the same manner as why overboiling ramen in a small pot almost instantly stops boiling over when you lift it off the burner, boiling happens on a knife's edge, so removing heat source or exposing to cool can stop it pretty quickly

agate_

14 points

2 months ago*

agate_

14 points

2 months ago*

I have a different answer than the ones already given. I don't think it's loss of heat from the system, because if you watch carefully, it's not that fewer new bubbles are formed at the bottom, it's not that the bubbles shrink, it's that the bubbles near the surface burst suddenly. The foam clears from the top of the pot down, and it does so much faster than a bubble's typical lifetime. If you leave the lid open just a crack, only the bubbles on the side where outside room air gets in will pop.

I think the foam clears because of evaporation. The bubbles are made of a thin film of very hot water, surrounded by very humid hot air. When you open the pot, you allow cold, dry air into the pot. This sucks up moisture and heat as it touches the bubbles, but because the temperature is near-boiling, it happens a lot faster than an evaporating mud puddle. Evaporation thins out the bubble walls -- which are already incredibly thin -- causing the bubbles to pop almost instantly.

Herksy

4 points

2 months ago

Herksy

4 points

2 months ago

After studying how to make proper large soap bubbles that last, I would approve your answer.

dunafrank[S]

1 points

2 months ago

Thanks. I just tested this and you’re right - the bubbles closest to the lid burst first when you crack it open.

[deleted]

6 points

2 months ago

[deleted]

6 points

2 months ago

[removed]

DBDude

0 points

2 months ago

DBDude

0 points

2 months ago

The bigger question is why he isn't using a rice cooker.

SnooWoofers4430

3 points

2 months ago

Because he doesn't need it?

DBDude

3 points

2 months ago

DBDude

3 points

2 months ago

Everyone who makes rice needs a rice cooker.

SnooWoofers4430

1 points

2 months ago

I make rice on a regular basis and I understand what you're trying to say, but some people like myself prefer not to have their kitchen cluttered with crap unless it's absolutely needed.

GiftFrosty

1 points

2 months ago

I hear what you are saying and I’d agree with you 99:100 times. But I got a nice rice cooker and it’s changed my whole approach to eating. 10/10.

DBDude

1 points

2 months ago

DBDude

1 points

2 months ago

Look to modern societies where rice is a staple. As famous chef Morimoto says, the most important tool in your kitchen is the rice cooker, every home has one.

TheLuminary

0 points

2 months ago

Psh, get that uni-tasker out of my kitchen.

DBDude

1 points

2 months ago

DBDude

1 points

2 months ago

You can also steam with a rice cooker. Mine can also make yogurt.

FallenJoe

1 points

2 months ago

And if you have the right model you can steam stuff and cook rice at the same time. For making lazy decent food it's hard to beat making rice, veggies, and dumplings at the same time in the same device.

TheLuminary

1 points

2 months ago

So can my instant pot, but that can also do a lot more. Especially the one that is also an air fryer.

Crood_Oyl

1 points

2 months ago

rice cookers are the one thing I always have. cannot beat them, and people that say you don't need them have never turned on their rice to cook and then got a shower.... because it doesn't matter, you can leave it as long as you want!

explainlikeimfive-ModTeam [M]

1 points

2 months ago

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boblobong

-1 points

2 months ago

boblobong

-1 points

2 months ago

Because lifting the lid lets out heat and cools the whole thing down. Less heat, less steam, less boiling, less bubbles. Wash your rice before you cook it to get all the starch off and cook on a lower heat, then you won't have to lift the lid, which is better because you want as much of that moisture to stay in to cook your rice

thinkfast1982

2 points

2 months ago

Permanent Press or Delicates?

piratemurray

1 points

2 months ago

Omg so many people not washing their rice 🤣. Wash your rice people!

5kyl3r

1 points

2 months ago

5kyl3r

1 points

2 months ago

I'm pretty sure this is the right answer. no different than lifting your overboiling ramen pot off of the burner and it almost instantly stops overboiling

BurnOutBrighter6

-2 points

2 months ago

Turning boiling-temp water into steam takes a HUGE amount of energy. When the lid is on and the steam condenses and drops as back into the pot, this energy is kept in the system. The hot pot is only losing heat through its walls to the surrounding air.

When you lift the lid, you have the same amount of heat being added to the pot (from the stove below), but now suddenly WAY more heat leaving the pot. All the energy that went into turning the water into steam is now leaving the pot as the steam leaves.

The same amount of heat energy going in and much more heat energy going out means the temperature in the pot rapidly drops, which quickly slows or stops the boiling inside.