
title: Notes  Tutorial 25
layout: page
parent: Tutorial Notes
date: 20200810
lesson: 25

## why do pots get empty when you boil water
if you put a pot of water oh a hot plate the pot will become empty.
it takes a little bit of time because the water is heating up.
when the water gets really hot it will start bubbling.
it will keep bubbling till there's no water left and the pot is empty.
where does the water go and why?
when the hot water is making the bubbles  what we call boiling  it means the water is turning into steam.
steam is water that's a gas, which means its not a liquid any more.
that means it goes into the air, sort of like rain in reverse.
after it boils the steam is still very hot, so it's not good to breath it in because it will burn you, like hot water will.
when water is a liquid it sits in the bottom of the pot with a flat top and no gaps around the edges, but it doesn't do this if it's a solid or a gas.
if it's a solid it will stay in one shape, like when it's an ice cube.
if you put solid water (ice) in a pot you'll notice that it doesn't sit in the bottom like when it's a liquid does.
it stands up and there are gaps around the edges.
when water is a gas it doesn't sit in the bottom of the pot, either.
but instead of being in one solid block, like when it's frozen, the water splits up into tiny bits we call molecules.
these water molecules mix in with the other molecules in the air as the water boils.
if you could collect all the air from around the pot and cool it down you could get the water back.
some of it will probably escape, though.
paragraphs i cut:
water doesn't just have to be a liquid or a gas, it can freeze and become solid too.
if you hold that water in your hand it will melt and become a liquid again.
this is because you're heating it up.
all matter can be solid, liquid, or gaseous, but it happens at different temperatures depending on what it is.
if you have a solid and heat it up, it will melt and turn into a liquid.
if you have a liquid and heat it up, it will boil and turn into a gas.
solids melt into liquids, and liquids boil (or evaporate) into gases.
this goes the other way too.
if you cool a gas down it will condense into a liquid.
and if you cool a liquid down it will freeze into a solid.
some chemicals are special, and go straight from being a solid to a gas, without being a liquid in between.
when a chemical does this, we call it sublimation; the solid sublimates into a gas.
if it goes the other way, where the gas becomes a solid, we call it deposition (or desublimation); the gas deposits into a solid.
q
1. inappropriate to be introducing new terms like 'chemicals' or 'molecules'?
2. problem: getting in to a 'explain everything' mode where i go too deep
## why does a mirror show an image of yourself? (one paragraph)
a mirror shows a reflection of yourself because, when you're standing in front of it, light is bouncing from you to the mirror then to your eyes.
if you put a camera in front of the mirror and take a photo when you're not there, the photo won't show you in the mirror, it'll show the camera.
in this case, light from the camera is being reflected by the mirror back to the camera sensor which is recording the image as a photo.
if you look at that picture later you can still see the mirror (especially if the photo captures the frame) but you're seeing what the mirror was reflecting at that point in time: the camera.
if you're standing in front of it, you're seeing the thing it's reflecting at that point in time, which is you.
## notes
 consider goal
 what does each sentence do to help the goal
 what does it talk to
 what does audience already know / what do they need to be told
 preaddress common qs
 article needs to be consistent with goal, and internally consistent
approach:
 brainstorm ideas that could be included
 when someone learns the truth will they be surprised or feel betrayed; will it seem like a lie?
 was anything left out that seems important?
 any inelegancies that need cleaning up?
## why do pots get empty when you boil water
> if you put a pot of water oh a hot plate the pot will become empty.
> it takes a little bit of time because the water is heating up.
 can mislead ppl, "some time" better than "little", "time" better still
 assuming context that isn't written down
> when the water gets really hot it will start bubbling.
 vague
> it will keep bubbling till there's no water left and the pot is empty.
> where does the water go and why?
> when the hot water is making the bubbles  what we call boiling  it means the water is turning into steam.
 not linking hot water > bubbles > steam
 link internal and external process
> steam is water that's a gas, which means its not a liquid any more.
 not relevant, sort of contradicts
> that means it goes into the air, sort of like rain in reverse.
> after it boils the steam is still very hot, so it's not good to breath it in because it will burn you, like hot water will.
> when water is a liquid it sits in the bottom of the pot with a flat top and no gaps around the edges, but it doesn't do this if it's a solid or a gas.
 conceptual jump to geometric description
 can misread modifiers as applying to pot not water

> if it's a solid it will stay in one shape, like when it's an ice cube.
> if you put solid water (ice) in a pot you'll notice that it doesn't sit in the bottom like when it's a liquid does.
> it stands up and there are gaps around the edges.
> when water is a gas it doesn't sit in the bottom of the pot, either.
> but instead of being in one solid block, like when it's frozen, the water splits up into tiny bits we call molecules.
> these water molecules mix in with the other molecules in the air as the water boils.
> if you could collect all the air from around the pot and cool it down you could get the water back.
> some of it will probably escape, though.
### attempt
Water boils when you make it hot.
When it heats up some tiny bits of water get hotter than the other bits.
When tiny bits of water get hot enough they jiggle around so much that they turn into a gas.
If those bits are on top they go straight into the air.
If those bits aren't on top they still become a gas, but because they're under the rest of the water they turn into bubbles.
These bubbles aren't air bubbles, they're steam bubbles.
When something is a gas it means the little bits are jiggling so much they don't stay in one spot, and instead float around.
Eventually, all the water gets hot enough to have gone into the air and there's none left in the pot.
### mirrors flip horiz
### what is division
goal:
 explain what division is
 so that someone who knows about adding, subtraction, or multiplying can understand
 but doesn't yet know about division
brainstorm:
 numbers are made of other numbers (factorization)
 whole numbers and fractional numbers
 "blocks" of numbers; geometric interp. of multiplication
 is there a better way to put this?
 multiplication  repeating X times
 division is breaking up numbers into some number of equal parts (some number => divisor)
 the answer to a question of division is how the size of the parts you get
 geometric: 'size' and number of chunks
 multiplication (Z = X * Y) is how big the final thing is when you have X chunks of Y size
 division (Z / Y = X) is how many chunks you have if you make chunks of size Y from a total Z
 can't divide by 0
 anything divided by 1 is itself
 opposite of multiplication
division and multiplication are inverse operations.
multiplication combines a certain number of chunks of a particular size into a total.
division breaks up a total into chunks of a particular size and you get the number of chunks as the answer.
division is the opposite of multiplication.
division is breaking something up into parts of equal sizes.
 how big is the thing? how many parts? how big are the parts?
multiplication repeats the selfaddition of a number a certain number of times.
multiplication is repeated addition. particularly, it's adding the same number over and over again. how many times do we add it? n times.
multiplication is repeated addition of the same number a certain amount of times.
when we multiply two numbers, it's like taking an area the size of the first number, but we have n of them instead.
when we divide a big number by a smaller number we're asking: if we break the big number into chunks the size of the small number, how many chunks do we get?
an example is cutting up a pizza.
if we *divide* the pizza into 8 parts, the answer to the question of *division* is how big the slices are.
to go the other way, we could take one slice and *multiply* it by 8 to get the whole pizza back.
the act of *dividing* the pizza breaks it up into smaller parts (of equal size).
if we have 8 slices of pizza and 4 people, how many slices does each person get?
trial and error: we can figure this out by guessing how many slices people get and multiplying it by the number of people, and if we get 8 slices total we know the answer.
but we could also divide 8 slices by 4 people, which would give us 2 slices per person.
we broke the number 8 into 4 equal chunks, and each chunk was 2 slices large.
if we have 8 slices of pizza and 4 people, how many slices does each person get?
we have 8 slices and we need to give each person equal parts of the pizza.
since we have 4 people, we *divide* 8 slices by 4 people, which would give us 2 slices per person.
division is breaking something up into some number of chunks of equal size.
the answer to a division question is how big the chunks are.
division is breaking stuff up into groups of equal size.
e.g. if we have 8 slices of pizza and 4 people, how many slices does each person get?
we *divide* 8 slices by 4 people to get the answer: 2 slices per person.
we've divided the pizza, which was 8 slices large, into 4 chunks of 2 slices each.
if someone asks: "what's 8 divided by 4?" then they want to know the size of the groups if there are 4 groups and 8 things total. the answer is 2  which we saw with the pizza.
we can check this by multiplying 4 people by 2 slices each, and we get 8 slices total so it works out.
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