Lab 11 Desalination of Ocean Water by Distillation

over 70% of the earth's surface is

covered with water but most of that

water salt water in the oceans only a

very small amount of that water is

actually freshwater and most of the

fresh waters locked up as glaciers and

some of it's in our lakes and only a

very small amount is in our streams and

in groundwater and that's the water that

we rely upon as drinking water the

leading cause of death of children in

the world is lack of clean water

so can we take salt water and turn it

into fresh water that's the purpose or

objective of this lab to take salt water

and run it through a process called

distillation and distill it into fresh

water process of distillation is very

energy intense we're gonna need a Bunsen

burner for this lab we're gonna need

obviously a lighter to start the Bunsen

burner you'll need a 250 milliliter

Erlenmeyer flask with a rubber stopper

and a tube coming out of it that's going

to collect the steam and you're gonna

need a test tube in order to condense

the steam into liquid water you'll need

a six hundred milliliter beaker some ice

a couple boiling chips or rocks labquest

device and a conductivity probe to

measure how much salt is in the water

and of course you'll need salt water in

order to run this experiment as well to

your 250 milliliter Erlenmeyer flask go

ahead and add a small handful of rocks

and those are gonna be boiling chips

that are gonna allow the salt water to

boil at a normal amount without over

boiling to the Erlenmeyer flask also add

100 milliliters of salt water

replace the cap on the ER in my

Erlenmeyer flask make sure that the tube

the rubber tube is going to travel

continuously down without having a bend

or a kink in it where the water can

start to build up that can be kind of

dangerous so make sure it's a normal

line going all the way down into a test

tube which is in this test tube has to

be extremely clean because our gonna be

collecting clean pure distilled water so

make sure that this is very clean if not

make sure to rinse it out a bunch of

times with distilled water and collected

in a 600 milliliter beaker that contains

an ice water bath so this beaker should

contain ice and water to make an ice

water bath okay so there's your ice

water bath go and put the test tube in

the ice water bath before you start the

experiment you're going to measure how

much salt is in that water I made up the

salt water to contain 8 grams per liter

now let's use our conductivity probe to

measure and see how much exactly is in


plug your conductivity probe into the

labquest device over at all rinse the

conductivity probe with distilled water

the tip of the conductivity probe the

very end of it rinse it with distilled

water only ever use distilled water

if the distilled water ever runs out

make sure to only fill it up using the

distilled water in this container and

not to fill it up from the sink so that

these always only contain distilled

water purified water

place the rinsed conductivity probe

directly into the salt water make sure

that the tip of the temperature

conductivity probe is completely

submerged right now it's not so what I

need to do is tilt this a little bit so

that the conductivity probe is

completely submerged

make sure the toggle switch on the

conductivity probe is on the zero to

20,000 reading this is because we're

measuring salt water and salt water is

going to have a high reading so we're

not going to use either the lower

readings will use the highest reading on

the labquest change the units to

milligrams per liter change the units to

milligrams per liter I said before that

I made this salt water as a 8 grams per

liter that would be 8,000 milligrams per

liter this is reading 7215 that's

probably pretty accurate simply record

the live readout in your data table so I

would write 7 to 1 5 milligrams per

liter in my data table you do not need

to connect your iPad to the labquest for

this experiment carefully remove the

conductivity probe from the salt water

over at all rinse the salt water off the

conductivity probe using distilled water

set the labquest aside you won't need it

until you've completed the experiment

reset your Erlenmeyer flask

put the cover back on put on a sweet

pair of goggles now it's time to light

and adjust your Bunsen burner so first

thing you want to do is connect the

Bunsen burner tube to the gas turn the

valve on go ahead and light your Bunsen


so this flame looks pretty good but I'm

gonna show you how to make a couple

adjustments in case it doesn't look so

good when you first turn it on first of

all I'll show you that there's two

adjustable things you can do one is that

you can turn this and by turning that

it's going to reduce or increase the

amount of oxygen that's going into this

thing alright so if you find a really

orange flame that's this is what you

need to adjust either just the base here

get it back down so you have basically a

flame within a flame you've got the

inner blue flame and the outer blue

flame and should be about a one-inch

flame there and about a two and a half

inch flame there if you're not getting

enough flame you can do one of two

things you can make this adjustment on

the base here

maybe that's it maybe that's reducing

how much gas is coming out by increasing

this you're increasing how much gas is

going through and that's way too much

again you just want kind of a normal

flame there so again that looks pretty

good I'm gonna be happy with that just

wanted to show you some adjustments

quick on the Bunsen burner go ahead and

begin heating your saltwater making sure

that everything looks good okay this

tube should be going all the way down

without any kinks in it all the way into

your clean collection test tube which is

in the ice water bath you want kind of a

nice medium controlled flame so that

things don't get out of hand if they do

get out of hand and this boils over too


you're gonna contaminate your test tube

and what you're gonna want to do right

away is if things get out of hand too

quick the first thing to do is probably

just to move the Bunsen burner out from

underneath the flask then obviously then

you can start taking time and making

adjustments on the flame so things are

going pretty well I've got a pretty good

rolling boil here just be careful that

you don't want it to boil all the way up

to the rubber stopper or you're gonna

start to get salt water in there so

again you can you can make some minor

adjustments on the flame to make sure to

keep it down so that you're not going to

get too hot of a boil I'm just a normal

boil you can see it this is I'm kind of

zooming in on the test tube inside the

beaker that you can see that the level

is rising I'm collecting

distilled water as it boils here slowly

but fast enough that you can observe it

happening here and we're condensing the

steam into into water here a nice

water bath again just be very careful

this is a potentially dangerous

situation so please just don't sit on

your iPad and play games obviously you

never want to do that but this is this

is something you need to keep an eye on

here this is we got very hot steam we've

got boiling water here we've got a

potential pressure situation if this

gets backed up so just make sure you're

monitoring this the entire time it's

happening when it looks like you've got

you know just don't water collected in

your test tube go ahead and shut off the

flame by turning the valve off don't

just blow it out here the gas will still

come out now what we really want to do

is get a reading on what's the

conductivity of the distilled water so

again don't you might burn yourself if

you grab that just be careful and we

want this to be in room-temperature

water no ice water so I grabbed another

beaker I'm going to fill that up with

carefully so that you don't burn

yourself transfer your distilled water

into that room temperature water when a

few minutes have gone by place the

conductivity probe inside the distilled

water test tube since we're reading

distilled water you really need to

change this setting okay so this should

no longer be 0 to 20,000 we're checking

distilled water that's probably gonna be

a pretty small amount of salt in there I

probably change it to the lowest setting

which is 0 to 200 for this reading make

sure that your units are in milligrams

per liter and I'm now reading 11.5

milligrams per liter where we're reading

in the 7000 before so yeah we definitely

purified and distilled the water the

salt water and obtained some very fresh

pure distilled water clean up make sure

to rinse off your conductivity probe one

more time and dry it off before you put

it away like always rinse out test tubes

and beakers I just recommend at least

rinsing them thoroughly five times to

make sure you get any salt or anything

like that off of them certainly allow

your Erlenmeyer flasks to cool for a

long time before you touch it please

take your time cleaning up lab equipment

rinsing off glassware and spraying off

your table Thanks