Understanding Solids and Liquids: Key Differences and Properties

[Music] hi it's Mr Anderson and this is chemistry Essentials video 13 which is

on solids and liquids and we have solids and liquids right here uh water in a both liquid and solid phase um and so

when we're looking at solids and liquids it's almost easier to compare them so we're going to use a ven diagram so

we've got solids and liquids how are they alike well they're both made of matter they both have a specific molar

volume in other words they're close enough where their molar volumes are going to be about the same and they're

all going to be made of particles so is all matter but what's different between liquids and and solids is the

intermolecular forces are going to be slightly different between a solid and a liquid and so if we look at solids

they're going to be highly ordered and what that means is that their atoms are going to be locked into a specific

Matrix they can vibrate in fact they have to vibrate over time but as a result they really are two different

types amorphous and crystalline solids if we're looking at IDs they're more disordered and they can show what's

called translation where they can move around each other um and as a result they're going to be uh take the shape of

whatever container they're in and then they're going to be properties based on these intermolecular forces like surface

tension viscosity and volume of mixing that we talk about with liquids that we don't have to talk about when we're

talking about solids and so how do we look at these two and how they move from one into another well we can look at a

heating curve or if you just turn that around a cooling curve and it's going to show us the transition between the two

and so if we're looking at phases of matter it's first best to come up with some kind of a representation of what

they look like and so we're going to use a simulation here from pH at Colorado edu and so what we've got here is a

bunch of water in a solid phase and so you can see that they're locked in position and as we move it to liquid now

they can translate they can move around each other now this is not a great model of a liquid it should kind of flow down

to the bottom but at least we're seeing what's going on at the particle phase and then if we look at a gas as we

increase the energy again now they're moving all over the place and we'll talk about gases in the next video and so

what we're going to do is we're going to take some of that energy away we're going to take some of that heat away and

as we cool it down you can see here that we're measuring this in kelvin uh as we cool it down it turns into a liquid and

now it's into a solid you can see even at a solid phase those still we're seeing vibrations within there but as we

approach absolute zero all molecular motion is eventually going to come to a stop when we reach

that point okay so when we're looking at solids solids are going to have a specific uh Matrix in other words all of

the atoms molecules are going to be put together in a specific shape if it's a morphus there's not going to be a

repeating pattern to this and so this is a morphus right here so you can see it's made of silicon and oxygen but they're

going to be put together in all different shapes and as a result we get what's called a morphis quartz or

sometimes we call this glassy quartz and so it's going to be really brittle really easy to break and so some solids

like rubber for example is going to be an morph is solid doesn't mean that it's not a solid it's just not going to be as

an organized and if we look at crystalline structure like that in this crystallin uh quartz it's going to be

the same atoms you can see but they're arranged in a repeating pattern and now we get these beautiful crystals right

here it's going to be harder so a diamond for example is going to be something that would be uh in a

crystalline solid as we move into liquids what they can show is something called translation so that means that

let's say we have these water molecules right here they're not locked in those positions in other words they can

translate about each other and as a result liquids are going to take the shape of their container now depending

on the forces between those water molecules we're going to have different properties one of the first ones is

going to be viscosity viscosity is how easily a liquid is able to flow and so right here we've got a picture of pitch

pitch is going to have really high viscosity that means it really is going to flow at a real slow rate it's still

going to take the shape of the container you can see down here and so something that would have for example a real low

viscosity might be water it's going to easily flow um alcohol might be one that has low viscosity another property is

going to be surface tension surface tension is going to be based on the intermolecular forces in a liquid and so

these different molecules are going to be attracted to one another and they're also going to be attracted to one

another at the surface and so surface tension is going to be almost this layer of chemical attraction uh over the

surface of a liquid and so a water Strider like this is able to float on top of that surface tension if we were

to break the surface tension one way to do that would be to add something like soap it's going to break those

intermolecular forces and trust me that water Strider is going to quickly sink to the bottom of the lake and then the

last thing is called the volume of mixing and this is uh it's best easily understood if we use a demonstration

this is one that I use in my class imagine I were to take some pure water so we have distilled water and I were to

put it in a graduated cylinder and I were to be real precise and measure at exactly 250 ml of water I were then to

take some ethyl alcohol so ethanol and I were to measure out exactly 250 ml of that as well so let's say I'm very

precise I have 250 Ms of each what do you think is going to happen if we combine those two amounts together in

another graduated cylinder well when you do this if you have a large enough amount you're not going to get 500

milliliters and so that's weird it seems like it disappeared but really what's going on is the water and the alcohol

are able to fit within each other there's going to be room within there and so that's based on those

intermolecular forces as well if we were to combine water and water we' get 500 Ms but because we have less attraction

in those alcohol and molecules the water molecules can kind of get in there and so how do we look at that transition

from solid to liquid and back again we use something called a heating curve and so what we have down here is heat so

we're adding heat in this direction and then we've got the temperature on the side and the heating curve I'm going to

show you is the heating curve for water so if we look at the heating curve for water it's going to look something like

that and so what happens below Z ° C well that's going to be a solid it's going to be ice what happens as we go

above it it's going to turn into water and then above 100° Celsius going to turn into vapor but why is the why is it

a flat line here it seems like we're just losing energy in other words we're adding energy the whole way across why

isn't the temperature increasing here well what's happening is as we move add energy to ice as we reach that point

what we have right here is both ice and water so we see a transition from a solid to a liquid and so that energy is

going into that molecular motion of that solid becoming a liquid likewise where is the energy going here it's going into

the energy of those Vapor molecules as they jump off and so as you heat water it's going to increase to to around 100

degrees celsus depending on your elevation but at that point it eventually jumps into a vapor and so we

could look at a heating curve to see the transition between both solid and liquid and then our next video which is going

to be on gases if we flip this thing around then we've got just a cooling curve and then did you learn this that

we can use a particulate model so we use that model that pH model to explain the difference between solid and liquid

remember that big point is when we move to a liquid they show translation they can move around each other and I hope

that was helpful [Music]