 In today's video, what we want to go over are the properties of a gas, and in order to go over these properties that a gas has differing from that of a liquid or a solid, let's talk about what a solid, a liquid, a gas looks like at the molecular level first. Whenever we're talking about a solid, we're talking about particles that are very close together. So these solid particles are very close together because of the attractive forces that bind the particles. On the other hand, a liquid, a liquid the particles are, they have more space between them, however they are still somewhat close together. The fact that that space there is in between the particles is what allows a liquid to have a fluid motion. Now we come to a gas. A gas looks much different than that of a liquid or solid where the particles are much more spread out. So one of the main properties of a gas is the fact that the particles that make up that gas are very, have lots of distance between them. Now let's look at some other properties of a gas that differ from that of a liquid or a solid. First of all, they move randomly with high velocity. These gas particles that are out in the atmosphere at room temperature, they move somewhere around a thousand miles per hour. So they have very high velocities and they're moving at random directions. They are very, they have very small attractive forces between the particles. So the particles of a gas don't have very many attractive forces between multiple particles as a solid and a liquid do. Another property is that the volume that actually make up the gas particles is extremely small compared to the volume that that gas occupies. And once again this goes back, goes back to the point that there is so much space in between the particles. The volume that these particles actually make up is extremely tiny compared to the volume that that gas occupies. And also, gas particles are moving at a constant motion in straight paths. And that is until they collide with another gas particle or with the surface of the container that they're contained in. So let's look at, next of all, some properties that we use as scientists to describe gases. The first one is the pressure of a gas. The pressure is defined as the force exerted by gas particles against the wall of its container. So if we have a cylinder filled with gas particles with a pressure gauge, that pressure is simply a measurement of the amount that those gas particles are colliding with the surface of the container that they're in. That is really the definition of a pressure, the pressure of a gas, is how much force and how many collisions are actually occurring when these particles collide with the surface of the container that they're in. Now when we're talking about pressure, let's also go over some of the units that we use to measure pressure. One unit that you'll come across is an atmosphere. You'll also see MMHG, which is millimeters of mercury. Now what is the difference between an atmosphere and millimeters of mercury? One atmosphere is equal to 760 millimeters of mercury. In case you ever have to convert from one unit to another unit in terms of pressure, you will use this equality if converting between atmospheres and millimeters of mercury. Another unit for pressure that you may be familiar with, especially if you work in a hospital, is the torr. Turns out that one atmosphere is also equal to 760 torr. And then finally, the other unit for pressure that you may come into contact with is KPA or kilopascals. And when talking about kilopascals, one atmosphere is equal to 101 kilopascals. Now one of the other properties that we use to describe gases is volume. Volume is simply the space occupied by the gas, alright? So it's the total amount of space that that gas takes up. And what type of units do we use to measure volume? Sometimes you will see the volume of a gas measured in milliliters and other times you will see it measured in liters. The third property that we use to describe gases is temperature. And the temperature is the factor that determines the kinetic energy and rate of motion of gas particles. So the temperature of the gas is relative to the amount or the speed velocity of these gas particles. So as we raise the temperature of a gas, we are increasing the speed or the velocity of these gas particles. And if we increase the velocity of the gas particles, we would expect them to hit the surface of their container with more force and in turn pressure would increase. Now what are some units that we measure temperature of gases in? Well you will see them measured in degrees Celsius or Kelvin. However you must remember any time you are using the temperature of a gas in any type of calculation, it must be converted to Kelvin first. In order to convert a Celsius temperature value to Kelvin, you must add 273. And that will give you the temperature value in Cullen. And then finally the fourth property that we use to describe a gas is simply amount. And you will see this denoted by a lower case in. The quantity of gas present. Make sense? Finally, what are the units that we use to measure amount of gas? Some cases you will see the amount of gas measured in grams. Other cases it will be measured in moles. Now just like temperature, the temperature of a gas must be measured in Kelvin in order to use it in calculations. The amount of gas must be in moles. So if you are given grams and you are asked to calculate some value with the grams of a gas, you must first convert those grams to moles before you can use that variable in your calculation. So hopefully this helped with describing the properties that gases have. Just remember these four points here about a gas and how they differ from that of a solid or liquid.