in this video, we're going to begin our lesson on concentration, ingredients and diffusion. And so a concentration Grady int is really just defined as a difference in the concentration of a substance between two different areas. And so if we're comparing two different areas and one area has a higher or lower concentration than a different area, then ah, concentration. Grady int exists because there's a difference in the concentration between those two areas. However, if we're comparing the concentration of two areas and there's no difference in the concentration, then no concentration Grady int exists. And so that's why a concentration Grady in is really just a difference in the concentration of a substance between two areas. Now a molecule will be moving with or down its concentration. Grady int. When that molecule is going from an area of high concentration down to an area of low concentration and a molecule, on the other hand, will be moving against or up its concentration. Grady int when that molecule is going from an area of low concentration to an area of high concentration. So let's take a look at this image down below to clear up that idea so notice that this image is all about concentration. Grady INTs and it's broken up into two halves. We got the left hand side over here. We got the right hand side over here, so let's focus on the left hand side first and notice that we have a high concentration of this pink molecule over here on the left hand side. Whereas over here on the right hand side, we have quite a low concentration of these pink molecules. And so if one of these pink molecules is going to move from an area of high concentration towards an area of low concentration on the molecule movement is represented by the biker here thin. This means that the molecule will be moving down or with its concentration, Grady in moving from the area of high concentration down to the area of low concentration. And so, just like it doesn't really take a lot of energy for a biker. Thio basically cruise down a hill. It also does not take any energy for a molecule to move down or with its concentration. Grady int. So here we can indicate that absolutely no energy is required for molecules to move down or with their concentration Grady int from areas of high concentration towards areas of low concentration. Now, over here on the right hand side noticed that we have an image that has an area of low concentration of pink molecules over here on the left hand side and an area of much, much, much higher concentration of the pink molecule over here on the right hand side. And so if a molecule is trying to move from an area of low concentration towards an area of high concentration and the movement of the molecules represented by this biker that is going uphill, this means that the molecule would be moving up or against its concentration. Grady int. And so, um, it will be moving up or against its concentration gradient when it moves from an area of low concentration to an area of high concentration. And so, just like it would take a lot of energy for a biker to bike up Ah hill. It takes energy for a molecule to move up or against its concentration, greedy in from an area of low concentration to an area of high concentration. So notice here we're saying that energy is required and once again, this is an idea that will get to talk even Maura about as we move forward in our course. But for now, this year concludes our introduction to the concentration Grady int, and also molecules moving with or down the concentration, radiant and or against or up the concentration radiant. And so we'll be able to get some practice applying these concepts as we move forward in our course and in our next lesson video, we'll get to talk Maura about diffusion, so I'll see you guys in our next video.