Physical properties

0:00- [Instructor] You have a box of various things with you, some metallic rods. You have some liquids, balloons, coins, and even salt and sugar, and you have a baby brother who doesn't know the names of any of these, let's say. Now your task is to instruct him to get particular things from the box.

0:17How would you do that? Think about it for a while. Well, let's see. If you want your baby brother to get this particular coin, you could use its color. You could say, "Hey, get me that gold coin." If you wanted this one, you would say, "Hey, get me that brown coin."

0:30So over here, you're using color to differentiate between them, right? Okay, what about this one? What if you wanted to instruct your brother to get the rubbing alcohol, for example? How would you differentiate between these two? Well, you can now ask your brother to smell it, right?

0:48The water does not have any smell. The rubbing alcohol has some kind of a medicinal smell, right? So you could say that, "Hey, get me the one that has the medicinal smell." So in this particular case, you're gonna use the scent to differentiate between these two.

1:01Okay, let's take another. This time, you want him to fetch the helium balloon. How will you help him identify that? Well, we know a helium balloon floats. So you could tell your brother, "Hey, get me the balloon that's floating." So what are you using to differentiate this time?

1:16Well, why does a helium balloon float in the air in the first place? Well, it turns out that's because helium is lighter than the air. To be more specific, to be more technical, I should say that helium has less density compared to air. So this time, we're using density to differentiate between these two balloons.

1:36What about these two? Well, they pretty much have the same color. They also have the same length. So how are you gonna tell them apart? Ooh, ooh. You know what? You can bring a magnet close by. And iron is attracted to magnet, but lead does not. So if you wanted him to fetch the iron bar, you could tell your brother, "Hey, go grab a magnet and see which one attaches to the magnet.

1:59That is the one that I want you to bring it to me." So this time, you're making use of the fact that one of them is magnetic, and the other one is not. That's how you're differentiating between them. And finally, finally, how are you gonna help your brother differentiate between these two?

2:14Let's say you want him to bring the sugar. What are you gonna say>? Well, you can just ask him to taste it. I mean, all chemicals should not be tasted, but salt and sugar, well, they're pretty safe. So you just ask your baby brother to taste it and you say, "Hey, the one that is sweet, will you get that for me?"

2:29And so this time, we are using the taste to differentiate between them. Okay, that was fun. But these things that we just use to differentiate between the different stuff, we give a name to that. We call them properties. Okay, so what exactly are properties? Well, properties are the characteristics that help identify a substance.

2:51We used colors and density and taste to identify specific substances, right? But guess what? Properties can be of two kinds. We can have physical properties, and we can have chemical properties. These are all physical properties. "But what is a physical property?" you may ask now, right?

3:10Well, physical properties are the ones that can be observed or measured without changing the identity of the substance. What does that mean? Well, let's go back. Let's go back, and let's look at these examples, okay? If you go back to the color, well, you measured or you observed the color, and when you did that, you didn't change the identity of the substance, right?

3:30Gold coin, that still stayed gold. Copper coin still stayed copper. So measuring or observing did not change the identity. Here's another example. When you were asking your brother to smell them, the act of smelling, which is basically figuring out the scent, that did not change.

3:47Again, the identity of substance, water, did not change. The alcohol did not change. It stays the same. So do you see what I mean? If you look at all these properties, if you try to measure them or observe them, they do not change the identity substance at all.

3:59Such properties are what we call physical properties. I'm sure you may be wondering now, "Wait, are there properties that when you measure or observe, it can change the identity of the substance?" Yes, they can, and we call them chemical properties. And I'm sure you must be wondering, "Well, what are they?"

4:14Well, let's not worry about chemical properties in this video. We'll talk about them in other videos. But again, coming back over here, let's take an example. Here's a piece of iron. Can you think about some of the physical properties over here? All right, let's see.

4:26It has some color. It has some length. That's a physical property. It has some density. That's another property. Then it occupies some space, and it has some volume. It will have some mass, and it's magnetic. So these are some examples of the physical properties.

4:42Finally, there's another way to categorize properties. We can categorize them as intrinsic or intensive properties and extrinsic or extensive properties. Okay, what exactly are these? Well, intrinsic properties or intensive properties are the one that does not depend on the amount of substance, and extrinsic are the ones that does depend on the amount of substance.

5:02But again, what does that mean? Let's take an example. Let's say we have another small piece of iron. Now think about the property magnetic. Both the pieces of iron are magnetic, right? In fact, whether iron is magnetic or not does not depend upon how much iron you have.

5:17So this does not depend upon the amount of substance, and therefore, magnetic is an intensive or intrinsic property. Think about density. Well, again, the density of iron is the same, regardless of how small or how big a iron you have. Iron has a density of over 7.87 grams per cm cubed.

5:33So density also does not depend on the amount of substance. It's intensive. Similarly, think about color. Well, iron is gray, regardless of how much amount of iron you have, and so color is also an intrinsic property. Now, think about volume. Well, volume does depend on the amount of substance that you have, the amount of iron that you have. This has a smaller volume.

5:50This has a bigger volume. So volume does depend on the amount of substance. It's an extrinsic property. Similarly, look, length does depend on the amount of substance. This has bigger length. This has smaller length. Extrinsic. What about the mass? Well, again, this has more mass compared to this one, so mass does depend on the amount of substance.

6:09So that's also extrinsic. So putting it all together, properties help us identify a substance, and there are two kinds. We have physical and chemical. Physical are the ones that can be observed or measured without changing the identity of the substance. And another way to classify properties is we can think of them as intrinsic properties, which does not depend on the amount of substance.

6:30And you can also have extrinsic or extensive properties that does depend on the amount of substance.