 Many changes keep happening around us. Some changes happen automatically by themselves and some are done by human activities. So for example, plants grow leaves change color and they dry up and fall from trees. Flowers bloom and they can also wither. Fruits can ripen and fall from trees. Even seasons change, such as winter, summer and rain. All of these changes they occur automatically. But there are some changes like lighting up a firework or lighting up let's say a diya. Or changing milk to paneer or cottage cheese. These changes are carried out by humans. But there is one thing common in all of these examples. There is a change either in the color, shape, smell and in some changes like meditating of ice there is even a change of state of some objects. So we can say that any change in the state, shape, color, taste or smell of an object is called a change. And in this video we will look at one type of change. So let's look into that. Let's say we have milk to begin with and we're in the process of making curd. So we have two ways to do that. We can either add some curd or we can add lemon. In the first case the change to curd by adding some curd happens slowly. It takes some time. And in the second case when you add some lemon juice to milk, the milk curdles quickly. So when a change takes long time to complete it is said to be slow. And when a change happens quickly it is said to be a quick change. Quick changes take less time to complete. They happen at a faster rate. Let's look at some more examples of these type of changes. Okay. I'm going to show you some changes. And I want you to take some time and try and categorize which change could be a slow change and which change could be fast. So there you go. The first one is burning a matchstick. The second is popping up an inflated balloon. The third is growth of nails. And the fourth is resting of iron. Take five seconds and categorize these four changes under slow and fast or quick. All right. So the first two, they happen rather quickly, right? A matchstick can immediately ignite. A balloon can immediately pop when pricked with a sharp object. But it takes time for human nails to grow and it takes a lot of time for an object to rust. So these two are slow changes and these two are fast or quick changes. All right. Here I have some more examples. So the first is you can imagine this is an image of, this is a sunset, but you can think of a change of sun rising up and then setting at the end of the day. The second is melting of ice. This is drying of clothes on a hot summer day. And these are fireworks. Again, think about which of these changes could be slow or fast. Okay. So the first one, at least when you compare it to the other changes that are happening, the first one takes a lot of time because it takes around 12 hours between sunrise and sunset. The rate at which ice is melting really depends how low or higher the temperature is. In higher temperatures, ice melts really quickly. It's a fast change. But if the temperature is really low, it will take a lot of time for ice to melt. And then drying up of clothes. This is also not a very quick process because it takes some time for the clothes to dry up. Fireworks, this is a very fast process. Immediately when you ignite a firework, it goes off and bursts. Okay. So some changes can be categorized as slow. Some can be categorized as fast. But there is no hard and fast tool if a process is slow or fast. You can only measure the slowness and how fast a change is related to something else. So you can only say that change A is slow or fast when you compare it with some other change.