Eugenie Foo

HELLOHELLO! :D
Today we had a long lesson full of information! So everybody, here it goes!

We did alot of things today and it includes the cloud-making experiment and learning the different types of rain. Firstly, the coke bottles! Before we started on the experiment, Mr Heah revised water cycle, also known as the hydrological cycle, and he revealed that we would be "making clouds" inside the coke bottles. Mr Heah gathered us around the teacher's table and he demostrated "making clouds". I'm sure everyone was amazed, and so was I! It was cool, to see clouds appear and disappear before our eyes. For the experiment, we needed a 1.5 litre coke bottle, and a little bit of water in the bottle. All we had to do was to extinguish a matchstick, trap the smoke from the matchstick in the bottle and cap the bottle up. Then, we had to squeeze the bottle and release it continuously. While squeezing and releasing the bottle, we see a phenomonen! x) We notice that when squeezing the bottle, the bottle is clear inside. However, when releasing the bottle, the inside of the bottle turns cloudy! Seeing this, we have just "made clouds"!

After the experiment, Mr Heah wrote two questions on the board,
1. Why is there a need to squeeze the bottle?
2. Why is the smoke needed?

1. Firstly, how do clouds form? Water vapour must become water droplets in order to form clouds. When we squeeze the bottle, the volume of the bottle becomes smaller, and there is a higher pressure in the bottle, and the temperature is high, and water remains as water vapour. When we release the bottle, the volume of the bottle becomes larger, and the pressure becomes lower, the temperature is low, and water droplets form! Therefore we squeeze the bottle to allow the pressure to change and cause water droplets to form as described above.

2. Now why is the smoke needed? Water droplets are really really small and therefore they only collide and bounce off. To make water droplets coalesce into a visible cloud, there is a need for a surface. And in the case of the experiment, aerosols (eg. smoke) serve as a condensation nuclei, which allow water droplets to coalesce into a cloud, therefore smoke is needed.

(:
Now, the different types of rain! There's 3 types, namely the relief rain, the frontal rain, and convectional rain. We were separated into 6 groups and were given 5 minutes to explain the various types of rain. This is what we learnt about the 3 types of rain:

1. Relief rain.
As the name suggests, this got to do with the relief of a mountain. As moisture-laden air approaches the mountain ranges, the relief of the mountain forces air to rise, and adiabatic cooling (air forced to rise, expand and condense, and water droplets form) occurs, and clouds form, and eventually, rain falls. The unique thing about relief rain is that all rain would only fall on the leeward side of the mountain. Why? At the windward side of the mountain, there is less moisture, and air sinks. As the air gets warmer, condensation no longer occur, and no clouds would be form, thus no rain.

2. Frontal rain.
As warm air meet cold air OR as cold air meet warm air, they do not mix. Instead, the denser cold air would force warm air to rise, and adiabatic cooling occurs, and clouds form, and eventually, rain falls. The unique thing about frontal rain is that this type of rain can only be found at temperate regions.

3. Convectional rain.
Heat from the sun heats up the ground and ocean, causes the air to get warmer (lower density) and rise, adiabatic cooling occurs, and clouds form, and eventually, rain falls. The unique thing about convectional rain is that it only happens at tropics and equatorial regions, and it would only occur in the day time, from afternoon to evening.

Yay, that marks the end of the lesson! It was an enriching lesson, and I never knew there was different types of rain! I have learnt how to "make clouds". I have also learnt what happens before it rains, and most importantly, I have learnt to use the correct terms in replacement of the layman terms, such as adiabatic cooling, coalesce, aerosols! Till next time, haha. :D

Comments: (here, name at bottom)
The most important thing to take note is the process how the air is forced to rise up. And the thing following it is just adiabetic cooling, clouds form and rain. The names of the types of rain also suggest what forces the air to rise. RELIEF of the mountain, hot air rises at its FRONT(AL) with cool air, and hot air rises up simply because of CONVECTIONAL air flow <- Shorter and easier to memorise. ( by Minh ).