How something happens/works

How Rain Happens

As the sun heated up the water in the cup, some of the water evaporated into a gas called water vapor. You can’t see water vapor, but you can see what happened next. The water vapor turned back into a liquid, and little drop of water formed on the inside of the bag—this is called condensation. When several droplets of water stuck together, they became heavy enough to pull each other down the sides of the bag. If you left this project taped to your window for long enough, all of the water from inside the cup should eventually end up in the bottom of the bag!

This is exactly how clouds form and make rain. Water from rivers, lakes, streams, or oceans evaporates into the air when it is heated up by the sun. As the water vapor rises up in the air, it condenses, or starts to cool down and turns back into a liquid. Then, droplets of water start to stick together as clouds. When enough droplets stick together in the clouds, they become large and heavy and are pulled down towards the earth by the force of gravity. When water drops fall from clouds, it is called rain. Sometimes the droplets freeze before they get to the ground and become hail, sleet, or snow!

Questions:

1. What does the text talk about?
2. When does evaporation happen?
3. Why can't you see its process?
4. Why is this process called the cycle of water?

How We Breathe

The nose, trachea and lungs are the main organs which make up the respiratory system. This system allows the exchange of gases which are needed for us to live. Breathing happens when the brain sends a message through the nerves to the intercostal muscles which lie between the ribs and diaphragm. When the instruction is received, the muscles pull the ribs outwards and the diaphragm relaxes so that the space in the chest gets bigger. Because the pressure in the chest gets lower, air rushes in to fill the lungs. This air is first taken in through the nose or mouth. It then travels into the throat (the pharynx) and on through the voice box (the larynx). The opening to the voice box has a cover over it called the epiglottis. This cover opens when a breath is taken. In this way, the air is able to flow down the trachea but food is kept out. After passing down the trachea the air travels into the lung down either the right or left bronchus, through the bronchioles and at last into tiny air sacs called alveoli. These are covered with small blood vessels called capillaries. From here, oxygen is finally taken into the blood stream and carbon dioxide is passed back to the lungs. The intercostal muscles then push the rib cage back inwards. As a result, the space in the chest gets smaller and the pressure rises, thus pushing the carbon dioxide back out of the lungs. And it all happens in the space of a single breath!

Questions:

1. Explain each organ and its function in the respiratory system based on the text!
2. Write down all the words in bold and italic and find their meanings and parts of speech!