Read and listen to the fact sheet again. Answer the questions.

1. What is true about the amount of water on Earth?

2. Why does water vapour condense?

3. What happens to a glass of water on a hot day?

4. Name two forms of precipitation. Do you know any more?

5. What are the three states that water can be in?

                                        THE WATER CYCLE

Now here is a challenge for you. Go and get a glass of water and take a look at it. Can you guess how old it is? Well, your water perhaps fell from a cloud just a couple of weeks ago, but it has been around for the same length of time as planet Earth! That means that your glass of water was around when the first creatures swam in the sea and when the dinosaurs roamed the Earth. But how is this possible?

The fact is that the quantity of water on the Earth remains the same over time and it constantly goes through the water cycle. In the cycle, there is continuous movement of water on, above and below the surface of the Earth. Firstly, the sun heats the water in the rivers, seas and oceans, and it evaporates into the air. Plants and trees lose water, too, and this also goes up into the air. The water vapour then cools and condenses into small drops which form clouds. You can see how condensation happens if you look again at your glass of water on a hot day. After a short time, water from the air condenses onto the cold glass. Back to the sky, though, and the next step is that the clouds gradually get heavier and heavier until they can’t hold the water any more, and it falls to Earth as rain, sleet or snow.

Water can change state from liquid to vapour to solid during the cycle, but any form of water that falls from the clouds is called precipitation. When on Earth, some of the water runs into rivers, lakes and streams and becomes surface water. Some enters the ground and forms underground rivers or lakes before eventually flowing back to the seas and oceans. The cycle is complete.

Fill in the blanks:

Maybe you recycle cans, glass and paper. Do you know that nature recycles, too? One of the things nature (1)............ is water.Water goes from oceans, lakes and river into the air. Water falls from the air as (2)............ or snow. Rain and snow eventually find their way back to the ocean. Nature's recycling program for water is (3)............ the water cycle.

The water cycle has 4 stages: storage, evaporation, precipitation and runoff. Water on the Earth gets stored (4)............ oceans, lakes, rivers, ice and even underground. Water goes from storage into the atmosphere by a process called evaporation. When water evaporates, it changes from a liquid (5)............ a gas, called water vapor. Water vapor goes up into (6)............ atmosphere. Water returns to the Earth as precipitation in rain or snow by changing into drops of water (7)............ the air gets cold enough. Clouds are collections (8)............ water droplets. Most precipitation falls into the oceans and go right back into storage.

Water that falls on land always flows from (9)............ places to lower ones. This flow is called runoff. Water from land flows into streams. Streams join together to make (10)............ and eventually the water flows into storage in the oceans.

Read the following passage, and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions.

What makes it rain? Rain falls from clouds for the same reason anything falls to Earth. The Earth’s gravity pulls it. But every cloud is made of water droplets or ice crystals. Why doesn’t rain or snow fall constantly from all clouds? The droplets or ice crystals in clouds are exceedingly small. The effect of gravity on them is minute. Air currents move and lift droplets so that the net downward displacement is zero, even though the droplets are in constant motion.

Droplets and ice crystals behave somewhat like dust in the air made visible in a shaft of sunlight. To the casual observer, dust seems to act in a totally random fashion moving about chaotically without fixed direction. But in fact dust particles are much larger than water droplets and they finally fall. The cloud droplet of average size is only 1/2500 inch in diameter. It is so small that it would take sixteen hours to fall half a mile in perfectly still air, and it does not fall out of moving air at all. Only when the droplet grows to a diameter of 1/125 inch or larger can it fall from the cloud. The average raindrop contains a million times as much water as a tiny cloud droplet. The growth of a cloud droplet to a size large enough to fall out is the cause of rain and other forms of precipitation. This important growth process is called “coalescence”.

What are water droplets?

A. They are ice crystals. 

B. They are small drops of dew.

C. They are watery fruits. 

D. They are animals living on ice.

Read the following passage, and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions.

What makes it rain? Rain falls from clouds for the same reason anything falls to Earth. The Earth’s gravity pulls it. But every cloud is made of water droplets or ice crystals. Why doesn’t rain or snow fall constantly from all clouds? The droplets or ice crystals in clouds are exceedingly small. The effect of gravity on them is minute. Air currents move and lift droplets so that the net downward displacement is zero, even though the droplets are in constant motion.

Droplets and ice crystals behave somewhat like dust in the air made visible in a shaft of sunlight. To the casual observer, dust seems to act in a totally random fashion moving about chaotically without fixed direction. But in fact dust particles are much larger than water droplets and they finally fall. The cloud droplet of average size is only 1/2500 inch in diameter. It is so small that it would take sixteen hours to fall half a mile in perfectly still air, and it does not fall out of moving air at all. Only when the droplet grows to a diameter of 1/125 inch or larger can it fall from the cloud. The average raindrop contains a million times as much water as a tiny cloud droplet. The growth of a cloud droplet to a size large enough to fall out is the cause of rain and other forms of precipitation. This important growth process is called “coalescence”.

What can be inferred about drops of water larger than 1/125 inch in diameter?

A. They never occur.

B. They are not affected by the force of gravity.

C. In still air they would fall to the ground.

D. In moving air they fall at a speed of thirty-two miles per hour.

Read the following passage, and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions.

What makes it rain? Rain falls from clouds for the same reason anything falls to Earth. The Earth’s gravity pulls it. But every cloud is made of water droplets or ice crystals. Why doesn’t rain or snow fall constantly from all clouds? The droplets or ice crystals in clouds are exceedingly small. The effect of gravity on them is minute. Air currents move and lift droplets so that the net downward displacement is zero, even though the droplets are in constant motion.

Droplets and ice crystals behave somewhat like dust in the air made visible in a shaft of sunlight. To the casual observer, dust seems to act in a totally random fashion moving about chaotically without fixed direction. But in fact dust particles are much larger than water droplets and they finally fall. The cloud droplet of average size is only 1/2500 inch in diameter. It is so small that it would take sixteen hours to fall half a mile in perfectly still air, and it does not fall out of moving air at all. Only when the droplet grows to a diameter of 1/125 inch or larger can it fall from the cloud. The average raindrop contains a million times as much water as a tiny cloud droplet. The growth of a cloud droplet to a size large enough to fall out is the cause of rain and other forms of precipitation. This important growth process is called “coalescence”.

What is the diameter of the average cloud droplet?

A. 1/16 inch 

B. 1/125 inch

C. 1/2500 inch 

D. one millionth of an inch

Read the following passage, and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions.

What makes it rain? Rain falls from clouds for the same reason anything falls to Earth. The Earth’s gravity pulls it. But every cloud is made of water droplets or ice crystals. Why doesn’t rain or snow fall constantly from all clouds? The droplets or ice crystals in clouds are exceedingly small. The effect of gravity on them is minute. Air currents move and lift droplets so that the net downward displacement is zero, even though the droplets are in constant motion.

Droplets and ice crystals behave somewhat like dust in the air made visible in a shaft of sunlight. To the casual observer, dust seems to act in a totally random fashion moving about chaotically without fixed direction. But in fact dust particles are much larger than water droplets and they finally fall. The cloud droplet of average size is only 1/2500 inch in diameter. It is so small that it would take sixteen hours to fall half a mile in perfectly still air, and it does not fall out of moving air at all. Only when the droplet grows to a diameter of 1/125 inch or larger can it fall from the cloud. The average raindrop contains a million times as much water as a tiny cloud droplet. The growth of a cloud droplet to a size large enough to fall out is the cause of rain and other forms of precipitation. This important growth process is called “coalescence”.

What is the main topic of the passage?

A. The mechanics of rain. 

B. The climate of North America.

C. How gravity affects agriculture. 

D. Types of clouds.

Read the following passage, and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions.

What makes it rain? Rain falls from clouds for the same reason anything falls to Earth. The Earth’s gravity pulls it. But every cloud is made of water droplets or ice crystals. Why doesn’t rain or snow fall constantly from all clouds? The droplets or ice crystals in clouds are exceedingly small. The effect of gravity on them is minute. Air currents move and lift droplets so that the net downward displacement is zero, even though the droplets are in constant motion.

Droplets and ice crystals behave somewhat like dust in the air made visible in a shaft of sunlight. To the casual observer, dust seems to act in a totally random fashion moving about chaotically without fixed direction. But in fact dust particles are much larger than water droplets and they finally fall. The cloud droplet of average size is only 1/2500 inch in diameter. It is so small that it would take sixteen hours to fall half a mile in perfectly still air, and it does not fall out of moving air at all. Only when the droplet grows to a diameter of 1/125 inch or larger can it fall from the cloud. The average raindrop contains a million times as much water as a tiny cloud droplet. The growth of a cloud droplet to a size large enough to fall out is the cause of rain and other forms of precipitation. This important growth process is called “coalescence”.

What is an example of precipitation?

A. rain 

B. lightening 

C. wind 

D. thunder

Read the following passage, and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions.

What makes it rain? Rain falls from clouds for the same reason anything falls to Earth. The Earth’s gravity pulls it. But every cloud is made of water droplets or ice crystals. Why doesn’t rain or snow fall constantly from all clouds? The droplets or ice crystals in clouds are exceedingly small. The effect of gravity on them is minute. Air currents move and lift droplets so that the net downward displacement is zero, even though the droplets are in constant motion.

Droplets and ice crystals behave somewhat like dust in the air made visible in a shaft of sunlight. To the casual observer, dust seems to act in a totally random fashion moving about chaotically without fixed direction. But in fact dust particles are much larger than water droplets and they finally fall. The cloud droplet of average size is only 1/2500 inch in diameter. It is so small that it would take sixteen hours to fall half a mile in perfectly still air, and it does not fall out of moving air at all. Only when the droplet grows to a diameter of 1/125 inch or larger can it fall from the cloud. The average raindrop contains a million times as much water as a tiny cloud droplet. The growth of a cloud droplet to a size large enough to fall out is the cause of rain and other forms of precipitation. This important growth process is called “coalescence”.

What does “in constant motion” in paragraph 1 mean?

A. moving all the time 

B. always having feeling

C. never changing 

D. falling down easily

Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions

       Archimedes’s Principle is a law of physics that states that when an object is totally or partially immersed in a fluid, it experiences an upthrust equal to the weight of the fluid displaced. The principle is most frequently applied to the behaviour of objects in water, and helps to explain floating and sinking, and why objects seem lighter in water. It also applies to balloons.

        The key word in the principle is “upthrust”, which refers to the force acting upward to reduce the apparent weight of the object when it is under water. If, for example, a metal block with a volume of 100 cm³  is dipped in water, it displaces an equal volume of water, which has a weight of approximately 1 N (3.5 oz). The block therefore seems to weigh about 1 N less.

        An object will float if its average density is less than that of water. If it is totally submerged, the weight of the water it displaces (and hence the upthrust on it) is greater than its own weight, and it is forced upward and out of water, until the weight if water displaced by submerged part is exactly equal to the weight of the floating object. Thus a block of wood with a density six tenths that of water will float with six tenths of its volume under water, since at that point the weight of fluid displaced is the same as the blocks’s own weight. If a dense material is made into a suitable shape, it will float because of Archimedes’s principle. A ship floats, whereas a block of iron of the same mass sinks.

        It is also because of Archimedes’s principle that ships float lower in the water when they are heavily loaded (more water must be displaced to give the necessary upthrust). In addition, they cannot be so heavily loaded if they are to sail in fresh water as they can if they are to sail in the sea, since fresh water is less dense than sea water, and so more water must be displaced to give the necessary upthrust. This means the ship is lower in the water, which can be dangerous in rough weather.

         From “Archimedes’s Principle”, MicrosoftÒ Student 2008[DVD]. Microsoft Corporation, 2007.

What happens when something is immersed in a fluid?

A. It will be pushed further down with a force, equal to the weight of the fluid displaced.

B. It receives an upward force, equal to the weight of the fluid displaced

C. It receives a download force, equal to the weight of the fluid displaced

D. The fluid will expand the object and overflow to the floor