In most parts of the world, many students help their schools make less pollution. They join “environment clubs”. In an environment club, people work together to make our environment clean.

    Here are some things students often do.

    ◆No—garbage (垃圾) lunches. How much do you throw away after lunch? Environment clubs ask students to bring their lunches in bags that can be used (被使用) again.

    ◆No—car day. On a no-car day, nobody comes to school in a car—not the students and not the teachers! Cars give pollution to our air, so remember: Walk, jump, cycle or run.

    Use your legs! It's lots of fun!

    ◆Turn off the water! Did you know that some toilets can waste (浪费) twenty to forty tons of water an hour? In a year, that would fill a small fiver! In environment clubs, students mend those broken toilets.

    We love our environment. Let's work together to make it clean.  

      Look up in the sky. Do you see any clouds? What do they look like ?Some clouds are fluffy（绒毛状的）and white, like cotton balls. Others are dark, almost black, and make you hold an umbrella. At sunrise and sunset, clouds can look red, purple, or yellow，as if they were colored with crayons. But what are clouds anyway?

   You can't reach out and touch the clouds, but you can make your own in a bottle.

   You need :

   An adult helper

   A huge, empty glass container（容器）

   A metal strainer（滤网）

   Hot water

   Ice

   Do these:

   Step1. Have your helper fill the container with hot water ,leave it there for two minutes, then pour out most of the water, leaving just an inch or two at the bottom of the container.

   Step2. It's your turn now. Put the strainer over the mouth of the container. Fill the strainer with ice. Watch the container.

What happened?

A cloud formed in the container! Some of the hot water at the bottom of the container turned into the hot water vapor. The water vapor rose and met with cold air coming off the ice. When the water vapor condensed（凝结）,it formed a cloud. Hot air rises ad carries with it lots of water vapor. The higher the air rises, the more it cools down. Soon the cold air can't hold all the water vapor so it starts turning into tiny water drops, and becomes a cloud.

     We often read the Air Quality Index （空气质量指标） or AQI reported in the newspaper. The AQI helps us understand what the air quality around us means to our health. The AQI uses colors, numbers and words to tell us about the air. Let's see what these colors and numbers mean.

D

    When a computer works on a group of programs, it can get very hot. Cooling the computer can cost a lot. So some scientists wonder what would happen if the heat from the computer could be used.

    Large Internet companies (公司）such as Google and Microsoft have thousands of computers. As these computers deal with information, they produce lots of heat, so they need huge cooling systems(系统）. These systems send the heat into the air.

    A company in Holland(荷兰） thinks paying to make the computers work and then paying again to cool them are a waste of energy. So the company developed a special device—the e-Radiator.

    Boaz Leupe, head of the company, says the e-Radiator works as a heating system and saves money. He explains that the energy is used twice—once to heat the home and once to cool the computer and that the users don't have to pay to cool their computers.

    Five homeowners in Holland are testing the heating system in their homes.

    "We pay for the computer using, so, in that way, homeowners get heating for free," Boaz says.

    Jan Visser is one of the homeowners. "If you use the computer more, the e-Radiator produces more heat," he says. "It can't provide enough heat if you don't use your computer often." But he is ready to try it. It's a great help for his family.

    The company says e-Radiators produce heat temperatures of up to 55℃. It says the system could save its users about $440 a year.