You know that balloons must be kept away from sharp objects. They also needed to be kept away from flames. A fire can weaken the rubber and cause it to break. However, in this experiment you will find out how you can hold a balloon directly in a flame without breaking the balloon.

    Materials needed:

● two round balloons not inflated(充气的)

● several matches

● water

    Inflate one of the balloons and tie it. Place 1/4 cup of water in the other balloon, and then inflate it and tie it. Light a match and hold it under the first balloon. Allow the flame to touch the balloon. What happens? The balloon breaks, perhaps even before the flame touches it. Light another match. Hold it directly under the water in the second balloon. Allow the flame to touch the balloon. What happens to this balloon? It doesn't break.

    Why does the balloon with no water break in the flame? The flame heats the rubber of both balloons. The rubber of the balloon without water becomes so hot that it becomes too weak to resist the pressure of the air inside the balloon. However, when the balloon with water in it is placed in the flame, the water takes in most of the heat from the flame. Then, the rubber of the balloon doesn't become very hot, it doesn't weaken, and the balloon doesn't break.

    Water is a particularly good absorber(吸收者) of heat. It takes a lot of heat to change the temperature of water. On the other hand, when water cools, it gives off a great deal of heat. That's why areas near oceans or other large bodies of water don't get as cold in winter as areas at the same latitude(纬度) further inland.

    Some materials are obtained from natural resources that are changed by chemical processes in a laboratory. The resulting artificial materials are synthetic, or human-made.

    Plastic is a synthetic substance, obtained from petroleum, a fossil fuel. The molecules（分子）in petroleum are split and then linked into chains. Plastic is an example of a polymer, a material made of repeating patterns of atoms linked together. Most polymers are synthetic. They are made by polymerization, the process of chemically linking many smaller molecules to form a larger molecule that has different physical features. Some polymers, such as proteins, occur naturally.

    Plastic is a key component of many products. When heated into an almost-liquid form, plastic can be made into fibers, sheets, or molds（模具）. It can be mixed with other elements to remain flexible, or it can harden into a solid. Plastic fibers can be made into clothing or carpeting. Sheets of plastic can be made into plates. Molded plastic can be sued for protective helmets or car bumpers.

    Most plastics can be reheated and remolded repeatedly. This feature makes plastic very easy to use. Polymers can be pulled into fine strings or molded into almost any kind of shape. For example, tubes of plastic can be shaped into bottles by different processes. One such process is extrusion blow-molding. Most plastics are also resistant to many chemicals that might harm other materials. This quality is the reason that so many cleaning liquids are packaged in plastic bottles.

    Plastics are good insulators that can stop electricity or heat to pass through. Look around your kitchen, and observe where plastics are used. Pot handles are sometimes made of plastic, as are cooking tools, toaster controls, and microwave cookware. Food-storage wraps and containers may be made of plastic. Take a walk outdoors, and note all the plastic items you see. Gardening tools, such as watering cans and sprayers, are often made of plastic. Swings and slides made of plastic do not become as hot as metal, so they are safer for play. Because plastics can be heated, remolded, and made into something else, they can be recycled and reused.

    For over 70 years, UNICEF has been putting children first, working to protect their rights and provide the assistance and services they need to survive and develop all over the world.

    It's the end-of-year giving season, and UNICEF has lots of good news to share about the influence its supporters have had on the lives of children. Thanks to its generous donors, UNICEF has helped save more lives than any other humanitarian organization.

    Monthly donors are a major reason why UNICEF can make that claim, according to Karla Coello, UNICEF USA Senior Director for Monthly Giving. “Last year, UNICEF responded to 377 humanitarian emergencies, from conflicts to natural disasters,” says Coello. “Emergency appeals bring in important revenue - but after the emergency, there are still a lot of things children need to make life bearable. That's what our monthly donors provide.”

    When drought destroys crops, conflict forces families from their homes, an epidemic breaks out or a disaster strikes, children suffer most. And in some countries, even the best of times are dangerous for its youngest citizens. Every day more than 15,000 children under 5 die from preventable causes.

    Protecting children before, during and after a crisis requires a reliable source of funding. The constant stream of revenue provided by monthly donations enables UNICEF to reach children with what they need most when they need it, prepositioning emergency supplies before a disaster strikes and continuing to build sustainable solutions after an immediate crisis has subsided.

    Monthly giving is also important to funding large-scale interventions(介入). Thanks to UNICEF's global immune campaigns, the world is now nearly free of polio(小儿麻痹症)and there are only 14 countries where mothers and children still face maternal and neonatal tetanus(破伤风)deadly threat. And UNICEF programs in 120 countries are helping to prevent and treat malnutrition, which is linked to nearly half of all deaths of children under 5.

    “UNICEF USA monthly donors are our most engaged, most dedicated supporters,” says Rebecca Volpe, UNICEF USA Manager, Monthly Giving. “So we do our best to make them feel appreciated by keeping them thoroughly updated about the powerful impact they are having and showing them how much they matter to us.” In turn, monthly donors tend to be dedicated supporters. “Protecting children - giving them opportunities to play, learn, feel safer, heal - is critical to us,” explained a survey respondent, expressing a commitment to children that UNICEF USA's Monthly Giving team sees every day.

    Supporters who sign up with UNICEF USA to give monthly automatically become members of the Guardian Circle, which affords them benefits, including:

    Annual statements to make tax time easier

    An easy-to-use donor access that simplifies modifying gift amounts, updating payment methods and making other changes, including the timing of donations with the option to cancel at any point

    Targeted communications in the form of monthly statements and a quarterly 8-page newsletter with stories from the field.

    A team available to answer questions via email or phone.

    “We have some donors who are on fixed income, others who can afford to make considerable monthly donations," says Coello. “Whether you give $5 or $700 a month, you are super important to us. What's important is that they all really want to give and help children. And that's amazing.”

    It can be time-consuming and difficult to track charitable donations. At end of year, Guardian Circle monthly supporters receive one statement that makes filing tax returns easier - and it's always delightful to see how much good has been done for the world's most vulnerable(受伤害的)children.

    Have you ever been to a music festival? Well if you live in the UK, the answer is probably yes. The number of festivals has grown greatly over the last few years and now there are around 200 every summer. So let's look at the history of four famous festivals.

    The Glastonbury Festival is a five-day festival of contemporary (当代的) performing arts held most years in Somerset, in the south-west of England. There are a rock and pop stage, a jazz stage, the Avalon stage, a theatre comedy stage, a cinema tent, a dance tent and a circus (马戏团). The festival started in1970and about 120, 000 people go to it every summer.

    The Reading Festival is truly world-class with rock and pop bands (乐队) appearing from all over the world, particularly (尤其) the USA. About 80, 000 music fans go to Reading every August Bank Holiday. The festival first came to its present site on the banks of the River Thames in Reading in 1971, when it moved from Plumpton in Sussex. It is still on the same site over 47 years later!

    WOMAD stands for World of Music, Arts and Dance and was the idea of rock musician Peter Gabriel to promote (宣传) world music. The WOMAD Festival started in 1982 and takes place in July at Charlton Park, near Malmesbury in Wiltshire, and you can see different bands and musicians from all over the world. The festival welcomes over 26, 000 visitors each year.

    The one-day Monsters of Rock Festival at the National Bowl in Milton Keynes was first held in 1980 and gave visitors the chance to hear the very best of hard rock and heavy metal. There were no festivals between 1996 and 2003 as a result of changing musical fashions, but now it has returned and grown into a two-day festival with a campsite for the 30, 000 people who go there in summer days.

Have you ever heard of invisible ink? You may have seen it in movies. When light is shone on the paper which invisible ink is written on, you can read it!

As magical as this seems, the change in color is due to science. The ink is absorbing higher energy light and giving lower energy light. This reaction is an example of fluorescence (荧光) .

Light is a very broad term that describes a range of electromagnetic rays, including gamma rays, infrared light (红外光) and ultraviolet light. One part of the electromagnetic visible light is the colors that we can see with the human eye. These rays travel in curvy lines and each type of the ray is characterized by a different wave pattern. For example, Gamma rays have a shorter wavelength than infrared light. Shorter wavelength is connected with higher energy, so gamma rays also have more energy than infrared light.

Corals (珊瑚) are animals that live underwater. And the corals in the Red Sea exhibit fluorescence. Why is this happening? Scientists have shown that fluorescent objects absorb higher energy light and release lower energy light. Since the corals of the Red Sea are deep in the water where there is very little visible light, scientists theorize that these corals absorb ultraviolet light and produce visible light. They have special photo proteins, which enable them to change invisible light to visible light.

Fluorescence is not just used to create pretty colors. Corals have developed photo proteins for a biological reason. The visible light is used by algae (海藻) , which are eaten by the coral, to make food through photosynthesis (光合作用). The visual character of these photo proteins could also be used for biomedical research. They can highlight cells and cell structures under a microscope.

Isn't it amazing that a simple organism that we don't think very much of is not only grand but could also have so many potential uses in medical research!