We're surrounded by chemistry in everyday life. Sometimes it is easy to see, like when your science teacher conducts a big experiment in class. At other times, it can be extremely hard to see everyday chemistry at work, but nearly everything you touch or use has some element of chemistry in it.

    Something as simple as toothpaste contains at least three chemicals, if not more. It is the mixture of them and its chemical reaction that keeps your teeth clean. Other things you use every day are created by chemistry, such as hair products, shampoo and soap. Adding detergent (洗涤剂) to water involves chemistry. Without chemistry, we would never have realized that we need soap to get the oil out of clothes or skin.

    Chemistry not only helps us make products for use, but it also helps us understand the world around us. Chemistry helps us understand what the ozone layer (臭氧层) is and how it protects us. Chemistry also gives us sunscreen to protect us from the sun. Thanks to chemistry, we know bleach (漂白剂) can't be mixed with vinegar, because it can produce poisonous gas. Without chemistry, we wouldn't have had fireworks displays on important days like the Spring Festival.

    Chemistry plays a big role in food preparation. Cooking food causes it to go through a chemical change. That is why cooked food often tastes different from raw (生的) food. Baking is a great example of chemistry. Too much or too little of any ingredient makes a difference to the result of baking, for example, the dough (面团) won't rise or the cake will be flat.

    Chemistry isn't something that just lives in a lab; it's something that you come across hundreds of times every day. If you know how chemistry works, you will get a greater comprehension of the science behind some of the simplest looking things.

    Finding a winter job is often a proof that you're growing up, and it's also a method for earning money to pay for what you dream of. It's never too early to start considering the future. Now, here are some good choices for you!

Retail (零售) Sales

    Retail offers plenty of opportunities for teens that are looking for a job. This type of work can pay from $10 to $15 an hour depending upon the duty you are expected to take on. It can also be great for teens who are friendly and enjoy talking to other people. For more information, call us at 4005075.

Food Service

    A job in the food service industry is a natural fit for sociable teens who enjoy communicating with the public. It allows employees to work as part of a team while learning about following instructions. It also comes with the opportunity to earn between $8 and $10 per hour. Just dial 4005077 for more information.

Babysitting

    This job requires someone who is highly responsible. Though it pays generally between $6 and $8 hourly, it also requires a lot of patience. This is a great choice for teens who wish to make a career in teaching, child care, social work or any other field that makes use of social skills or requires interaction with kids. Got a question? Just dial 4005076.

Housekeeping

    This type of work can bring in about $5 an hour and it will allow teens to learn the tourism industry, so hotels are often looking for more housekeeping staff, and parks often need more people to assist with keeping public areas clean and organized as well. Telephone: 4005079

    If you're a cycling lover, you will have to pay a lot of attention to your bicycle and maintain it well, for bicycle parts are exposed to wear and tear (磨损) over time and you have to examine the bicycle to see if there are any signs of wearing such as scratches, dents (凹陷) etc. Sometimes, a part may not work because it has exceeded its life expectancy. Sometimes, you will need to find replacement parts for it to keep up the performance of the bicycle.

    Different parts of a bicycle will wear at different rates so it is very important that you have a basic understanding about the role played by each part. One of the most important parts of the bicycle is the frame. You will need to choose a frame that lasts for a very long time. Of course, you will see some paint scratches after some time. When you're selecting a frame, you have to think about the material. Aluminium (铝) frames will not rust easily, but they have a higher chance to dent. Steel frames will be hard to dent, but you will need to make sure they get a good paint job so that they won't rust.

    Wheels also experience a lot of wear and tear and you should go for a professional seller when you want to buy wheels. There are different types of wheels that you can buy, like Zipp wheels that provide more aerodynamic efficiency (空气动力学效能). Investing in new tyres instead of going for used is a good idea because you will be able to get more use out of it. The same goes for chain as there's a higher chance of a used chain breaking. You may also experience shifting problems. However, some parts of bicycles such as pedals can be used for a long time and you can find different styles.

    Other parts that you can buy used are seats, handlebars and the stem. When you are buying handlebars, you have to see if there are any dents or if they have been bent out of shape. There shouldn't be any cracks in the seat post or the handlebars. There are many shops where you can buy parts, so you will have to check the references to see how customers respond to them before you buy anything.

    The Top 4 Restaurants of 2018

    No. 4

    Kuya Ja's Lechon Belly (4 stars): 5268-H Nicholson Lane, Rockville, Md. 240-669-4383. kuyajas. com.

    Open: Breakfast, lunch and dinner Wednesday through Monday; breakfast and lunch Tuesdays.

    Prices: Sandwiches, bowls and combination meals, $ 6.99-$ 12.59.

    Sound check: 74 decibels（分贝）/ Must speak with raised voice.

    No. 3

    Little Havana（41/2 stars): 3704 14th St. NW. 202-758-2127. littlehavanadc.com.

    Open: Dinner daily.

    Prices: Sandwiches and mains $ 9-$ 25.

    Sound check: 70 decibels / Conversation is easy.

    No. 2

    Three Blacksmiths (41/2 stars): 20 Main St., Sperryville, Va. 540-987-5105. Three black smiths.com.

    Open: Dinner Thursday—Saturday.

    Prices: Small plates $ 5 - $ 20, large plates and family-style plates $ 24 - $ 94.

    Sound check: 81 decibels / Extremely loud.

    No. 1

    Momofuku（5 stars): 1090 I St. NW. 202-602-1832. ccdc.momofuku.com.

    Open: Lunch Monday through Friday, dinner daily, breakfast Saturday and Sunday.

    Prices: Small plates $ 5 - $15.

    Sound check: 75 decibels / Must speak with raised voice.

    Some years ago, Michel-Andre found himself staring at the body of a dead whale on a beach in the Canary Islands. It was obvious that the animal had been struck violently by a ship——but why? Only later, after surveying the whales which lived in the area and measuring the increase of sound pollution from ships did it become clear that there was a link.

    The whales had become desensitised to the noise of approaching boats and were being struck by them, often seriously. "We never thought that this could be something that could kill," recalls (回忆) Andre, who is the director of the Laboratory of Applied Bioacoustics at the Technical University of Catalonia, Barcelona.

    Andre has spent 20 years developing an advanced system to better understand why incidents like this happen. His underwater microphones have exposed a world of deafening sound and animal communication never observed with such clarity(清晰) before.

    It was not an easy task. Sound waves don't travel through water in the uniform, predictable way they do through the air. Instead, the temperature, salinity (盐度) and, flow of water have great effects on their path.

    What can be done? One solution is to change shipping routes to courses where ships are statistically less likely to meet animals. It's also possible to slow ships down to 18km/h or less, which is less likely to seriously injure a whale.

    As for dealing with the root cause of the problem, the UN's International Maritime Organisation has already published guidelines on how to quieten ships, but it will be a while before the effects of such changes might be observed.

    "The ocean is not our world," comments Andre. But it is ours to look after. And thanks to his work, we can better understand the effects of subsea sound pollution.

Emilia Dobek traces her interest in space and the universe back to third grade when she and her father watched a blood moon — a total lunar eclipse (月食) — on the roof of their house.

Now a seventh grader at East Prairie Elementary School, Dobek recently won the national Discovery Education Lockheed Martin Beyond Challenge by designing a space station for travelling to Mars.

She says that night watching the lunar eclipse started a strong desire in her that has yet to run out of fuel. So when her teacher Andrea Smeeton received information about the national challenge, Smeeton said she immediately had one student in mind.

"I knew she would love the challenge and that she would go way beyond in her search," Smeeton said. "She immediately started researching bone density (密度) of astronauts and how to have food on Mars. "

"My design will ensure the safety of the astronauts and make sure their comfort is out of this world," Dobek says.

Dobek's design calls for building the MSS or Mars Storage Station to put the supplies in. It also includes the SGF or Self-Growing Farm, and she details how it would work with the elements on Mars.

Then there is physical and leisure activity for the astronauts under Dobek's design. A simulator (模拟装置) allows astronauts to choose their exercise machine and virtual reality environment. Rooms have circular ceilings so astronauts will be able to watch downloaded shows and even see places on Earth, such as their homes.

"I want to tell other kids to follow their passions," Dobek said. "Whatever they want to do, they should push for it and always try their best."