Ikigai Daily
Menu
WonderScience fact

Water expands when it freezes, making ice less dense than liquid water and allowing it to float.

Physics

Science

The story behind the card

In liquid water, molecules tumble past one another and pack fairly closely. As water freezes, weak attractions between molecules called hydrogen bonds lock them into a hexagonal lattice with a lot of open space, so ice takes up about 9% more room than the same water. That is why frozen pipes burst and why only about a tenth of an iceberg shows above the surface. Liquid water is densest at about 4 °C, so in winter water at that temperature sinks to the bottom of a lake while colder water, and then ice, gathers at the top. The ice acts as a lid that insulates the water beneath, which is why fish and other life can survive the winter in lakes that freeze over. Most substances behave the other way and shrink as they solidify.

Türkçe oku
Su donarken genleşir. Bu yüzden buzun yoğunluğu sıvı sudan düşüktür ve buz suyun üstünde yüzer.

Sıvı suda moleküller birbirinin yanından kayarak hareket eder ve oldukça sık dizilir. Su donarken, moleküller arasındaki hidrojen bağı denen zayıf çekim kuvvetleri onları arada çok boşluk kalan altıgen bir örgüye kilitler; bu yüzden buz, aynı miktardaki sudan yaklaşık %9 daha fazla yer kaplar. Donan boruların patlamasının ve bir buzdağının ancak onda birinin su üstünde görünmesinin nedeni budur. Sıvı su en yoğun hâline 4 °C dolayında ulaşır; kışın bu sıcaklıktaki su gölün dibine çöker, daha soğuk su ve ardından buz yüzeyde toplanır. Buz, alttaki suyu yalıtan bir kapak görevi görür; donan göllerde balıkların ve başka canlıların kışı atlatabilmesi bundandır. Çoğu madde ise tersine, katılaşırken büzülür.

Sources and further reading

Background reading: Water
Get the mobile appAbout our cards

Related cards

These cards share a subject or reading mode with the card above.

WonderHistory

The Industrial Revolution put the clock in charge of the working day. Before factories, most people worked by daylight, the seasons and the task in hand; from the 1770s, mills such as Richard Arkwright's at Cromford in Derbyshire ran day and night in twelve-hour shifts.

The historian E. P. Thompson traced this change in a famous essay of 1967, “Time, Work-Discipline, and Industrial Capitalism”. Farm and craft work, he argued, had been measured by tasks: milking, harvesting, finishing a piece. Factory work was measured in hours. Cromford Mill, opened in 1771, was the world's first water-powered cotton-spinning mill. It started with about 200 workers, most of them women and children, the youngest only seven. Bells rang at 5 in the morning and 5 in the evening, the gates were shut at exactly 6, and anyone late lost that day's pay and was fined another. In industrial towns, where alarm clocks were not yet cheap or reliable, “knocker-ups” were paid a few pence a week to tap on upstairs windows with long poles.

Ikigai DailyRead card
WonderHistory

Less than 66 years, well within a single lifetime, separate the first powered aeroplane flight from the first Moon landing. Orville Wright flew for 12 seconds and 37 metres on 17 December 1903; Apollo 11 landed on the Moon on 20 July 1969.

The Wright brothers, bicycle makers from Dayton, Ohio, flew near Kitty Hawk, North Carolina, and that first hop was shorter than the wingspan of a Boeing 747. What followed came fast. In 1919 John Alcock and Arthur Brown flew non-stop across the Atlantic; in 1927 Charles Lindbergh did it alone, from New York to Paris; and in 1947 Chuck Yeager flew faster than sound. Orville Wright died in 1948, nine years before the Soviet satellite Sputnik opened the space age. Yuri Gagarin orbited the Earth in 1961, and in July 1969 Neil Armstrong took a scrap of the 1903 Flyer's wood and fabric with him to the Moon.

Ikigai DailyRead card
WonderHistory

The Cold War between the United States and the Soviet Union (1947–1991) was fought mostly without direct battles between the two. They competed instead through weapons, science, sport, films, propaganda and the race into space.

George Orwell used the phrase “cold war” in 1945, and the American journalist Walter Lippmann made it popular in 1947. Because nuclear weapons made open war between the superpowers too dangerous, the rivalry spread into other arenas. After the Soviet Union launched the Sputnik satellite in 1957, the United States passed the National Defense Education Act of 1958 to fund science, maths and language teaching. In 1959, at an American exhibition in Moscow, Vice-President Richard Nixon and the Soviet leader Nikita Khrushchev argued about capitalism and communism in a model kitchen, an exchange remembered as the Kitchen Debate. In 1972 in Reykjavík, the American Bobby Fischer beat the Soviet champion Boris Spassky for the world chess title. The Olympics were boycotted in turn: the United States and many allies stayed away from Moscow in 1980, and most of the Soviet bloc from Los Angeles in 1984.

Ikigai DailyRead card
WonderHistory

The Apollo Guidance Computer, which helped steer astronauts to the Moon, was one of the first computers built from integrated circuits: small silicon chips that each carry several electronic components. Until 1965, Apollo was the biggest user of these new chips.

The computer was designed at the MIT Instrumentation Laboratory from 1962 and built by Raytheon, and one flew in every Apollo command module and lunar module. The chip was still a new invention: Jack Kilby and Robert Noyce had made the first ones in 1958 and 1959. MIT used almost a single type throughout, a simple logic circuit designed by Fairchild Semiconductor, repeated thousands of times. According to the Computer History Museum, Apollo bought some 200,000 of them at 20 to 30 dollars each, and by 1965 the Minuteman missile programme had become the bigger buyer. Orders like these kept the young industry going until prices fell: the average chip cost 50 dollars in 1962 and 2.33 dollars in 1968. The Space Race is often credited with GPS too, but GPS was a separate US Department of Defense project, begun in 1973.

Ikigai DailyRead card
WonderHistory

On 12 April 1961 the Soviet cosmonaut Yuri Gagarin, aged 27, became the first human in space. His Vostok 1 spacecraft circled the Earth once, and the flight lasted 108 minutes from launch to landing.

Gagarin, who had trained as a foundry worker before becoming an air force pilot, was launched from Baikonur, in today's Kazakhstan. As the rocket lifted off he called out “Poyekhali!” (“Let's go!”). His orbit took him as high as 327 kilometres. On the way back he ejected from the capsule about 7 kilometres above the ground and came down by his own parachute near Engels, in the Saratov region, where a farm worker and her granddaughter were the first to meet him. Because the record rules of the day required pilots to land inside their craft, the Soviet Union claimed he had, and admitted the truth only in 1971. Gagarin became famous around the world. He died in a training-jet crash in 1968, aged 34. Since 2011 the United Nations has marked 12 April as the International Day of Human Space Flight.

Ikigai DailyRead card
Next card in the archiveSound needs a medium such as air, water or solid matter to travel, so empty space is silent to human ears.Read next →