1. Science Ace- Thematic Studies By: Ng Aik Yang(20) 1A1

3. What is dry ice? Basically, dry ice is the solid form of carbon dioxide, which comprises of two oxygen atoms bonded to a single carbon atom.

4. Properties of dry ice At temperatures above −56.4 °C, Carbon dioxide changes from a solid to a gas with no intervening liquid form, through a process called sublimation. The opposite process is called deposition, where dry ice changes from the gas to solid phase. At atmospheric pressure, sublimation or deposition occurs at −78.5 °C. The density of dry ice varies, but usually ranges between about 1.4 and 1.6 g/cm 3. The low temperature and direct sublimation to a gas makes dry ice an effective coolant, since it is colder than water or ice and leaves no residue as it changes state.

5. History of Dry ice The properties of solid carbon dioxide were discovered in the early twentieth century. It was first produced commercially in the 1920s in the United States. Until fairly recently, dry ice was often referred to as hot ice, a reference to the fact that when one touched the cold surface the hand felt burned.

6. How is dry ice produced? First, gases containing a high concentration of carbon dioxide are produced. Such gases can be a byproduct of some other process, such as producing ammonia from nitrogen and natural gas, or large-scale fermentation. Second, carbon dioxide-rich gas is pressurized and refrigerated until it changes into its liquid form. Furthermore, the pressure is reduced. When this occurs some liquid carbon dioxide vaporizes, and this causes a rapid lowering of temperature of the remaining liquid carbon dioxide. The extreme cold causes the liquid to solidify into a snow-like consistency. Finally, the snow-like solid carbon dioxide is compressed into either small pellets or larger blocks of dry ice.

7. How is dry ice produced?

8. Uses of dry ice Keeping food cold for a period of time Some recent developments for its use include: -using the pellets in blasting or cleaning -transporting medical specimens such as hearts, limbs and tissues for reattachment and trasplantation.

9. Fast facts about dry ice No significant chemicals are created in the production of dry ice. Dry ice can be used to loosen asphalt floor tiles or car sound deadening making it easy to pry off. Dry Ice Bombs! Check this out – Dry Ice BombDry Ice Bomb

11. What is liquid nitrogen? Liquid nitrogen is nitrogen in a liquid state at a very low temperature. It is produced industrially by fractional distillation of liquid air. Liquid nitrogen is a colourless clear liquid with density at its boiling point of 0.807 g/mL and a dielectric constant of 1.4.

12. Properties of liquid nitrogen At atmospheric pressure, liquid nitrogen boils at 77 K (−196 °C; −321 °F) and is a cryogenic fluid which can cause rapid freezing on contact with living tissue, which may lead to frostbite. Liquid nitrogen freezes at 63 K (−210 °C; −346 °F). When appropriately insulated from ambient heat, liquid nitrogen can be stored and transported, for example in vacuum flasks. Here, the very low temperature is held constant at 77 K by slow boiling of the liquid, resulting in the evolution of nitrogen gas. Depending on the size and design, the holding time of vacuum flasks ranges from a few hours to a few weeks.

13. Uses of liquid nitrogen store cells at low temperature for laboratory work immersion freezing and transportation of food products coolant for overclocking a central processing unit, a graphics processing unit, or another type of computer hardware freezing water pipes in order to work on them in situations where a valve is not available to block water flow to the work area. making ultra-smooth ice cream.

14. Liquid Nitrogen is FUN! Check these out: http://www.youtube.com/watch?v=DzNIJ7d3 KR0 http://www.youtube.com/watch?v=DzNIJ7d3 KR0 http://www.youtube.com/watch?v=MaxZwsqs tFs&feature=related http://www.youtube.com/watch?v=MaxZwsqs tFs&feature=related

15. Now, what happens if you mix dry ice and liquid nitrogen? http://www.youtube.com/watch?v=ctPbhKldOgA

16. Bibliography http://www.madehow.com/Volume-7/Dry- Ice.html http://www.madehow.com/Volume-7/Dry- Ice.html http://inventors.about.com/od/dstartinventio ns/a/dry_ice.htm http://inventors.about.com/od/dstartinventio ns/a/dry_ice.htm http://en.wikipedia.org/wiki/Dry_ice http://www.britannica.com/EBchecked/topic/ 172281/Dry-Ice http://www.britannica.com/EBchecked/topic/ 172281/Dry-Ice http://en.wikipedia.org/wiki/Liquid_nitrogen

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