Frozen Carbon Dioxide Frozen Carbon Dioxide Name: Paul Status: student Age: 30s Location: N/A Country: N/A Date: 2000 Question: What is the temperature and internal energy (BTU/Lbmol) for solid carbon dixide (dry ice)? Replies: Paul : Carbon dioxide (CO2) exists as a solid over a range of temperatures and pressures. The solid phase field is bounded by the melting curve (solid --> liquid) and the sublimation curve (solid --> gas). Since the internal energy is a function of both temperature and pressure, it's difficult to give an answer to your question. Can you provide some further details ? Jim What Is Dry Ice? What Is Dry Ice? Dry Ice and Carbon Dioxide These pellets of dry ice are sublimating in air. Richard Wheeler Updated September 19, 2015. Question: What Is Dry Ice? Is It Dangerous? Answer: Dry ice is the common name for the solid form of carbon dioxide. Originally the term ' dry ice ' was a trademark for the solid carbon dioxide produced by Prest Air Devices (1925), but now it refers to any solid carbon dioxide . Carbon dioxide is a natural component of air.

Dry ice is safe to use for smoke machines and lab experiments, providing care is taken to avoid frostbite. Why Is it Called Dry Ice? It's called dry ice because it doesn't melt into a wet liquid. Dry ice sublimates, which means it goes from its solid form directly to its gaseous form. Since it's never wet, it must be dry! How Is Dry Ice Made? Dry ice is made by compressing carbon dioxide gas until it liquefies, which is at about 870 pounds per square inch of pressure at room temperature . When the pressure is released, some of the liquid will transition into a gas, cooling some of the liquid into dry ice frost or snow, which can be collected and pressed into pellets or blocks. continue reading below our video 4 Tips for Improving Test Performance This is similar to what happens when you get frost on the nozzle of a CO2 fire extinguisher. The freezing point of carbon dioxide is -109.3°F or -78.5° C, so dry ice won't stay solid for long at room temperature. What Are Some Uses of Dry Ice? Dry ice is used to create smoke and fog special effects .

Dry ice is used to freeze and refrigerate items that need to be kept cold. One advantage of using dry ice to cold-pack goods is that it does not melt and make a mess as it warms. Dry ice can blast-clean industrial equipment. Dry ice can be used to seed clouds to induce precipitation. About Carbon Dioxide From Wikipedia, the free encyclopedia Carbon dioxide is used by plants during photosynthesis to make sugars which may either be consumed again in respiration or used as the raw material to produce polysaccharides such as starch and cellulose , proteins and the wide variety of other organic compounds required for plant growth and development. It is produced during respiration by plants, and by all animals, fungi and microorganisms that depend on living and decaying plants for food, either directly or indirectly. It is, therefore, a major component of the carbon cycle . Carbon dioxide is generated as a by-product of the combustion of fossil fuels or the burning of vegetable matter, among other chemical processes. Over very long time scales (thousands to millions of years), concentrations are influenced by emissions from volcanoes and other geothermal processes such as hot springs and geysers and by the dissolution of carbonates in crustal rocks.

Carbon dioxide has no liquid state at pressures below 5.1 atm . At 1 atm it is a solid at temperatures below −78 °C. In its solid state, carbon dioxide is commonly called dry ice . CO2 is an acidic oxide : an aqueous solution turns litmus from blue to pink. CO2 in concentrations of 7% to 10% cause dizziness, headache, visual and hearing dysfunction, and unconsciousness within a few minutes to an hour [2] . [ edit ] Chemical and physical properties Carbon dioxide pressure-temperature phase diagram showing the triple point and critical point of carbon dioxide For more details on this topic, see Carbon dioxide (data page) . Carbon dioxide is a colourless, odorless gas. When inhaled at concentrations much higher than usual atmospheric levels, it can produce a sour taste in the mouth and a stinging sensation in the nose and throat. These effects result from the gas dissolving in the mucous membranes and saliva , forming a weak solution of carbonic acid . This sensation can also occur during an attempt to stifle a burp after drinking a carbonated beverage .

Amounts above 5,000 ppm are considered very unhealthy, and those above about 50,000 ppm (equal to 5% by volume) are considered dangerous to animal life. [3] At standard temperature and pressure , the density of carbon dioxide is around 1.98 kg/m3, about 1.5 times that of air . The carbon dioxide molecule (O=C=O) contains two double bonds and has a linear shape. It has no electrical dipole , and as it is fully oxidized , it is moderately reactive and is non-flammable, but will support the combustion of metals such as magnesium . Small pellets of dry ice subliming in air. Crystal structure of dry ice At −78.51 ° C or −109.3 ° F , carbon dioxide changes directly from a solid phase to a gaseous phase through sublimation , or from gaseous to solid through deposition . Solid carbon dioxide is normally called " dry ice ", a generic trademark . It was first observed in 1825 by the French chemist Charles Thilorier . Dry ice is commonly used as a cooling agent, and it is relatively inexpensive.

A convenient property for this purpose is that solid carbon dioxide sublimes directly into the gas phase leaving no liquid. It can often be found in grocery stores and laboratories, and it is also used in the shipping industry. The largest non-cooling use for dry ice is blast cleaning . Liquid carbon dioxide forms only at pressures above 5.1 atm; the triple point of carbon dioxide is about 518 kPa at −56.6 °C (See phase diagram, above). The critical point is 7.38 MPa at 31.1 °C. [4] An alternative form of solid carbon dioxide, an amorphous glass-like form, is possible, although not at atmospheric pressure. [5] This form of glass, called carbonia , was produced by supercooling heated CO2 at extreme pressure (40–48 GPa or about 400,000 atmospheres) in a diamond anvil . This discovery confirmed the theory that carbon dioxide could exist in a glass state similar to other members of its elemental family, like silicon ( silica glass ) and germanium .

Unlike silica and germania glasses, however, carbonia glass is not stable at normal pressures and reverts back to gas when pressure is released. See also: Supercritical carbon dioxide and dry ice [ edit ] History of human understanding Carbon dioxide was one of the first gases to be described as a substance distinct from air. In the seventeenth century, the Flemish chemist Jan Baptist van Helmont observed that when he burned charcoal in a closed vessel, the mass of the resulting ash was much less than that of the original charcoal. His interpretation was that the rest of the charcoal had been transmuted into an invisible substance he termed a "gas" or "wild spirit" (spiritus sylvestre). The properties of carbon dioxide were studied more thoroughly in the 1750s by the Scottish physician Joseph Black . He found that limestone ( calcium carbonate ) could be heated or treated with acids to yield a gas he called "fixed air." He observed that the fixed air was denser than air and did not support either flame or animal life. Black also found that when bubbled through an aqueous solution of lime ( calcium hydroxide ), it would precipitate calcium carbonate.

He used this phenomenon to illustrate that carbon dioxide is produced by animal respiration and microbial fermentation. In 1772, English chemist Joseph Priestley published a paper entitled Impregnating Water with Fixed Air in which he described a process of dripping sulfuric acid (or oil of vitriol as Priestley knew it) on chalk in order to produce carbon dioxide, and forcing the gas to dissolve by agitating a bowl of water in contact with the gas. [6] Carbon dioxide was first liquefied (at elevated pressures) in 1823 by Humphry Davy and Michael Faraday . [7] The earliest description of solid carbon dioxide was given by Charles Thilorier , who in 1834 opened a pressurized container of liquid carbon dioxide, only to find that the cooling produced by the rapid evaporation of the liquid yielded a "snow" of solid CO2. [8] [ edit ] Isolation and production Carbon dioxide may be obtained from air distillation . However, this yields only very small quantities of CO2. A large variety of chemical reactions yield carbon dioxide, such as the reaction between most acids and most metal carbonates.

For example, the reaction between hydrochloric acid and calcium carbonate (limestone or chalk) is depicted below: 2 HCl + CaCO3 → CaCl2 + H2CO3 The H2CO3 then decomposes to water and CO2. Such reactions are accompanied by foaming or bubbling, or both. In industry such reactions are widespread because they can be used to neutralize waste acid streams. The production of quicklime (CaO) a chemical that has widespread use, from limestone by heating at about 850 °C also produces CO2: CaCO3 → CaO + CO2 The combustion of all carbon containing fuels, such as methane ( natural gas ), petroleum distillates ( gasoline , diesel , kerosene , propane ), but also of coal and wood, will yield carbon dioxide and, in most cases, water. As an example the chemical reaction between methane and oxygen is given below.

CH4 + 2 O2 → CO2 + 2 H2O Iron is reduced from its own oxides with coke in a blast furnace , producing pig iron and carbon dioxide: 2 Fe2O3 + 3 C → 4 Fe + 3 CO2 Yeast metabolizes sugar to produce carbon dioxide and ethanol , also known as alcohol, in the production of wines, beers and other spirits, but also in the production of bioethanol : C6H12O6 → 2 CO2 + 2 C2H5OH All aerobic organisms produce CO2 when they oxidize carbohydrates , fatty acids , and proteins in the mitochondria of cells. The large number of reactions involved are exceedingly complex and not described easily. Refer to ( cellular respiration , anaerobic respiration and photosynthesis ). Photoautotrophs (i.e. plants, cyanobacteria ) use another modus operandi: Plants absorb CO2 from the air, and, together with water, react it to form carbohydrates: nCO2 + nH2O → (CH2O)n + nO2 Carbon dioxide is soluble in water, in which it spontaneously interconverts between CO2 and H2CO3 ( carbonic acid ).

The relative concentrations of CO2, H2CO3, and the deprotonated forms HCO3− ( bicarbonate ) and CO32−( carbonate ) depend on the pH . In neutral or slightly alkaline water (pH > 6.5), the bicarbonate form predominates (>50%) becoming the most prevalent (>95%) at the pH of seawater, while in very alkaline water (pH > 10.4) the predominant (>50%) form is carbonate. The bicarbonate and carbonate forms are very soluble, such that air-equilibrated ocean water (mildly alkaline with typical pH = 8.2 – 8.5) contains about 120 mg of bicarbonate per liter. [ edit ] Uses Carbon dioxide bubbles in a soft drink. Carbon dioxide is used by the food industry, the oil industry, and the chemical industry.

[9] It is used in many consumer products that require pressurized gas because it is inexpensive and nonflammable, and because it undergoes a phase transition from gas to liquid at room temperature at an attainable pressure of approximately 60 bar (870 psi, 59 atm), allowing far more carbon dioxide to fit in a given container than otherwise would. Life jackets often contain canisters of pressured carbon dioxide for quick inflation. Aluminum capsules are also sold as supplies of compressed gas for airguns , paintball markers, for inflating bicycle tires, and for making seltzer . Rapid vaporization of liquid carbon dioxide is used for blasting in coal mines. High concentrations of carbon dioxide can also be used to kill pests, such as the Common Clothes Moth . [ edit ] Drinks Carbon dioxide is used to produce carbonated soft drinks and soda water . Traditionally, the carbonation in beer and sparkling wine comes about through natural fermentation, but some manufacturers carbonate these drinks artificially. [ edit ] Foods A candy called Pop Rocks is pressurized with carbon dioxide gas at about 40 bar (600 psi).

When placed in the mouth, it dissolves (just like other hard candy) and releases the gas bubbles with an audible pop. Leavening agents produce carbon dioxide to cause dough to rise. Baker's yeast produces carbon dioxide by fermentation of sugars within the dough, while chemical leaveners such as baking powder and baking soda release carbon dioxide when heated or if exposed to acids . [ edit ] Pneumatic systems Carbon dioxide is the most commonly used compressed gas for pneumatic systems in portable pressure tools and combat robots . [ edit ] Fire extinguisher Carbon dioxide extinguishes flames, and some fire extinguishers , especially those designed for electrical fires, contain liquid carbon dioxide under pressure. Carbon dioxide has also been widely used as an extinguishing agent in fixed fire protection systems for total flooding of a protected space, (National Fire Protection Association Code 12). International Maritime Organisation standards also recognise carbon dioxide systems for fire protection of ship holds and engine rooms. Carbon dioxide based fire protection systems have been linked to several deaths.

A review of CO2 systems (Carbon Dioxide as a Fire Suppressant: Examining the Risks, US EPA) identified 51 incidents between 1975 and the date of the report, causing 72 deaths and 145 injuries. [ edit ] Welding Carbon dioxide also finds use as an atmosphere for welding , although in the welding arc, it reacts to oxidize most metals. Use in the automotive industry is common despite significant evidence that welds made in carbon dioxide are brittler than those made in more inert atmospheres, and that such weld joints deteriorate over time because of the formation of carbonic acid. It is used as a welding gas primarily because it is much less expensive than more inert gases such as argon or helium . [ edit ] Caffeine removal Liquid carbon dioxide is a good solvent for many lipophilic organic compounds , and is used to remove caffeine from coffee . First, the green coffee beans are soaked in water. The beans are placed in the top of a column seventy feet (21 m) high. Then super-pressurized carbon dioxide in fluid form at about 93 degrees Celsius enters at the bottom of the column.

The caffeine diffuses out of the beans and into the carbon dioxide. [ edit ] Pharmaceutical and other chemical processing Carbon dioxide has begun to attract attention in the pharmaceutical and other chemical processing industries as a less toxic alternative to more traditional solvents such as organochlorides . It's used by some dry cleaners for this reason. (See green chemistry .) In the chemical industry, carbon dioxide is used for the production of urea , carbonates and bicarbonates , and sodium salicylate . [ edit ] Biological applications Plants require carbon dioxide to conduct photosynthesis , and greenhouses may enrich their atmospheres with additional CO2 to boost plant growth, since its low present-day atmosphere concentration is just above the "suffocation" level for green plants. A photosynthesis -related drop in carbon dioxide concentration in a greenhouse compartment can kill green plants. At high concentrations, carbon dioxide is toxic to animal life, so raising the concentration to 10,000 ppm (1%) for several hours can eliminate pests such as whiteflies and spider mites in a greenhouse. It has been proposed that carbon dioxide from power generation be bubbled into ponds to grow algae that could then be converted into biodiesel fuel.

[10] Carbon dioxide is already increasingly used in greenhouses as the main carbon source for Spirulina algae. In medicine, up to 5% carbon dioxide is added to pure oxygen for stimulation of breathing after apnea and to stabilize the O2/CO2 balance in blood. A common type of industrial gas laser is the carbon dioxide laser . [ edit ] Polymers and plastics Please help improve this article or section by expanding it. Further information might be found on the talk page . (December 2008) Carbon dioxide can also be combined with limonene oxide from orange peels or other epoxides to create polymers and plastics. [11] Please help improve this article or section by expanding it. Further information might be found on the talk page . (December 2008) Carbon dioxide is used in enhanced oil recovery where it is injected into or adjacent to producing oil wells, usually under supercritical conditions. It acts as both a pressurizing agent and, when dissolved into the underground crude oil , significantly reduces its viscosity, enabling the oil to flow more rapidly through the earth to the removal well.

[12] In mature oil fields, extensive pipe networks are used to carry the carbon dioxide to the injection points. [ edit ] As refrigerants Liquid and solid carbon dioxide are important refrigerants , especially in the food industry, where they are employed during the transportation and storage of ice cream and other frozen foods. Solid carbon dioxide is called "dry ice" and is used for small shipments where refrigeration equipment is not practical. Liquid carbon dioxide (industry nomenclature R744 / R-744) was used as a refrigerant prior to the discovery of R-12 . Its physical properties are highly favorable for cooling, refrigeration, and heating purposes, having a high volumetric cooling capacity. Due to their operation at pressures of up to 130 bars, CO2 systems require highly resistant components that have been already developed to serial production in many sectors. This article or section contains weasel words , vague phrasing that often accompanies biased or unverifiable information. Such statements should be clarified or removed .

(December 2008) Its environmental advantages ( GWP of 1, non-ozone depleting, non-toxic, non-flammable) could make it the future working fluid to replace current HFCs in cars, supermarkets, hot water heat pumps, among others. Some applications: Coca-Cola has fielded CO2-based beverage coolers and the US Army is interested in CO2 refrigeration and heating technology. [13] [14] By the end of 2007, the global car industry is expected to decide on the next-generation refrigerant in car air conditioning. CO2 is one discussed option.(see The Cool War ) [ edit ] Coal bed methane recovery Please help improve this section by expanding it. Further information might be found on the talk page . (December 2008) [ edit ] Wine making Carbon dioxide in the form of dry ice is often used in the wine making process to cool down bunches of grapes quickly after picking to help prevent spontaneous fermentation by wild yeasts .

The advantage of using dry ice over regular water ice is that it cools the grapes without adding any additional water that may decrease the sugar concentration in the grape must , and therefore also decrease the alcohol concentration in the finished wine. Dry ice is also used during the cold soak phase of the wine making process to keep grapes cool. The carbon dioxide gas that results from the sublimation of the dry ice tends to settle to the bottom of tanks because it is heavier than regular air. The settled carbon dioxide gas creates an hyoxic environment which helps to prevent bacteria from growing on the grapes until it is time to start the fermentation with the desired strain of yeast. Carbon dioxide is also used to create a hypoxic environment for carbonic maceration , the process used to produce Beaujolais wine. Carbon dioxide is sometimes used to top up wine bottles or other storage vessels such as barrels to prevent oxidation, though it has the problem that it can dissolve into the wine, making a previously still wine slightly fizzy. For this reason, other gasses such as nitrogen or argon are preferred for this process by professional wine makers.

[ edit ] In the Earth's atmosphere Main article: Carbon dioxide in the Earth's atmosphere Carbon dioxide in earth's atmosphere is considered a trace gas currently occurring at an average concentration of about 385 parts per million by volume or 582 parts per million by mass. [16] The mass of the Earth atmosphere is 5.14×1018 kg [17] , so the total mass of atmospheric carbon dioxide is 3.0×1015 kg (3,000 gigatonnes). Atmospheric concentrations of carbon dioxide fluctuate slightly with the change of the seasons, driven primarily by seasonal plant growth in the Northern Hemisphere . Concentrations of carbon dioxide fall during the northern spring and summer as plants consume the gas, and rise during the northern autumn and winter as plants go dormant, die and decay (see graph at right). Concentrations also vary considerably on a regional basis: in urban areas it is generally higher and indoors it can reach 10 times the background atmospheric concentration. Carbon dioxide is a greenhouse gas . See greenhouse effect for more.

Yearly increase of atmospheric CO2: In the 1960s, the average annual increase was 37% of the 2000–2007 average. [18] Due to human activities such as the combustion of fossil fuels and deforestation , the concentration of atmospheric carbon dioxide has increased by about 35% since the beginning of the age of industrialization . [19] In 1999, 2,244,804,000 (=~2.2×109) metric tons of CO2 were produced in the U.S. as a result of electric energy generation. This is an output rate of 0.6083 kg (1.341 pounds) per kWh. [20] Five hundred million years ago carbon dioxide was 20 times more prevalent than today, decreasing to 4–5 times during the Jurassic period and then maintained a slow decline until the industrial revolution , with a particularly swift reduction occurring 49 million years ago. [21] [22] Up to 40% of the gas emitted by some volcanoes during subaerial volcanic eruptions is carbon dioxide.

[23] According to the best estimates, volcanoes release about 130-230 million tonnes (145-255 million tons) of CO2 into the atmosphere each year. Carbon dioxide is also produced by hot springs such as those at the Bossoleto site near Rapolano Terme in Tuscany, Italy. Here, in a bowl-shaped depression of about 100 m diameter, local concentrations of CO2 rise to above 75% overnight, sufficient to kill insects and small animals, but warm rapidly when sunlit and disperse by convection during the day [24] Locally high concentrations of CO2, produced by disturbance of deep lake water saturated with CO2 are thought to have caused 37 fatalities at Lake Monoun , Cameroon in 1984 and 1700 casualties at Lake Nyos , Cameroon in 1986. [25] However, emissions of CO2 by human activities are currently more than 130 times greater than the quantity emitted by volcanoes, amounting to about 27 billion tonnes per year.

[26] [ edit ] In the oceans There is about 50 times as much carbon dissolved in the oceans in the form of CO2 and CO2 hydration products as exists in the atmosphere. The oceans act as an enormous carbon sink , having "absorbed about one-third of all human-generated CO2 emissions to date." [27] Generally, gas solubility decreases as water temperature increases. Accordingly the ability of the oceans to absorb carbon dioxide from the atmosphere decreases as ocean temperatures rise. Most of the CO2 taken up by the ocean forms carbonic acid. Some is consumed in photosynthesis by organisms in the water, and a small proportion of that sinks and leaves the carbon cycle. There is considerable concern that as a result of increased CO2 in the atmosphere the acidity of seawater has been increasing and may adversely affect organisms living in the water. In particular, with increasing acidity, the availability of carbonates for forming shells decreases. [28] [ edit ] Biological role Carbon dioxide is an end product in organisms that obtain energy from breaking down sugars, fats and amino acids with oxygen as part of their metabolism , in a process known as cellular respiration . This includes all plants, animals, many fungi and some bacteria.

In higher animals, the carbon dioxide travels in the blood from the body's tissues to the lungs where it is exhaled. In plants using photosynthesis, carbon dioxide is absorbed from the atmosphere. [ edit ] Role in photosynthesis Plants remove carbon dioxide from the atmosphere by photosynthesis, also called carbon assimilation , which uses light energy to produce organic plant materials ( cellulose ) by combining carbon dioxide and water. Free oxygen is released as gas from the decomposition of water molecules, while the hydrogen is split into its protons and electrons and used to generate chemical energy via photophosphorylation . This energy is required for the fixation of carbon dioxide in the Calvin cycle to form sugars. These sugars can then be used for growth within the plant through respiration. Even when vented, carbon dioxide must be introduced into greenhouses to maintain plant growth, as the concentration of carbon dioxide can fall during daylight hours to as low as 200 ppm. Plants can potentially grow up to 50 percent faster in concentrations of 1,000 ppm CO2 when compared with ambient conditions. [29] Plants also emit CO2 during respiration, so it is only during growth stages that plants are net absorbers.

For example a growing forest will absorb many tons of CO2 each year, however a mature forest will produce as much CO2 from respiration and decomposition of dead specimens (e.g. fallen branches) as used in biosynthesis in growing plants. [30] Regardless of this, mature forests are still valuable carbon sinks , helping maintain balance in the Earth's atmosphere. Additionally, and crucially to life on earth, phytoplankton photosynthesis absorbs dissolved CO2 in the upper ocean and thereby promotes the absorption of CO2 from the atmosphere. [31] [ edit ] Toxicity Carbon dioxide content in fresh air (averaged between sea-level and 10 hPa level, i.e. about 30 km altitude) varies between 0.036% (360 ppm) and 0.039% (390 ppm), depending on the location (see graphical map of CO2 ). According to the Australian Maritime Safety Authority, "Prolonged exposure to moderate concentrations can cause acidosis and adverse effects on calcium phosphorus metabolism resulting in increased calcium deposits in soft tissue. Carbon dioxide is toxic to the heart and causes diminished contractile force.

At concentrations of three per cent by volume in air, it is mildly narcotic and causes increased blood pressure and pulse rate, and causes reduced hearing. At concentrations of about five per cent by volume it causes stimulation of the respiratory centre, dizziness, confusion and difficulty in breathing accompanied by headache and shortness of breath. At about eight per cent concentration it causes headache, sweating, dim vision, tremor and loss of consciousness after exposure for between five and ten minutes." [32] A natural disaster linked to CO2 intoxication occurred during the limnic eruptions in the CO2-rich lakes of Monoun and Nyos in the Okun range of North-West Cameroon : the gas was brutally expelled from the mountain lakes and leaked into the surrounding valleys, killing most animal forms. During the Lake Nyos tragedy of 1986, 1700 villagers and 3500 livestock died. [33] Due to the health risks associated with carbon dioxide exposure, the U.S. Occupational Safety and Health Administration says that average exposure for healthy adults during an eight-hour work day should not exceed 5,000 ppm (0.5%).

The maximum safe level for infants, children, the elderly and individuals with cardio-pulmonary health issues is significantly less. For short-term (under ten minutes) exposure, the U.S. National Institute for Occupational Safety and Health (NIOSH) and American Conference of Government Industrial Hygienists (ACGIH) limit is 30,000 ppm (3%). NIOSH also states that carbon dioxide concentrations exceeding 4% are immediately dangerous to life and health. [34] Adaptation to increased levels of CO2 occurs in humans. Continuous inhalation of CO2 can be tolerated at three percent inspired concentrations for at least one month and four percent inspired concentrations for over a week. It was suggested that 2.0 percent inspired concentrations could be used for closed air spaces (ex. Submarine ) since the adaptation is physiological and reversible. Decrement in performance or in normal physical activity does not happen at this level. [35] [36] These figures are valid for pure carbon dioxide. In indoor spaces occupied by people the carbon dioxide concentration will reach higher levels than in pure outdoor air.

Concentrations higher than 1,000 ppm will cause discomfort in more than 20% of occupants, and the discomfort will increase with increasing CO2 concentration. The discomfort will be caused by various gases coming from human respiration and perspiration, and not by CO2 alone. At 2,000 ppm the majority of occupants will feel a significant degree of discomfort, and many will develop nausea and headaches. The CO2 concentration between 300 and 2,500 ppm is used as an indicator of indoor air quality. Acute carbon dioxide toxicity is sometimes known by the names given to it by miners: blackdamp (also called choke damp or stythe). Miners would try to alert themselves to dangerous levels of carbon dioxide in a mine shaft by bringing a caged canary with them as they worked. The canary would inevitably die before CO2 reached levels toxic to people. (The canary would also indicate dangerous levels of methane and other gases by the same principle.) Carbon dioxide ppm levels (CDPL) are a surrogate for measuring indoor pollutants that may cause occupants to grow drowsy, get headaches, or function at lower activity levels.

To eliminate most Indoor Air Quality complaints, total indoor CDPL must be reduced to below 600. NIOSH considers that indoor air concentrations that exceed 1,000 are a marker suggesting inadequate ventilation. ASHRAE recommends they not exceed 1,000 inside a space. See also: Arterial blood gas CO2 is carried in blood in three different ways. (The exact percentages vary depending whether it is arterial or venous blood). Most of it (about 70% – 80%) is converted to bicarbonate ions HCO3− by the enzyme carbonic anhydrase in the red blood cells, [37] by the reaction CO2 + H2O → H2CO3 → H+ + HCO3−. 5% – 10% is dissolved in the plasma [37] 5% – 10% is bound to hemoglobin as carbamino compounds [37] Hemoglobin , the main oxygen-carrying molecule in red blood cells , carries both oxygen and carbon dioxide. However, the CO2 bound to hemoglobin does not bind to the same site as oxygen. Instead, it combines with the N-terminal groups on the four globin chains.

However, because of allosteric effects on the hemoglobin molecule, the binding of CO2 decreases the amount of oxygen that is bound for a given partial pressure of oxygen. The decreased binding to carbon dioxide in the blood due to increased oxygen levels is known as the Haldane Effect , and is important in the transport of carbon dioxide from the tissues to the lungs. Conversely, a rise in the partial pressure of CO2 or a lower pH will cause offloading of oxygen from hemoglobin, which is known as the Bohr Effect . Carbon dioxide is one of the mediators of local autoregulation of blood supply. If its levels are high, the capillaries expand to allow a greater blood flow to that tissue. Bicarbonate ions are crucial for regulating blood pH. A person's breathing rate influences the level of CO2 in their blood. Breathing that is too slow or shallow causes respiratory acidosis , while breathing that is too rapid leads to hyperventilation , which may cause respiratory alkalosis . Although the body requires oxygen for metabolism, low oxygen levels do not stimulate breathing. Rather, breathing is stimulated by higher carbon dioxide levels.

As a result, breathing low-pressure air or a gas mixture with no oxygen at all (such as pure nitrogen) can lead to loss of consciousness without ever experiencing air hunger . This is especially perilous for high-altitude fighter pilots. It is also why flight attendants instruct passengers, in case of loss of cabin pressure, to apply the oxygen mask to themselves first before helping others — otherwise one risks going unconscious. [37] Typically the gas we exhale is about 4% to 5% carbon dioxide and 4% to 5% less oxygen than was inhaled. According to a study by the United States Department of Agriculture , an average person's respiration generates approximately 450 liters (roughly 900 grams) of carbon dioxide per day. [38] Carbon Dioxide | UCAR Center for Science Education Home Carbon Dioxide Four representations chemists use for carbon dioxide. In the colored models, carbon is light gray and oxygen is red. Credit: Randy Russell (©2006 NESTA) Carbon dioxide is a colorless and non-flammable gas at normal temperature and pressure. Although much less abundant than nitrogen and oxygen in Earth's atmosphere , carbon dioxide is an important constituent of our planet's air.

A molecule of carbon dioxide (CO2) is made up of one carbon atom and two oxygen atoms. Carbon dioxide is an important greenhouse gas that helps to trap heat in our atmosphere. Without it, our planet would be inhospitably cold. However, a gradual increase in CO2 concentrations in Earth's atmosphere is helping to drive global warming, threatening to disrupt our planet's climate as average global temperatures gradually rise. Carbon dioxide is the fourth most abundant component of dry air. It has a concentration of about 400 ppmv (parts per million by volume) in Earth's atmosphere. Scientists estimate that before human industrial activity, CO2 concentration was around 270 ppmv. Carbon dioxide levels in our atmosphere have thus risen about 40% since the onset of human industrialization, and are expected to play a troubling role in raising global temperature. Atmospheric carbon dioxide concentrations have varied substantially in the pre-human history of our planet, and have had profound impacts on global temperatures in the past. Carbon dioxide plays a key role in Earth's carbon cycle , the set of processes that cycle carbon in many forms throughout our environment. Volcanic outgassing and wildfires are two significant natural sources of CO2 in Earth's atmosphere.

Respiration, the process by which organisms liberate energy from food, emits carbon dioxide. When you exhale, it is carbon dioxide (amongst other gases) that you breathe out. Combustion, whether in the guise of wildfires, as a result of slash-and-burn agricultural practices, or in internal combustion engines, produces carbon dioxide. Photosynthesis, the biochemical process by which plants and some microbes create food, uses up carbon dioxide. Photosynthetic organisms combine CO2 and water (H2O) to produce carbohydrates (such as sugars) and emit oxygen as a by-product. Places such as forests and areas of the ocean that support photosynthetic microbes therefore act as massive carbon "sinks", removing carbon dioxide from the atmosphere via photosynthesis. Earth's early atmosphere had much higher CO2 levels and almost no oxygen; the rise of photosynthetic organisms led to an increase in oxygen which enabled the development of oxygen-breathing creatures such as us! Burning generates CO2, although incomplete combustion due to limited oxygen supply or an excess of carbon can also produce carbon monoxide (CO). Carbon monoxide, a dangerous pollutant, eventually oxidizes to carbon dioxide.

Small canisters containing pressurized CO2 are used to inflate bicycle tires and life jackets and to power paintball guns. The "fizz" in soda pop is supplied by carbon dioxide. Carbon dioxide is also released by yeast during fermentation, giving beer its head and making champagne bubbly. Because it is not flammable, CO2 is used in some fire extinguishers. Carbon dioxide forms a weak acid, called carbonic acid (H2CO3), when dissolved in water. Carbon dioxide is the most abundant gas in the atmospheres of Mars and Venus. Solid, frozen carbon dioxide is called "dry ice". The polar ice caps of Mars are a mixture of normal water ice and dry ice. Liquid CO2 only forms at pressures higher than about 5 times the atmospheric pressure on Earth at sea level, so in many situations dry ice does not melt into a liquid form. Instead, it goes directly from a solid state to a gaseous state in a process called sublimation. © 2006 NESTA with modifications by UCAR UCSB Science Line UCSB Science Line Why is it that dry ice is colder than regular ice? What different "elements" make it colder?

Answer 1: Regular ice is made from freezing water. Water freezes at zero degrees Celsius, or +32 degrees Fahrenheit. (Most of Europe and all scientists use Celsius because we're lazy and it's easier, but the US is still stuck on the Fahrenheit temperature scale.) "Dry ice" is made from frozen carbon dioxide gas. Carbon dioxide is an odd substance because at regular pressure, it is only found in gas and solid forms: the stuff in the air you breathe and dry ice. So when dry ice "melts" it goes directly into the gas form!At really high pressures, carbon dioxide does form a liquid phase. Anyway, dry ice is much, much colder because carbon dioxide freezes at a lower temperature:-79 degrees Celsius or -109 degrees Fahrenheit! It's very dangerous to handle dry ice because it will freeze your skin and cause frost bite in less than a minute, causing a painful "dry ice burn". Did you know that in Antarctica,the air can sometimes get so cold that the carbon dioxide in the air will freeze, turning into dry ice? This makes it very hard to breathe the air, because without carbon dioxide, our brain doesn't know when to make our body take a breath.

(The brain uses the amount of carbon dioxide in our blood as a signal to breathe rather than the amount of oxygen. Go figure!) Answer 2: Dry ice is made of solid carbon dioxide (CO2) while ice is made, of course, of solid water. Almost all substances have a freezing point which depends on their unique physical and chemical characteristics. I'm not sure,though, how well we understand why a particular substance has the exact melting point it does. Much of the stuff we deal with on a daily basis is solid,meaning that it has a freezing point (transition from liquid to solid) that is higher than "room temperature," or about 20 degrees Celsius A lot of room temp. liquids, such as water, alcohol, and gasoline have freezing points below 20 C but, perhaps, not too far below 0 C. Substances that are normally gases at 20 C and one atmosphere pressure, such as CO2, oxygen, and nitrogen,have much lower freezing points. The temperature of dry ice is around -80 C or 195 K (195 degrees above absolute zero). Oxygen, argon, and nitrogen freeze at around 65 K.

Neon and hydrogen freeze at 10 to 20 K. Normal helium, as it turns out, doesn't ever freeze exactly. One interesting thing about dry ice is that carbon dioxide doesn't exist as a liquid at room temp. and one atmosphere pressure. So dry ice doesn't melt (hence it is "dry") but sublimates - meaning that the CO2 goes directly from solid to vapor as it absorbs heat. The CO2 cylinders that are used to put bubbles in soda are filled with liquid CO2 but have to be pressurized at around 17 atmospheres. Answer 3: Lots of things that are gases at room temperature can be frozen into liquids or solids at cold temperatures. Ice is just water frozen into a solid. Even though dry ice is called "ice", it's not. Dry ice is actually a gas at room temperature - carbon dioxide - frozen into a solid at about -110 degrees. At ice temperatures, carbon dioxide is a gas - and as you probably know is already in the atmosphere and air you breathe.

So if you are playing around with dry ice, you want to make sure to be in a large, well-ventilated room so the carbon dioxide level in the room doesn't get to high as the dry ice melts. By the way, -110 degrees is cold enough to hurt you if you touch it without gloves and definitely shouldn't be tasted (which you probably knew). Something to notice is that dry ice, unlike water, melts directly into a gas without being a liquid. This is called sublimation.There are colder things than dry ice. 70% of all the gas in air is nitrogen. Nitrogen can freeze into a liquid at -320 degrees. Colder than that is liquid helium which has a temperature very close to absolute zero.Thanks for the questions. Answer 4: Dry ice is carbon dioxide ice, not water ice. Carbon dioxide freezes at somewhere around -70 C (I think)whereas water freezes at 0 C.

Water ice can get that cold, of course, but if you have dry ice, it takes energy (and a lot of it) to take something from a solid to a gaseous phase, so it stays at that temperature until it evaporates (carbon dioxide does not form a liquid at atmospheric pressure, no matter how hard you try). As a result, the solid stays at its evaporation temperature. Water, by contrast, heats up to its melting point before plateauing for the same reason. Click Here to return to the search form. Copyright © 2015 The Regents of the University of California, All Rights Reserved. Mars Exploration: Multimedia 6.2MB animation of all four panels Martian South Polar Pits in Layer of Frozen Carbon Dioxide One of the most profound benefits of being able to continue photographing Mars in the Mars Global Surveyor (MGS) Extended Mission is the opportunity to go back and re-image a site that was seen in the previous martian year. New MGS Mars Orbiter Camera (MOC) images have provided a startling observation: The residual martian south polar cap is changing.

The fact that it is changing suggests that Mars may have major, global climate changes that are occurring on the same time scales as Earth's most recent climate shifts, including the last Ice Age. MOC images of the south polar cap taken in 1999 were compared with images of the same locations taken in 2001, and it was discovered that pits had enlarged, mesas had shrunk, and small buttes had vanished. In all, the scarps that enclose the pits and bound the mesas and buttes retreated about 3 meters (3.3 yards) in 1 martian year (687 Earth days). This rapid retreat of polar scarps can only occur if the ice is frozen carbon dioxide (also known as "dry ice"). Retreat of scarps made of water ice is much slower and would not have been measurable from one martian year to the next. The portion of the martian south polar cap that persists through summer is called the residual polar cap. The two sets of four pictures shown here are from four places on the residual south polar cap.

The pictures from 1999 were taken in October of that year, the corresponding pictures from 2001 were acquired in August, approximately 1 Mars year after the 1999 images were obtained. In each case, the pictures are illuminated by sunlight from the upper left, and each shows an area about 250 meters (273 yards) across. The polar cap is layered, and the layers have eroded to form pits, troughs, mesas, and buttes. The pits form as sunlight warms frozen carbon dioxide during southern spring and summer, and the ice sublimes away. There is so much carbon dioxide that it does not all go away in one summer---in fact, it may take hundreds to thousands of years to disappear. These new observations indicate that the south polar residual cap is not permanent. It is disappearing, a little bit more each southern spring and summer season. At the present rate, a layer 3 m thick can be completely eroded away in a few tens of martian years.

Since each layer is equivalent to about 1% of the mass of the present atmosphere (which is 95% carbon dioxide), if sufficient carbon dioxide is buried in the south polar cap, the mass of the atmosphere could double in a few hundred to a thousand Mars years. That could lead to profound changes in the environment. For example, it would change how much and where wind erosion would occur, and where and for how long liquid water could survive at or near the surface. It also means that Mars may have been very different in the recent past (perhaps only a few thousands of years ago). On today's Mars, the ice is eroding, but in the past that material had to have been deposited. The martian climate was probably colder, and there was more carbon dioxide in the atmosphere. For some reason, large amounts of carbon dioxide froze at the south pole---one might say that there was a "Martian Ice Age"---and this freezing occurred on a time scale similar to that of the most recent Ice Age on Earth. Mars is changing, and it is changing on a time scale that we can measure and observe.

If all of the carbon dioxide that is being released into the atmosphere from the south polar cap is not freezing out somewhere else, and if it is not being adsorbed into the martian soil, then it must be causing the atmospheric pressure to increase. If this is so, and if one were to assume that the entire known volume of the polar cap is made of carbon dioxide that sublimes at the same rate we see today, then it could increase the martian atmospheric pressure by as much as 10 times, to about 1/10th the density of Earth's atmosphere, in just the next few thousand years. Although this atmosphere would not be breathable, carbon dioxide is a "greenhouse gas" that would cause the global temperature to increase considerably and make it easier for liquid water to persist elsewhere on the planet. Perhaps, just perhaps, a thickening martian atmosphere would eventually make it easier for people to live on Mars. This new MGS MOC discovery is described in a paper published December 7, 2001, in the journal, Science. Read a more detailed discussion of these results (but less detailed than the Science article).

Images Credit: NASA/JPL/Malin Space Science Systems Dry Ice Information - all about dry ice For locations to buy dry ice & Storage Containers Dry Ice is frozen carbon dioxide , a normal part of our earth's atmosphere. It is the gas that we exhale during breathing and the gas that plants use in photosynthesis. It is also the same gas commonly added to water to make soda water. This gas is often captured during industrial processes and recycled to make Dry Ice. Dry Ice is particularly useful for freezing, and keeping things frozen because of its very cold temperature: -109.3°F or -78.5°C. Dry Ice is widely used because it is simple to freeze and easy to handle using insulated gloves. Dry Ice changes directly from a solid to a gas -sublimation- in normal atmospheric conditions without going through a wet liquid stage. Therefore it gets the name "dry ice." As a general rule, Dry Ice will sublimate at a rate of five to ten pounds every 24 hours in a typical ice chest. This sublimation continues from the time of purchase; therefore, pick up Dry Ice as close to the time needed as possible.

Bring an ice chest or some other insulated container to hold the Dry Ice and slow the sublimation rate. Dry Ice sublimates faster than regular ice melts but will extend the life of regular ice. It is best not to store Dry Ice in your freezer because your freezer's thermostat will shut off the freezer due to the extreme cold of the Dry Ice! Of course if the freezer is broken, Dry Ice will save all your frozen goods. Commercial shippers of perishables often use dry ice even for non frozen goods. Dry ice gives more than twice the cooling energy per pound of weight and three times the cooling energy per volume than regular water ice (H2O). It is often mixed with regular ice to save shipping weight and extend the cooling energy of water ice. Sometimes dry ice is made on the spot from liquid CO2. The resulting dry ice snow is packed in the top of a shipping container offering extended cooling without electrical refrigeration equipment and connections. This informative site is supported by the manufacturers and sellers of Dry Ice. Thank you for supporting them.

Share your ideas on our dryiceInfo's: Read more about the dry ice industry from Ken at: DryIceInfoBlog.com Interesting android app for kids showing experiments with dryice science experiments with ice apk Watch Experiments with Dry Ice from Rock-It Science Learn how to transport or ship frozen foods with dry ice See Great Deals on USED Dry Ice Machines at DryIceClassified.com and additional used Cold Jet blastng machines available here How does dry ice work? | HowStuffWorks How does dry ice work? While dry ice looks like it would be cold, it's extremely dangerous to the touch and can cause severe burns. Photographer: Kivig | Agency: Dreamstime.com ­ ­Dry ice is frozen carbon dioxide. A block of dry ice has a surface temperature of -109.3 degrees Fahrenheit (-78.5 degrees C). Dry ice also has the very nice feature of sublimation -- as it breaks down, it turns directly into carbon dioxide gas rather than a liquid. The super-cold temperature and the sublimation feature make dry ice great for refrigeration. For example, if you want to send something frozen across the country, you can pack it in dry ice.

It will be frozen when it reaches its destination, and there will be no messy liquid left over like you would have with normal ice. Up Next What if I touched dry ice? Many people are familiar with liquid nitrogen, which boils at -320 degrees F (-196 degrees C). Liquid nitrogen is fairly messy and difficult to handle. So why is nitrogen a liquid while carbon dioxide is a solid? This difference is caused by the solid-liquid-gas features of nitrogen and carbon dioxide. ­We are all familiar with the solid-liquid-gas behavior of water. We know that at sea level , water freezes at 32 degrees F (0 degrees C) and boils at 212 degrees F (100 degrees C). Water behaves differently as you change the pressure, however. As you lower the pressure, the boiling point falls. If you lower the pressure enough, water will boil at room temperature. If you plot out the solid-liquid-gas behavior of a substance like water on a graph showing both temperature and pressure, you create what's called a phase diagram for the substance. The phase diagram shows the temperatures and pressures at which a substance changes between solid, liquid and gas.

This page shows the phase diagrams for water and carbon dioxide. What you can see is that, at normal pressures, carbon dioxide moves straight between gas and solid. It is only at much higher pressures that you find liquid carbon dioxide. For example, a high-pressure tank of carbon dioxide or a carbon-dioxide fire extinguisher contains liquid carbon dioxide. To make dry ice, you start with a high-pressure container full of liquid carbon dioxide. When you release the liquid carbon dioxide from the tank, the expansion of the liquid and the high-speed evaporation of carbon dioxide gas cools the remainder of the liquid down to the freezing point, where it turns directly into a solid. If you have ever seen a carbon-dioxide fire extinguisher in action, you have seen this carbon-dioxide snow form in the nozzle. You compress the carbon-dioxide snow to create a block of dry ice. Dry Ice Safety If you ever have a chance to handle dry ice, you want to be sure to wear heavy gloves. The super-cold surface temperature can easily damage your skin if you touch it directly. For the same reason, you never want to taste or swallow dry ice, either. Another important concern with dry ice is ventilation.

You want to make sure the area is well-ventilated. Carbon dioxide is heavier than air, and it can concentrate in low areas or enclosed spaces (like a car or a room where dry ice is sublimating). Normal air is 78% nitrogen, 21% oxygen and only 0.035% carbon dioxide. If the concentration of carbon dioxide in the air rises above 5%, carbon dioxide can become toxic. Be sure to ventilate any area that contains dry ice, and do not transport it in a closed vehicle. 1

Question: What is the name of frozen carbon dioxide?
Answer: Dry Ice