Fascynujące zjawiska fizyczne

Evidence: — • authority: 88

New Explanation for the Mpemba effect. The purpose of this study is to check out the involvement of entropy in Mpemba effect. Provided that preheating of the water the cooling duration is reduced, we theoretically show that water gains more entropy when warmed and re-cooled to the original temperature.

Evidence: — • authority: 88

New Explanation for the Mpemba Effect. The purpose of this study is to check out the involvement of entropy in Mpemba effect. Several water samples were cooled down to frozen in order to probe if preheat affects the cooling duration time. We found out that preheating of the water sample the cooling duration was reduced. Given this, we theoretically show that water gains more entropy when warmed and re-cooled to the original temperature.

Evidence: — • authority: 80

In search of a Mpemba effect protocol: Some hot water does cool and freeze faster than cold

Evidence: — • authority: 80

The MPEMBA effect: The freezing times of hot and cold water

Evidence: — • authority: 88

When does hot water freeze faster then cold water? A search for the Mpemba effect. It is possible to consistently observe hot water freezing faster than cold water under certain conditions. All conditions except the initial temperature of water specimens must be the same and remain so during cooling, and the cold water must supercool to a temperature significantly lower than the temperature to which the hot water supercools. For hot water at an initial temperature of >≈80 °C and cold water at <≈20 °C, the cold water must supercool to a temperature of at least ≈5.5 °C, lower than the temperature to which hot water supercools. With these conditions satisfied, we observed initially hot water f…

Evidence: — • authority: 88

Investigating the Mpemba Effect: when hot water freezes faster than cold water. Abstract Under certain conditions a body of hot liquid may cool faster and freeze before a body of colder liquid, a phenomenon known as the Mpemba Effect. An initial difference in temperature of 3.2 °C enabled warmer water to reach 0 °C in 14% less time than colder water. Convection currents in the liquid generate a temperature gradient that causes more rapid heat loss by surface radiation and evaporation than obtains for uniform temperature. This more rapid cooling enables the initially warmer liquid to overtake the cooler liquid, reaching 0 °C earlier and freezing first. Liquid cooling under natural convection…

Evidence: — • authority: 88

The Mpemba effect: When can hot water freeze faster than cold?. We review the Mpemba effect, where initially hot water freezes faster than initially cold water. Although the effect might appear impossible, it has been observed in numerous experiments and was discussed by Aristotle, Francis Bacon, Roger Bacon, and Descartes. It has a rich and fascinating history, including the story of the secondary school student, Erasto Mpemba, who reintroduced the effect to the twentieth century scientific community. The phenomenon is simple to describe and illustrates numerous important issues about the scientific method: the role of skepticism in scientific inquiry, the influence of theory on experiment…

Evidence: — • authority: 72

Thermal balance of a diver occurs when the total heat exchanged between the diver and their surroundings results in a stable temperature of the diver. Ideally this is within the range of normal human body temperature. Thermal status of the diver is the temperature distribution and heat balance of the diver. The terms are frequently used as synonyms. Thermoregulation is the process by which an organism keeps its body temperature within specific bounds, even when the surrounding temperature is significantly different. The internal thermoregulation process is one aspect of homeostasis: a state of dynamic stability in an organism's internal conditions, maintained far from thermal equilibrium wi…

Evidence: — • authority: 72

Blanching is a process in which a food, usually a vegetable or fruit, is partially cooked by first scalding in boiling water, then removing after a brief timed interval, and finally plunging into iced water or placing under cold running water (known as shocking or refreshing) to halt the cooking process. Blanching foods helps reduce quality loss over time. Blanching is often used as a treatment prior to freezing, dehydrating, or canning vegetables or fruits to deactivate enzymes, modify texture, remove the peel and wilt tissue. The inactivation of enzymes preserves colour, flavour, and nutritional value. The process has three stages: preheating, blanching, and cooling. The most common blanc…

Evidence: — • authority: 72

The Leidenfrost effect or film boiling is a physical phenomenon in which a liquid, close to a solid surface of another body that is significantly hotter than the liquid's boiling point, produces an insulating vapor layer that keeps the liquid from boiling rapidly. Because of this repulsive force, a droplet hovers over the surface, rather than making physical contact with it. The effect is named after the German doctor Johann Gottlob Leidenfrost, who described it in A Tract About Some Qualities of Common Water. This is most commonly seen when cooking, when drops of water are sprinkled onto a hot pan. If the pan's temperature is at or above the Leidenfrost point, which is approximately 193 °C…

Evidence: — • authority: 72

Giovanni Marliani was an Italian physicist, doctor, philosopher and astrologer who was born and lived during the Late Medieval period in northern Italy. Marliani specialised in many mathematical fields and lectured on the phenomenon of natural body heat. He was known for experiments attempting to empirically prove that hot water freezes faster than cold water. (The phenomenon known today as the Mpemba effect.)

Evidence: — • authority: 72

The Mpemba effect is the observation that very hot liquids or colloids (such as ice cream) can freeze more quickly than colder ones, for similar volumes and surrounding conditions. The effect is named after Erasto Mpemba, a Tanzanian teenager who studied it scientifically in the 1960s for the first time, along with Denis Osborne. The Mpemba effect was initially observed in only ice cream and water, and later in other colloids. It has also been studied in magnetic alloys, nanomechanical systems, and quantum systems. In some colloids, a "strong" Mpemba effect is observed, where starting in certain hot temperature ranges leads to freezing much faster than starting in a cooler range. The effect…