In this science activity you will get to try some different, common household substances to try and answer this question: What will help a solid ice cube turn into a liquid puddle the fastest? Background Temperature isn't the only thing that affects how a liquid freezes—and melts.
If you've ever made homemade ice cream the old-fashioned way using a hand-crank machine, you probably know that you need ice and salt to freeze the cream mixture. Similarly, if you live in a cold climate, you've probably seen the trucks that salt and sand the streets after a snowfall to prevent ice from building up on the roads.
In both of these instances salt is lowering the freezing point of water, which means that the water needs to be colder to turn from liquid into ice. For the ice cream maker, the temperature of the ice—salt mixture can get much lower than if just using normal ice, and this makes it possible to freeze the ice cream mixture. In a solution there is a solute salt in this example that gets dissolved in a solvent water in this case.
When other substances are mixed with water they may also lower its freezing point. In this science activity you'll investigate how salt, sand and sugar affect water's freezing point. Observations and results Did the ice cube sprinkled with table salt melt the fastest? In this activity you tried adding salt, sugar or sand to ice to see whether the substance would help melt the ice.
In other words, you wanted to test whether these substances could demonstrate freezing point depression, or the lowering of the ice's freezing point so that it melted into a liquid at a lower temperature than normal. You should have seen that the ice cube with salt sprinkled on it melted faster than any of the other cubes. The larger size means the block ice has less surface area exposed to the outside air, slowing ice melt.
Also the inner core of block ice is insulated from the warm outside by the outer part of the block, meaning it melts last. Black ice, sometimes called clear ice, is a thin coating of glaze ice on a surface, especially on roads. The ice itself is not black, but visually transparent, allowing the often black road below to be seen through it.
If you do hit black ice, your first reaction must be to remain calm and avoid overreacting. The general rule is to do as little as possible and allow the car to pass over the ice.
Do not hit the brakes, and try to keep the steering wheel straight. Twelve inches of snow might melt in a few days or in a week or two if it is exposed to direct sunshine and in temperatures above freezing. But that same amount of snow might linger for months if it is in a shady spot. Warm air melts snow by transferring enough heat into the ice to raise the temperature to its melting point. Water does this no more efficiently than air. If the raindrops falling onto a snow pack are colder than the air, then the snow will actually melt more slowly.
The air temperature rises and falls due to a combination of wind, sunshine and cloud cover. The snow melts due to its energy absorbption raising its temperature greater than its melting point. Air temperature is still below freezing as gas does not generally absorb energy at the rate of solids.
The more surface area of snow, the quicker it will melt. This is the reason why a snowman can remain solid while the snow and powder on the nearby ground melts. The higher conductivity means concrete melts snow faster than grassy ground, and the higher thermal capacity means concrete can melt more snow than grassy ground assuming they start at the same temperature. The density of snow is much lower than the density of ice — so the total heat of fusion needed to melt a volume of snow is much lower.
That will mean the snow melts faster than the ice. Dirty snow melts faster than clean snow. Albedo is the percent of incoming solar radiation reflected by a surface. Light colored surfaces, like fresh snow, reflect more radiation than dark surfaces, like dirty snow. Snow is still great, just refrain from eating it!
The study revealed that from just one hour of exposure, the levels of pollutants within the snow increased dramatically, with toxic particles becoming trapped within the small ice particles or dissolved within the pockets of melted snow. A standard 1 ounce cube 30 grams will take 90 to minutes to melt at the same temperature.
Energy can be transferred move from the surroundings to the ice by conduction through the metal or plastic. Ice is a much more solid structure though, allowing for far better heat conduction via microscopic vibration and has more of itself in contact with the ground. Snow is also shinier than ice, reflecting more sunlight. I know that there are several types of snow and this one is packed powder, with a crust that can support someone walking over it but crumbles if stomped on.
The inner parts are powdery and the edges are coarse, crunchy and wet. How dirty the snow is also plays a part since dirt has a much lower heat capacity than ice and absorbs radiation better. This is a close-up of the snow. Would replacing that volume with solid ice at the same temperature last longer than the snow? My intuition says the snow would last longer but I don't know which contributing factor dominates.
The density of snow is much lower than the density of ice - so the total heat of fusion needed to melt a volume of snow is much lower. That will mean the snow melts faster than the ice. The air in the snow does lower the thermal conductivity - but that just means that the little heat from the air can melt the outer layer of snow without having to worry about the effect of snow "deeper inside".
In my experience a significant factor in snow melting is the presence of dirt - small dark particles that absorb energy from sunlight. This is a factor that matters more for snow in the presence of sunlight - it doesn't affect snow in the shade where only the heat from the air plays a role- and that is what I believe you were asking about. Total energy absorbed by ice and snow will not deplete the Sun's energy or slow its delivery. Rate of heat transfer through the surface and through the ice and snow is the issue.
Sum all energy required to bring each molecule to melting point and you find greater total energy required to melt the ice than the snow, as Floris said in his answer. BUT, as the Sun's energy striking the surface is the same for both ice and snow, and will not be depleted for practical purposes , regardless of the total amount absorbed, the rate of energy transfer to and through ice and snow becomes the important factor.
For ice to melt faster than snow, more energy per unit time needs to be transferred into the ice. Some water will melt, and some will evaporate.
Water that evaporates uses energy that otherwise would be available for conduction through ice and snow. But neither sublimation nor evaporation will reduce the energy per unit time delivered by the Sun to the surface. As energy delivered per unit time will not decrease, heat of evaporation and latent heat of sublimation should not affect the rate of heat transfer into ice and snow.
But the rate of evaporation will be greater per unit volume of snow than ice, as there will be greater surface per mole.
But ice has greater number of moles per unit volume. Available energy per unit time is the same for both, so surface area per mole seems to me an important factor. Radiant energy delivered to and through the surface, and water convection via surface water seeping to the interior, may be the dominant methods of heat transfer into ice and snow.
As snow is more porous, I expect convection via water seepage to be more rapid in snow than ice. As the albedo of ice is less than snow, a snow surface reflects more energy than ice.
More radiant energy per unit time penetrates the surface of bare ice than snow. In favor of snow melting faster: a Greater surface area per mole for evaporation, b Greater porosity per mole for water seepage to transfer heat to interior of snow.
In favor of ice melting faster: a Radiant energy can penetrate the clear surface of ice directly to the interior. I'd guess ice will melt faster on a sunny day, while snow will melt faster on a cloudy day, if a ambient air and ground temperatures are the same on both days, b relative humidity is the same on both days.
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