Why is ice sometimes clear and ice sometimes white?

Answer 1

Because snow always scatters light, water never does and inclusions in solid ice can do sometimes.

Many gases including carbon dioxide, oxygen, nitrogen, hydrogen are soluble in water. For example the solubility of oxygen & nitrogen in water at room temperature (25 degrees C) is 0.0089 g/litre & 0.0138 g/litre. According to Henry's law, gas solubility in water increases as the temperature decreases. Water droplets at very high altitude with low temperature environment have high solubility for gas. Besides, the small water droplets have very high surface area for gas to dissolve.

Hence, water droplets in cloud are saturated with dissolved gases. When the environment temperature decreases to freezing point, gas which is not soluble in snow gets trapped inside and forms tiny bubbles. The size and the distribution of the tiny bubbles are quite uniform due to small droplet sizes and fast freezing rate. Visible light reflected by tiny bubbles gives white colored snow.

Water is transparent because it doesn't absorb or reflect visible light.

The appearance of cloudy ice normally depends on water properties and the method of making the ice. Tiny bubbles trapped in ice will give white color. Ice normally has size much bigger than water droplets in cloud (low surface area to size ratio). In a cube of water, water near its surface will freeze first. Bubbles will move towards the center of the ice and form a cloudy part at the center.

Water which has undergone processes that remove dissolved gases will not become cloudy ice. For example: deaeration by boiling water at 100 degree C. The reason ice cubes you buy in the market, hotels, and bars are clear is that the freezing takes place in a flow of water over a cold surface. Then the minerals and air are continuously washed away and pure ice forms clear ice cubes.

Sometimes, water or ice is blue colored (ocean or iceberg) because it absorbs slightly more of the red-frequency part of visible light (Insignificant Normally).

References:

Why is Snow White and Water Transparent but Sometimes Ice can be Both? life Chemistry. Retrieved June 19, 2008, from http://life-chemistry.blogspot.com/2008/06/why-is-snow-white-and-water-transparent.html

Air Solubility in Water. The Engineering Tool Box. Retrieved June 19, 2008, from http://www.engineeringtoolbox.com/air-solubility-water-d_639.html

Henry's Law. Wikipedia. Retrieved June 19, 2008, from http://en.wikipedia.org/wiki/Henry\'s_law

And from the completely "romantic", non-scientific perspective:Why is snow white…

A nearly perfect, clear ice crystal forms a Snowflake...

As photons rush in to illuminate the Snowflakes faultlessness they are temporarily lost in its beauty as they are bounced around the cold clear universe of miniature ice.

Once inside the Snowflakes temple walls the photons are hopelessly lost, some for an instant and others for an eternity… Either way the photon is humbled by the perfection of its Captor and even those that escape never revile the secrets nor would they miss the opportunity for reentry...

We witness from afar the brilliant dance of the Snowflake and the photon. Is it Chaos? Yes… But from our vantage point the Snowflake reveals its vibration to be only perfection, Pure and White…

Answer 2

It depends on how cold the freezer was.

A really cold freezer will freeze the water quickly trapping air bubbles in the water

A less cold freezer will allow the bubbles to be squeezed out during the freezing process.

Answer 3

Because sometimes oxegen gets trapped inside of the ice causing it to be impure causing it to be white. When this happens the air bubbles inside the ice are causing the ice to apear white when in acctuallity you are seeing the ice mirror the light as white. when it is clear it is a solid ice cube with no air trapped inside. if you look at rivers that froze over and then ponds you will notice that the pond will have air bubbles in it and the lake will not. this ive because the water running underneith keeps the air under it moving out making you be able to see under the ice. Isnt it wierd?

Answer 4

Because it doesn't absorb or reflect much electromagnetic radiation in the visible range.

Answer 5

air in the ice makes the ice opaque. no air in the ice makes the ice transparet

Answer 6

Because, when ice freezes it becomes a solid, and usually when liquids become solids it will turn a darker color then its normal color. Plus, ice isn't opaque its translucent.