Observing crystal of water

Question

By just freezing water and using an optical microscope, can I observe water crystals?

Or do I have to use a special light to see?

Answer 1

No special light is required, although you will want to keep the light source distant to avoid melting your ice. You will also want to experiment with light angles to get the best resolution of the different angled facets of the ice crystal.

Without the right equipment and experience it will be difficult to get an image quite as spectacular as the crystal you've shown. The keys to getting the best image are avoiding heat, from a lamp or the surrounding air, which causes sintering of the finest faceted crystals.

A good way to view ice under a microscope is to place crushed dry ice under a dark covering (depending on your equipment, getting something that fits and still focuses may be your greatest challenge). Whether you use glass or plastic or whatever else isn't very important. The dry ice is cold enough that ice will nucleate on the surface of your choice and grow from there. Be prepared to watch the whole show, from freezing to melting!

Answer 2

You can certainly "just freeze" some water and look at it - either through a microscope or directly. This type of frozen water will consist of one or, much more likely, many crystalline regions, but will have the shape of its container; what you have pictured is a single crystal of ice. In order to grow a single crystal, special methods must be used.

This link:http://www.its.caltech.edu/~atomic/snowcrystals/project/project.htm contains directions for making ice crystals at home but note the author incorrectly claims dry ice (solid CO₂) is "completely safe" but it is both capable of burning skin upon direct contact (especially if your skin is moist) and enough of it can kill if it sublimates (vaporizes) in a (very) small enclosed space. You must keep the concentration of $\ce{CO2}$ gas below the toxic limit, which is generally not a problem in an average size room. Use it only with gloves and adequate ventilation. To microscopically observe an ice crystal, you need a platform (or slide) to rest it on which has a temperature below freezing (otherwise it will melt). You also need a light source which is cool enough to avoid heating and melting the crystal. This is fairly easy outdoors when temperatures are below the middle 20s (°F) (-5 to -10°C). You should allow your microscope to slowly cool to ambient temperature or water may condense on the lenses and/or mirrors. Overnight in your garage, say, would be good (if your garage is unheated).

A snowflake, like the one you have pictured, is very difficult to make. They are formed in the atmosphere, and generally, you have no means of replicating that with common household items/equipment. There are a number of known chemicals which can be used to nucleate ice crystals, as well as some proteins and bacteria. The easiest way to create ice crystals is to cool a glass microscope slide (possibly with very small amounts of the nucleation materials on it) to well below 0°C and then expose it to humid air at about 2 - 5°C (35°-40°F). The water vapor will condense onto the slide. Don't allow the slide to warm up, however.