Analyze these tweo photomicrographs of ice crystals (snowflakes) by William Bent

Question

Analyze these tweo photomicrographs of ice crystals (snowflakes) by William Bentley (Fig. A3.2.5), I. Both ice erystals lave the same number of arms that radliate out from the center. How many arms do ice crystals have? 2. There are seven different crystal systems: triclinic monoclinic, orthorhombic, tetragonal, trigonal, hexagonal, and cubic. Using the number of arms on a snowflake as a hint, what crystal systein do ice crystals belong to? What is the basis for your interpretation? 0.1 mm 3. Which of the crystal forms shown in Fig. 3.5 or crystal habits shown in Fig. 3.6 do you recognize in the ice crystals? 4. Why do you think ice crystals do not all have the same shape? Figure A3.2.5 Analyze each crystalline household material pictured below (Figs. A3.2.6-A3.28). (Use a hand lens or microscope t observe actual samples of the materials if they are available.) Sucrose Figure A3.26 Figure A3.27 Figure A3.2.8 l, sucrose (table sugar) displays the following crystal forms..,amhfigas and as How can you tell? 3.6)_ epsom salt) displays the following crystal form(s) or habit (Figs. 3.5 and 3.6) or habit (Figs.3.5 the following crystal form(s) or habit (Figs. 3.5 and 3.6)

Explanation / Answer

I.1. The first picture in 3.2.5 is an example of the Dendrite type crystal and the second picture(bottom one) is an example of Sector type crystal.

Both of the crystals have 6 atoms of ice radiating out from the center.

I.2. As can be seen in the pictures, that the ice crystals are made up of six arms of water molecules radiating from the center. This six fold symmetry pattern defines the hexagonal symmetry of the ice crystals.

I.3. Both of the shapes/habits shown in the picture 3.2.5 are generally found in nature, but the Dendritic shape is more commonly found in natural ice.

I.4. Snowflakes, though seem to be very similar in shapes, can be of varied shapes. No two snowflakes can be totally identical to each other. Total 121 shapes of the snowflakes have yet been identified up to the elementary levels. This variability of shape is mainly due to the difference in the composing elements of the ice. The water molecules forming the snow crystals can be made up of one of the two isotopes of oxygen, further they can also vary on the type of hydrogen isotope they are made up of.

J.1. Sucrose fall in sphenoid class of the monoclinic crystal system. There are 3 symmetry axes in the sugar crystal, these are of unequal length, and one axis is perpendicular to the other two axes but the other axes are not mutually perpendicular. This arrangement of the axes define the monoclinic symmetry.

J.2. Epsom salt forms in the Monoclinic system, and the crystal form shown in the picture falls in the prismatic class(Habit) where there is only one two fold rotation axis perpendicular to the single mirror plane.

J.3. Halite falls in the isometric system, and the picture shown is of a cubic crystal habit.

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