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According to the passage, solid carbon dioxide ----.
Carbon dioxide (CO2), like water and most other pure
substances, exists in solid, liquid, and gaseous states
and can undergo changes from one state to another.
Solid CO2, however, has an interesting property: at
normal pressures, it passes directly to the gaseous
state without first melting to the liquid state. This
property, together with the fact that this change
occurs at -78°C, makes solid CO2 useful for keeping
materials very cold. Because solid CO2 cools other
objects and does not leave a liquid residue, it is
called “dry ice”. As for liquid CO2, it is obtained by
putting carbon dioxide gas under pressure. When
liquid CO2 evaporates, it absorbs large quantities of
heat, cooling as low as -57°C. Because of this
property, it is often used as a refrigerant. If the
compressed gas from the evaporating CO2 liquid is
allowed to expand through a valve, the rapidly cooled
vapour forms solid carbon dioxide “snow”. This CO2
snow is compacted into blocks and is the source of
dry ice.