asked in 科學及數學其他 - 科學 · 1 decade ago

About dry ice

1.Compare the cooling effect of dry ice and ordinary.

2.State FIVE applications of dry ice.

3.Dry ice must be handled with care.Why?And what should we do when handling dry ice?(Thanks and use English)

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  • Carson
    Lv 6
    1 decade ago
    Favorite Answer

    1.Compare the cooling effect of dry ice and ordinary.

    Dry Ice is frozen carbon dioxide, a normal part of our earth's atmosphere. It is the gas that we exhale during breathing and the gas that plants use in photosynthesis. It is also the same gas added to water to make soda water. Dry Ice is particularly useful for freezing, and keeping things frozen because of its very cold temperature: -109.3°F or -78.5°C. Dry Ice is widely used because it is simple to freeze and easy to handle using insulated gloves. Dry Ice changes directly from a solid to a gas -sublimating - in normal atmospheric conditions without going through a wet liquid stage.

    Ordinary ice only freeze at 0°C and melt at over 4°C which is very much higher than dry ice and ordinary ice changes from a solid to a liquid which will make things wet.

    2.State FIVE applications of dry ice.

    FOOD STORAGE

    Placing dry ice in the bottom of a dry food storage container is a very economical way to fumigate and store dry goods for an extended amount of time. As the dry ice sublimates it replaces the oxygen in the container with CO2. Leave the lid on but not tightly sealed until the dry ice completely sublimates. Then snap the lid tight. Without oxygen neither bugs nor bacteria can grow. This process is good for seeds, grains, legumes, flower, powdered milk, etc.

    DENTS & HAIL DAMAGE

    Dry ice will condense metal and thereby shrink small dents on your car.

    PROTECT SPORT FISH AND GAME

    Pack your trophy animal or fish in dry ice to minimize spoilage while transporting or shipping it home. Do not let the dry ice touch the game directly as it may cause superficial damage. Dry ice can be added to regular ice to extend its cooling. For best results use an insulated container.

    MEDICAL

    Doctors, to freeze skin for wart removal, use dry ice or liquid nitrogen. Many medical offices ship biological specimens in dry ice for laboratory testing or further processing. Dry ice is also used to keep bone morrow frozen when it is shipped.

    TRANSPORTING PLANTS

    Dry ice will keep flowers cool and delay blooming. Maintaining ready to flower plants at 1.11°C will retard blooming. Do not allow dry ice to get too close and freeze plants.

    CHEMICAL RETARDANT

    Its low temperature slows or stops some chemical reactions. It is used to store and ship special adhesives It is also a neutralizing agent for alkalis.

    PRESSURIZING AGENT

    When dry ice changes from a solid to a gas it absorbs heat and expands to over 800 times its original volume.

    INERTING MEDIUM

    Dry ice will replace oxygen in a container preventing or putting out fires. It is used to safely remove underground gas storage tanks.

    SHRINK FITTINGS

    Dry ice will shrink metal to slide on sleeves, bushings or bearings. Add Dry Ice to a 90% pure alcohol bath to create a cold liquid near -78.5°C. that can be used like liquid nitrogen.

    DEFLASHING MOLDED PLASTICS AND RUBBER

    Dry ice will cool and shrink whatever it touches. Rubber parts are tumbled in a barrel with dry ice, making them brittle for easy flash removal. It is used in cold grinding of PVC resins and vinyl's.

    3.Dry ice must be handled with care.Why?And what should we do when handling dry ice?

    Because of the extreme cold nature of dry ice, it has to be handle using tongs or insulated gloves or your body will suffer from cold damage(burnt by dry ice). Moreover, storing and transporting dry ice must be caution. NEVER PLACE dry ice into a closed container or the container will explode, as dry ice continuously sublimates as heat enters it from its surroundings. The CO2 gas that evolves must be vented from the container. Do not seal dry ice into a container, because an explosive bursting of the container can result. A styrofoam (polystyrene foam) ice chest with a loose fitting lid makes a good container for transporting dry ice.

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