一
Water
Waterisveryimportantforlivingthings.Withoutwatertherecanbenolifeonearth.Allanimalsandplantsneedwater.Manalsoneedswater.
Waterisfoundatmosteverywhere.Eveninthedriestpartoftheworldthereissomewaterintheair.
Asweallhavefoundout,watermaybeasolid,oraliquidoragas.Whenitisasolid,itmaybeashardasbrick,Whenitisaliquid,youcanpouritoutofacontainer.Whenitisagas,youcannotseeorfeelit.
Althoughabout70percentoftheearth'ssurfaceiscoveredwithwater,therearemanyplacesintheworldstillrunningoutofwater.Soweshouldmakegooduseofwateronearth.
水
水对生物很重要,没有水,地球上就没有生命.所有的动植物都需要水.人类也需要水.
水几乎无处不在.即使在世界上最干燥的地方,空气中也有水.
水,正如你所了解的,有固态、液态和气态.当它是固态时,它可以像砖一样硬;当它是液态时,你可以将它从容器中倒出;当它是气态时,你看不见或感觉不到它.
虽然地球表面70%是水覆盖着,世界上仍有许多地方缺水.所以我们要好好利用地球上的水.
二
Waterisacommonchemicalsubstancethatisessentialforthesurvivalofallknownformsoflife.Intypicalusage,waterrefersonlytoitsliquidformorstate,butthesubstancealsohasasolidstate,ice,andagaseousstate,watervapororsteam.About1.460petatonnes(Pt)(1021kilograms)ofwatercovers71%oftheEarth'ssurface,mostlyinoceansandotherlargewaterbodies,with1.6%ofwaterbelowgroundinaquifersand0.001%intheairasvapor,clouds(formedofsolidandliquidwaterparticlessuspendedinair),andprecipitation.Saltwateroceanshold97%ofsurfacewater,glaciersandpolaricecaps2.4%,andotherlandsurfacewatersuchasrivers,lakesandponds0.6%.SomeoftheEarth'swateriscontainedwithinwatertowers,biologicalbodies,manufacturedproducts,andfoodstores.Otherwateristrappedinicecaps,glaciers,aquifers,orinlakes,sometimesprovidingfreshwaterforlifeonland.