1. Cov iav yog cov khoom tsis muaj tshuaj lom thiab tsis muaj tshuaj lom, uas txhais tau tias nws tsis tso cov tshuaj phem rau hauv cov ntsiab lus ntawm lub raj mis.
2. Cov iav yog cov khoom siv ruaj khov uas tuaj yeem tiv taus qhov kub thiab txias. Qhov no ua rau nws yog qhov kev xaiv zoo tshaj plaws rau khaws cov dej haus thiab lwm yam kua dej.
3. Cov iav tuaj yeem rov ua dua tshiab thiab tuaj yeem rov ua dua tshiab tsis tas yuav poob zoo. Qhov no txo qis cov khoom pov tseg hauv qhov chaw pov tseg thiab pab khaws cia cov peev txheej ntuj.
4. Cov iav yog cov khoom siv ntshiab uas tso cai rau kev pom yooj yim ntawm cov ntsiab lus ntawm lub raj mis. Qhov no yog qhov tseem ceeb tshwj xeeb rau cov khoom uas yuav tsum tau kuaj pom qhov muag, xws li tshuaj.
5. Cov iav yog impermeable, uas txhais tau hais tias nws tsis nqus tsw los yog tsw. Qhov no ua rau nws yog qhov kev xaiv zoo tshaj plaws rau khaws cov khoom noj thiab dej haus.
6. Cov iav yog ib qho yooj yim los ntxuav thiab ua kom huv, ua rau nws muaj kev xaiv nrov rau kev kho mob thiab chaw kuaj mob.
7. Cov iav yog cov khoom siv inert, txhais tau tias nws tsis hnov mob nrog lwm yam khoom. Qhov no ua rau nws yog qhov kev xaiv zoo tshaj plaws rau khaws cov kua dej uas nkag siab zoo rau ib puag ncig xws li oxygen, lub teeb, lossis kub.
