Are you sure you've heard the first consonant changing, not the last one? If we pronounce "как" separately, it's [kak]. But the sound of "к" changes to [g] when it is followed by a voiced consonant. For example, the next word starts with a voiced consonant. Как дела? [kagdilA] How are the things, how are you but Ну, как? (pause) Дела нормально? [nu,kak?(pause) dila narmAl'na?] So what's (new), are the things going ok? Later you will notice it happening with other consonants. Here is the list of unvoiced/voiced consonants and examples К-Г вокзал [vagzAl], к is followed by a voiced consonant з, so к becomes [g] Т-Д отдыхать [addyhat'], т is followed by д, so т becomes a voiced consonant too. Ф-В тариф за газ [tarivza gas] (Note: if you say things like that with pause, you will say [tarif (pause) za gas] Ш-Ж ваш день [vazh den'] С-З поезд [pOjest] П-Б укроп дикий [ukrObdIkij] Exception: letter В doesn't change the sound of the preceding letter. ЗдравстВуйте! [zdrAstvujte] (т stays т) швед [shvet] Also, these letters don't change the sound of the preceeding ones: Л,М,Н,Р

Brian, you are confusing something:/ But you know, speakers of different languages HEAR differently. Russian phonetics and English phonetics are different. Chinese phonetics is Very different. So it is possible that for Russians some sound is a clear K while for you it is a clear G:) It is a bit like.. for you Russia is "North", while for me Finland is "North" and mainland China is "South".

the standard is "k", nobody says it as "g"

"Как" is always pronounced with a [k] sound.

I can't imagine a Russian native pronounces "как" as [гак]. It's always [как]. Probably, you've heard the beginning of another word.