This reaction becomes more vigorous going down the group: lithium reacts steadily with effervescence, but sodium and potassium can ignite, and rubidium and caesium sink in water and generate hydrogen gas so rapidly that shock waves form in the water that may shatter glass containers.
ðɪs ɹɪˈækʃən bɪkˌʌmz mˈoːɹ vˈɪɡɚɹəs ɡˌoʊɪŋ dˌaʊn ðə ɡɹˈuːp: lˈɪθiəm ɹɪˈækts stˈɛdili wɪð ˌɛfɚvˈɛsəns, bˌʌt sˈoʊdiəm ænd pətˈæsiəm kæn ɪɡnˈaɪt, ænd ɹuːbˈɪdiəm ænd sˈiːsiəm sˈɪŋk ɪn wˈɔːɾɚ ænd dʒˈɛnɚɹˌeɪt hˈaɪdɹədʒən ɡˈæs sˌoʊ ɹˈæpɪdli ðæt ʃˈɑːk wˈeɪvz fˈɔːɹm ɪnðə wˈɔːɾɚ ðæt mˈeɪ ʃˈæɾɚ ɡlˈæs kəntˈeɪnɚz.