This reaction is vigorous and highly exothermic and the hydrogen resulted may ignite in air or even explode in the case of Rb and Cs.
ðɪs ɹɪˈækʃən ɪz vˈɪɡɚɹəs ænd hˈaɪli ɛɡzəðˈɜːmɪk ænd ðə hˈaɪdɹədʒən ɹɪzˈʌltᵻd mˈeɪ ɪɡnˈaɪt ɪn ˈɛɹ ɔːɹ ˈiːvən ɛksplˈoʊd ɪnðə kˈeɪs ʌv ˌɑːɹbˈiː ænd sˌiːˈɛs.