Vaisesika Sūtra 5.2.08

अपां संघातो विलयनं च तेजः संयोगात् ॥८॥

apāṁ saṅghātō vilayanaṁ ca tējaḥ saṁyōgāt ॥8॥

[अपाम्-संघातः (apām-saṅghātaḥ) - freezing of waters; विलयनं-च (vilayanam-ca) - and melting; तेजः-संयोगात् (tejaḥ-saṁyogāt) - from conjunction with heat;]

The freezing and melting of water arise from conjunction with heat.