化学
物质、原子与反应
你要讲的内容 · 先选年级
3 年级共 5 个知识点
Melting and FreezingHeating turns a solid into a liquid and cooling turns it back — and it's the same material the whole time.开讲 →Evaporation and CondensationWhere puddles go on a sunny day and why cold cups get wet — liquids turning to gas and back again.开讲 →Changes You Can UndoSome changes are reversible, like melting an ice cube, because you can get exactly what you started with.开讲 →Changes You Can't UndoBaking a cake or burning paper makes something new that can never be turned back — an irreversible change.开讲 →The Flow of HeatHeat always travels from warmer things to cooler things, which is why ice cream melts in your hand.开讲 →
往后的路 · 年级阶梯
Pick a grade · difficulty climbs 1 → 12
化学 across the grades
Grade 6Middle school
Atoms & elements · the periodic table, introduced