While there has been a remarkable worldwide convergence in the emphases of primary science curricula over the last four decades, the cognitive and knowledge demands that they make on learners have not been well-researched. Without knowing what these intellectual or epistemic requirements are when learning science in school, issues concerning curricular alignment and access to abstract disciplinary knowledge are also likely to occur. To highlight the value of such forms of analyses, we examine the intended primary science curricula from Korea and Singapore using revised Bloom's taxonomy, as well as describe some of their general features for teaching. The results contribute insights into the complexities of the science curriculum among two similar yet different educational systems that have performed well in international science achievement tests at primary levels.