The chemical triple representation has two aspects of meaning.According to external representation,it means the external expressions of the knowledge in macroscopic world,microscopic world and symbolic world.According to internal representation,it means the mental processing and presentations of these knowledge.The chemical triple representation is a whole and it is mutual connection,having important meaning in chemistry learning.

Based on the analysis of literatures,context in classroom teaching should be evaluated from two angles:structural characteristics and functional characteristics,and the evaluation criterion is constructed.Using the criterion,contexts in six excellent chemistry lessons are evaluated including some attributes and problems.