Computational thinking (CT) is increasingly acknowledged as an essential skill to solve problems interdisciplinary. This paper describes the development and validation of the unplugged activity of CT in science (ACTS) module, which is specifically designed to integrate CT. The present study was conducted in five phases: Phase I was composed of needs analysis to elicit respondents' opinions regarding the knowledge of CT and appropriate topic to integrate CT within the year 5 science curriculum. Phase II was the development of the unplugged ACTS module, Phase III was content and face validation of the module, Phase IV was the implementation and Phase V was the evaluation of the effectiveness of the module. The needs assessment indicated that students have never known about CT. The module covered the "Matter" topic for year 5. A content validity index (CVI) was used to quantitatively assess content validity, finding a CVI of more than 0.79 as appropriate. The module was found to have a high mean of validity for content value (CVI=0.83). Expert members have made suggestions that will then be used to develop the module as required. This study concluded that the module has strong validity of the content and can be used to improve CT and science content knowledge among children in primary school.