It has been shown that science learning in school is difficult. Science is abstract and stuffed with laws, it has it's own language and it has not much in common with the learners lives. However, the nature of science implies that scientific language arisen from educated knowledge, can give word to unvoiced knowledge about science. This could be useful in school contexts to make children's silent knowledge become an incentive for science learning.PurposeThis study intended to depict school science learners' own knowledge and own expressions, i.e. emanating in their life-world, with expressions from the educated knowledge. The research questions are: Which physics knowledge is recognized in children's snowball fighting? and: What can primary school students snowball fighting tell about silent knowledge?MethodThe study involved thirty 11-year old primary school children from northern Sweden. Playing with snow is culturally embedded, hence an every day phenomena during winter. Snowball fighting was chosen with the purpose to analyze what children express when they think about and carries out this and if these expressions could be recognized as knowledge about physics.Data was collected from children's drawings and written explanations. Additionally, a video recording with a stimulated recall group interview was performed. The analysis was carried out step-by-step for each empirical resource and interpreted as life-world representations.ResultsAll children expressed their views both with drawings and in written explanations. One child explained: "You raise your arm backwards when you throw to get more force and what you should think about when you want to hit someone behind a shelter is to aim high". As expressed, with non-scientific as well as scientific words, it is possible to identify this child's silent knowledge within the explanation. Also, additional information about the children's silent knowledge was identified in children's discussions while watching a recording of a playful snowball fight. This knowledge, expressed in several and rich ways, can be recognized as knowledge about physics.ConclusionsPlayful activities, such as snowball fights, can be used to identify what silent knowledge children have. Following this, it is possible to identify what scientific words to add to existing knowledge and what science teaching needed to enrich children's learning about specific phenomena. The results suggest that teaching physics in primary school is facilitated if children's silent knowledge is understood.