<p>The work presented in the poster is focused on the analysis of different sand samples in laboratory activities, at the level of middle school Portuguese science education. The role of practical work in offering students the opportunity to experience the process of scientific investigation is one of the arguments for practical work in science education. Students are expected to both learn scientific knowledge and mobilize science process skills whenever they are doing practical activities. Practical work has an important role in helping students to develop links between observations and ideas and to develop students&#8217; understanding of science processes.</p><p>In sand analysis lab activity the students studied different sand samples under magnification and made observations on the sand grains size, sorting, shape, and composition. The differences in sand samples were related by the students to the depositional environments. For instance, the average size of the sand particles reflects both the strength of the current that carried them and the sizes of the crystals eroded from the parent rock. The range and relative abundance of the various sizes are also significant. The shapes of sand grains can also be important clues to their origin. Sand grains are rounded by abrasion as grains are knocked together during transport. For that reason, angular grains usually imply short distances of transportation. From the composition of sands, it is also possible to deduce the nature of the source areas that were eroded to produce the sand grains. The poster gives some examples of the observations of sand samples, in order to make clear the procedures and the discussion followed in the classroom.</p><p>The activity presented also intended to promote the development of science process skills with different levels of complexity. The science process skills are considered to be ways of thinking more directly involved in scientific research, such as observing, measuring, predicting, formulating problems and hypotheses, controlling variables and, interpreting data. These aspects are discussed in the poster and some examples of science process skills are given.</p>