Year 5 were given a variety of objects made from different materials, and sorted them according to how hard or soft these objects were.  They then tested their ideas using a nail to scratch the objects, and made a second judgement based on how easy it was to scratch the object.  Lastly, we tested the trustworthiness of our investigation by comparing our results.  We were surprised that our results were so different, and concluded that the method of observation was not as reliable as we had first thought!