The scientist makes very methodical observations of the two different samples. He compares the weight. He comments that one of the samples feels different to him because it feels cold to the touch. He notices that there is a volume difference between the two because one has a different shape. He also addresses the idea of water and ice being the same fundamental thing because they both have water molecules. He also makes note of how freezing and melting change the form of matter, but not the material. When observing a particle of ice in a particle magnifier, the scientist notes that there is nothing to see between the identical particles. He notes that as the temperature increases the average speed of the particles also increases.
Students do not have the scientific vocabulary and knowledge to back up their observations. They are less certain of the words they want to use to describe their ideas and observations. They tend to look to others to confirm that what they are saying makes sense or sounds plausible.
In my classroom, there are usually one or two students who will share their thoughts and the other comments made are often the same ideas the first two students shared, but restated in a slightly different way.