Change of State

These downloadable videos are part of the multimedia package Stuff and Substance, developed by the Gatsby Science Enhancement Programme (SEP). They can be used to introduce ideas of the energy changes which accompany changes of state.

Melting requires an energy input for the change from solid to liquid and so the temperature remains at a substance’s melting point during melting. Students find this difficult to accept – if something is being heated they expect the temperature to rise accordingly. In one video, a temperature-time graph grows simultaneously with a lump of lead heated from room temperature to above its melting point. Water requires a lot of energy to change from liquid to gas at its boiling point. Conversely, a lot of energy must be taken away to condense gaseous water. The second video shows the use of a Liebig condenser in a distillation apparatus. The thermometer position and the fact that water condenses at 10^o C are highlighted.

These video and animation files form part of the resources in the section Change of State in the Stuff and Substance multimedia package, which provides a series of interactive pages that can be used by teachers or students in the classroom.

Please note: From 2021, Adobe has discontinued support for Flash player and as a result some interactive files may no longer be playable. As an alternative method to accessing these files a group of volunteers passionate about the preservation of internet history have created project Ruffle (https://ruffle.rs/). Ruffle is an entirely open source project that you can download and run many interactive Flash resources. For further information regarding STEM Learning’s policy for website content, please visit our terms and conditions page.