I’m reminded of my organic chemistry labs, where we watched the magic of titration. How the accumulation of one chemical (the titrant) elicited a colour-reaction from another (the indicator and analyte) but only when it reached that threshold of saturation—what we called the endpoint. Then, in an instant—in a single drop of the pipette— the colour changed. As though it were saying, “Enough! Enough!” and finally revealed its true colour.
Lumenlearning shows how much energy is needed to melt a kilogram of ice at 0ºC to produce a kilogram of water at 0°C. They demonstrated that a lot of energy is required and represents the same amount of energy needed to raise the temperature of 1 kg of liquid water from 0ºC to 79.8ºC.
We examine the effects of phase change more precisely by considering adding heat into a sample of ice at −20ºC (graph). The temperature of the ice rises linearly, absorbing heat at a constant rate of 0.50 cal/g⋅ºC until it reaches 0ºC. Once at this temperature, the ice begins to melt until all the ice has melted, absorbing 79.8 cal/g of heat. The temperature remains constant at 0ºC during this phase change. Once all the ice has melted, the temperature of the liquid water rises, absorbing heat at a new constant rate of 1.00 cal/g⋅ºC. At 100ºC.
Lumanlearning
Ice forms when the temperature lowers to zero degrees Centigrade. Liquid water expands, becomes less dense and more organized. In its solid state, water is crystalline, mineral-like, and floats over more dense liquid water. This is one of water’s many anomalous properties; most other liquids grow more dense in their solid states as molecules pack together tightly when the kinetic energy (temperature) decreases. The hydrogen bonds in water ice are strong, but their orientation causes molecules to push apart, lowering density, and forming a lattice or crystalline structure.
Nina Munteanu is a Canadian ecologist / limnologist and novelist. She is co-editor of Europa SF and currently teaches writing courses at George Brown College and the University of Toronto. Visit www.ninamunteanu.ca for the latest on her books. Nina’s bilingual “La natura dell’acqua / The Way of Water” was published by Mincione Edizioni in Rome. Her non-fiction book “Water Is…” by Pixl Press (Vancouver) was selected by Margaret Atwood in the New York Times ‘Year in Reading’ and was chosen as the 2017 Summer Read by Water Canada. Her novel “A Diary in the Age of Water” was released by Inanna Publications (Toronto) in June 2020.