Title and Source: Solid Water - http://www.elmhurst.edu/~chm/demos

Title and Source: Solid Water - http://www.elmhurst.edu/~chm/demos/
Two 400mL beakers
Table salt
Sodium polyacrylate – may be acquired from chemical supplier in pure form or may be
substituted with stuffing found in baby diapers
Food colouring
Stirring rod
Weighing cups/ trays
Weigh scale
Safety: consult sodium polyacrylate MSDS – do not allow ingestion of chemical or contact with
eyes, and avoid prolonged contact with skin. Sodium polyacrylate is slippery when wet – avoid
spills and ensure sufficient clean-up should they occur. Food colouring may stain surfaces,
clothing, or skin upon contact.
 Measure ~300mL water into one beaker – add a few drops food colouring
 Measure 5 – 7 grams sodium polyacrylate into second beaker
 Quickly pour water into second beaker with sodium polyacrylate – pour from height of
~12 inches to ensure vigorous mixing (stirring with rod after addition of water does not
achieve wanted results)
 What has happened to the mixture? (Turn beaker upside down to demonstrate)
 Measure ~10 grams table salt into weighing cup
 Pour salt onto the solid water and mix with stirring rod until becomes liquid again – more
table salt may be needed to acquire liquid consistency, add as needed
 Now, what has happened to the mixture? (Pour into other beaker to demonstrate)
 Liquid mixture – rinse down sink drain with plenty of water
 Solid mixture – dispose of in garbage
 Wash beakers and stirring rod with water (and soap if needed)
 Wipe down demo area with water and paper towel or cloth
 Wash hands with soap and water
What Will Happen: Quick, vigorous mixing of the water and sodium polyacrylate causes a
gelling of the water, making it into a “solid”. Addition of salt to the gel and stirring restores the
water to liquid form.
Why It Happens: Sodium polyacrylate is made of sodium ions surrounded by a polymer
membrane. When water is mixed with sodium polyacrylate, the area inside the polymer
membrane is more concentrated with ions than the area outside creating a concentration gradient.
Through the process of osmosis, water passes through the polymer from the area of low ion
concentration to area of high ion concentration. This movement of water into the polyacrylate
causes the compound “cells” to swell and form a gel of solid water. The addition of table salt
results in a reversal of the concentration gradient. Increasing the ion concentration outside the
polymer membrane to greater than the concentration inside causes the water to pass back through
the polymer, freeing it back into liquid form.
Bassam Z. Shakhashiri. (1989). CHEMICAL DEMONSTRATIONS: A Handbook for Teachers of
Chemistry. Volume 3: 368 – 371. The University of Wisconsin Press, 1930 Monroe
Street, 3rd Floor, Madison, Wisconsin 53704
Brooker, Robert J, et al. (2010). Biology, Canadian Edition. McGraw – Hill Ryerson Limited.
pg. 134 – 137.
Karp, Gerald. (2010). Cell and Molecular Biology: Concepts and Experiments. John Wiley &
Sons Inc. pg. 144 – 145.
Curriculum Fit:
Science 8 (SK) – Life Science: Cells, Tissues, Organs, and Systems (CS8.1)
 Analyze the characteristics of cells, and compare structural and functional characteristics
of plant and animal cells. [SI]
Biology 30 (SK) – Cell Structure and Function
1. Describe the structures and functions of cell components.
2. Explain how the processes of diffusion, active transport, photosynthesis, and respiration
are accomplished in a cell.
Wellness 10 (SK) – W11
 Make informed decisions regarding personal healthy eating practices based on
connections to wellness.
Grade 8 Science (AB) – Unit B: Cells and Systems
2. Investigate and describe the role of cells within living things
3. Interpret the healthy function of human body systems, and illustrate ways the body reacts
to internal and external stimuli
Grade 8 Science (MB) – Cluster 1: Cells and Systems (8-1-01)
 Use appropriate vocabulary related to their investigations of cells and systems. Include:
cell theory, osmosis, diffusion, selective permeability, unicellular, multicellular,
specialized cells and tissues, organs, systems, arteries, veins, capillaries, terms related to
cell structure, heart structure, components of blood, and primary and secondary defense
systems. GLO: C6, D1
Grade 8 Science (BC) – Life Science: Cells and Systems (B2)
 Relate the main features and properties of cells to their functions