2. Remember This?

3. Keeping the Roads Open
De-icing  - removal of existing, snow ice, frost, etc., from a surface.
Mechanical (ploughing or scraping) or
Chemical (application of salt or other ice melting chemicals)
Anti-icing  - pretreatment of a road, pavement etc with ice melting chemicals before it snows/freezes, to prevent or delay the formation of ice, or the adhesion of ice and snow.

4. How does it work?
When the temperature of water is lowered, the molecules will lose energy and hence come closer together to try to form the hydrogen bonding required for ice. If impurities (salt) are in the way, they need to lose more energy to create the bonding. Hence the lower freezing point

5. How does it work?
Freezing point is a colligative property – it depends on the number of particles, not their type or mass. At low concentrations the relationship is proportional.

6. Cost
To keep the Forth Road Bridge open costs between £34,000 and £104,000 per annum – just for materials! Aberdeenshire council use an average of 25,000 tonnes of salt per year – costing getting on for a million pounds!

7. What to use? • Chloride based • Acetate based • Formate based
• Glycol based
• Other Additives

8. What are the Problems?
Cost
Corrosion
Environmental Impact