Solutions and Suspensions

Objective: To describe the unique properties of water and how these properties support life on Earth

How does water’s polarity influence its properties as a solvent? Water’s polarity gives it the ability to dissolve both ionic compounds and other polar molecules Watch the animation of a crystal of table salt dissolving in a glass of water Sodium and chloride ions on the surface of the salt crystal are attracted to the polar water molecule Ions break away from the crystal and gradually become dispersed in the water

How does water’s polarity influence its properties as a solvent? A solution is formed, which is one of two types of mixtures Mixture Solution Suspension Physical combination of two or more substances Mixture that has evenly distributed particles Mixture with non-dissolved particles

Water molecules sometimes split apart to form ions In pure water, this happens about 1 in 550 million water molecules H2O H+ + OH- Water hydrogen ion hydroxide ion More H+ forms acid in solution More OH- forms base in solution

Acids, Bases, and pH Chemists devised a measurement system called the _________ to indicate the concentration of H+ ions in solution pH scale

Why is it important for cells to buffer solutions against rapid changes in pH? The pH scale ranges from __________ A solution below a pH of 7 is __________ A solution above a pH of 7 is ___________ Pure water has a pH of ____ and is neutral Each movement from one number to the next increases or decreases the H+ ion concentration by 10 acidic basic 7

Why is it important for cells to buffer solutions against rapid changes in pH? The pH of fluids in most cells of the human body are between 6.5 and 7.5 If the pH is lower or higher, it will affect the chemical reactions that occur within the cells Controlling the pH is important for maintaining ___________, which is done through dissolved compounds called ________ homeostasis buffers