Solutions and Properties of Water

Do Now Is chlorine a reactive element? Explain why or why not.

Go Over Assignment Practice problems #2, 3, & 9 (p. 14) 1.2 Questions: Pg. 23-24 #1-5 Diagrams of Atoms Summative Assignment–Due Monday, February 8th.

The Plan Learn about chemical change, solutions, solvents & solutes. Discuss why water is an excellent solvent. I can explain how dissolving substances in water is often required for chemical reactions.

Chemical Change The way to tell if a chemical change is occurring or has occurred is if there is a new substance produced, accompanied by a change in colour, odour, state, or energy. Changes in state usually involve formation of gas or solid.

Chemical Change Chemical changes show that bonds between atoms in the original substance have been broken and new bonds have been formed to create new substances. Weird Chem RXN

Solutions Often, substances are dissolved in water in order for chemical changes and reactions to occur. When matter is dissolved in water this forms something called an aqueous solution. Examples: Sea water, urine, crystal light

Alka Seltzer in Stomach Reaction NaHCO3 + HCl => NaCl + CO2 + H20

Solutions Solutions are homogeneous mixtures of substances composed of at least one solvent and one solute Solvents are the substances in which the solutes dissolve. Water is the most common solvent and forms aqueous solutions. Solutes are the substances dissolving into the solute. (e.g. in salt water, salt is the solute and water is the solvent.)

Crystal Light What is our solvent? What is our solute?

Structure of Water Triatomic molecule Held together by covalent bonds Meaning it has 3 atoms Held together by covalent bonds Oxygen and the 2 hydrogens share the electrons

Structure of Water Oxygen has a stronger pull on the electron than hydrogen. it is considered to be a polar molecule, because one end (the oxygen) has a more negative charge than the other end (the hydrogen). Polarity DEMO

Polarity of Water polar molecules attract one another  water molecules tend to “stick together” more strongly than other molecular compounds that are non-polar polar substances act as good solutes for other polar molecules and for all ionic compounds.

Aqueous Solutions Aqueous solutions are by far the most common and versatile type of solutions All aqueous solutions are clear or transparent

Solvation The process of a solute dissolving in a solvent Solute is added to solvent  solvent particles attract solute particles  bonds holding solute together break down  solute becomes surrounded by solvent molecules if the attraction between particles of the solute is stronger than those with water, the particles of the solute will not solvate very much (e.g. oil in water)

Assignment Read pgs. 24-31 1.3 Questions pg. 33 #1,2,4, 5