Bellwork Fri. Aug. 28, 2015 Chloride ion Calcium ion Chloride ion Sea salt contains calcium chloride (CaCl2), an ionic compound similar to table salt. One atom of calcium (atomic number 20) bonds to two atoms of chlorine (atomic number 17). Fill in and draw the number of protons and electrons in each ion.   Chloride ion Calcium ion Chloride ion Protons ___ Protons Protons___ Electrons ___ Electrons Electrons ___ 2. What is the difference between an ionic bond and a covalent bond? Careful: look at the (-) and (++) 17 20 17 18 18 18 Ionic bonds: transfer of electrons from one atom to another Covalent bond: share electrons between atoms

2-2 Properties of Water

Properties of Water that make Life on Earth Possible……

Polarity: a water molecule is polar because there is an uneven distribution of electrons between oxygen and hydrogen atoms.

Hydrogen likes to give electrons away Oxygen is an “electron hog” – it tugs on electrons so that there is a higher density of electrons around the oxygen as compared to the hydrogen. And Hydrogen likes to give electrons away

2. Hydrogen Bonds Because of their partial positive and negative charges, polar molecules can attract each other.

3. Cohesion: an attraction between molecules of the same substance 3. Cohesion: an attraction between molecules of the same substance. Because of hydrogen bonding, water is extremely cohesive.

Adhesion: an attraction between molecules of different substances.

5. Ice floats in liquid water – water expands when it freezes and is less dense than its liquid form… good news for fish and all aquatic life!

6. High Specific Heat and has ability to remain a liquid over a large temperature range Why is this important? (Specific heat is just a fancy way of saying the amount of energy needed to raise the temperature of a substance) sooo… water heats up and cools down slowly…. And… since cells are mostly water – we don’t immediately boil in the desert

….or instantly freeze in the arctic!!

7. Water is the “Greatest Solvent on Earth” A. K. A 7. Water is the “Greatest Solvent on Earth” A.K.A. “the universal solvent” (dissolves stuff) due to its polar nature. - - Important to living organisms because many biochemical reactions take place only within aqueous (water is the solvent) solutions

A mixture is a material composed of two or more elements or compounds that are physically mixed together, but not chemically combined

Two types of mixtures can be made with water solutions and suspensions

Suspensions  Some materials do not dissolve when placed in water but separate into pieces so small that they do not settle out easily. Blood is about 55-60% water

Solution: components are evenly distributed throughout the solution Solution: components are evenly distributed throughout the solution. When a crystal of table salt is placed in warm water, sodium and chloride ions are attracted to the polar water molecules. When an ionic compound such as sodium chloride is placed in water, water molecules surround and separate the positive and negative ions.

salt in salt water. solute: the substance that is dissolved. Like the solvent: the substance in which the solute dissolves. Like the water in salt water.

Acids, Bases, and pH A water molecule is neutral, but can react to form hydrogen (H+) and hydroxide (OH-) ions. H2O   H+ + OH-

The pH scale  indicates the concentration or [ ] of H+ ions in solution. The pH scale ranges from 0 to 14.

The pH Scale At a pH of 7, the concentration [ ] of H+ ions = OH- ions, so the solution is Neutral The concentration of H+ ions determines whether solutions are acidic or basic.

Acids An acid is any compound that forms H+ ions in solution.  HCl = Hydrochloric acid – Stomach acid

Bases It is slippery to the Feel – like bleach A base is a compound that produces hydroxide ions (OH- ions) in solution.  It is slippery to the Feel – like bleach

Buffers: weak acids or bases that can react with strong acids/bases to prevent sudden changes in pH The pH of the fluids within most cells in the human body must generally be kept between 6.5 and 7.5. Controlling pH is important for maintaining homeostasis.

http://www.youtube.com/watch?v=0eNSnj4ZfZ8

The 2 chemical bonds in water: Bellwork: Wed. Sept. 3, 2014 The 2 chemical bonds in water: covalent bonds between the oxygen and the hydrogen atoms result from a sharing of the electrons. This is what holds the water molecules themselves together. hydrogen bond is the chemical bond between the water molecules that holds the mass of molecules together. A drop of falling water is a group of water molecules held together by the hydrogen bonds between the molecules.

2-2 Section Review Quiz A molecule in which the charges are unevenly distributed is called a polar molecule. cohesive molecule. hydrogen molecule. covalent molecule.

2-2 A dissolved substance is called a solvent. solution. solute. Suspension.

2-2 A compound that produces hydroxide ions in solution is called a(an) base. buffer. acid. salt.

2-2 Hydrogen bonds between water molecules result from adhesion between water molecules. magnetic attractions between water molecules. uneven electron distribution in each water molecule. ionic bonds in the water molecule.

2-2 On a pH scale, a value of 2 means that the solution has equal concentrations of H+ and OH- ions. the same concentration of H+ ions as pure water. higher concentration of H+ than in pure water. lower concentration of H+ than in pure water.

The END

Bellwork Tues. Sept. 2, 2014 Cl - - has _____electrons. 2. Magnesium has an atomic mass of?_______ and this one has ____electrons ______, _______ and _________ are the 3 most common elements in your body. What atom is this?_____________

5. The 4 most common elements in your body: 1 2 3 4