What do you know about this equation? C 6 H 12 O 6 + 6O 2  6CO 2 + 6H 2 O What elements are present? How many of each are there? What compounds are involved? What is this an equation for?

THE NATURE OF MATTER 2-1

I. Atoms A. Greek for “unable to be cut” B. 100 million atoms in a row = 1 cm C. Made up of subatomic particles: 1. protons (+) 2. neutrons (no charge – neutral) 3. electrons (-)

II. Elements A. Substances made up of only one kind of atom 1. over 100 known elements 2. only about 20 found in living things 3. atomic # = number of protons (or electrons since they are equal) 4. The most abundant elements in living things are CHNOPS

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III. Chemical Compounds A. A substance formed by the chemical combination of two or more elements in definite proportions B. Examples : H 2 O, NaCl

C. Properties of the compound can be different than those of the element Example 1: H and O are gases but together they are liquid Example 2: Cl alone is a poisonous gas but with Na it creates harmless salt

IV. Chemical Bonds A. All atoms want to have 8 “valence electrons” in their outer shell in order to be happy. If they don’t they often bond with other atoms.

V. Ionic Bonding A. When one atom donates electrons to another. B. Some atoms like to lose electrons to make a shell of 8 and others like to gain them (usually happens between metals and non metals)

Ionic Bonds between Na and Cl

VI. Covalent Bonding A. Electrons are shared instead of lost or gained to form a molecule. B. Single bond - sharing a pair (2) electrons C. Double = sharing 2 pairs (4) electrons

VII. Hydrogen Bonds  Water molecules have very special properties that attract them to one another  These weak bonds (attraction) between water molecules are called Hydrogen bonds

Why Discuss WATER? All living things depend on it. Over 60% of the human body is water com/watch?v=nS ENolWbyYQ

VIII. The Water Molecule A. H 2 O = held together by covalent bonds B. Oxygen is bigger so the electrons are shared but unequally. Oxygen becomes slightly negative and hydrogen, slightly positive. C. This makes water a polar molecule (it has a slightly + and – side!)

Draw a picture in your notes of two water molecules interacting.  Label the charges on oxygen and hydrogen atoms, and label the hydrogen bond between the water molecules.

IX. Cohesion same 1. Cohesion – the attraction between molecules of the same substance Example: Water sticking to other water molecules! 2. Responsible for surface tension

3. Adhesion – attraction between molecules of different substances Example: Water sticking to a leaf X. Adhesion

4. Capillary Action- ability of a liquid (WATER) to flow in narrow spaces against gravity due to adhesion and cohesion. Example: water moving up roots/stems of plants!! Capillary Action XI. Adhesion and Cohesion play a role in Plants!

XII. Polar VS. Non-Polar Polar molecules are not attracted to non-polar molecules like oil

Do Now  What are the weak bonds that form between two or more water (H 2 O) molecules?

Today’s Objective  To observe the properties of water (cohesion and adhesion) in a Water Lab.  Water is vital for living things and cellular processes.  1. Go over lab procedure  2. Distribute supplies  3. Complete lab (Part 1) and answer questions  4. Clean up and review findings

Exit Card  What is the difference between adhesion and cohesion?  Can you name the steps of the water cycle?  How might cohesion play a role in the water cycle?