1. Biology 2 Chapter 3

2. Polar Molecule Water molecules are shaped something like a wide V with opposite ends of the molecule having opposite charges

3. Cohesion When the hydrogen bonds hold a substance together

4. Adhesion The clinging of one substance to another

5. Surface Tension A measure of how difficult it is to stretch or break the surface of a liquid.

6. Kinetic Energy The energy of motion

7. Heat A measure of the total amount of kinetic energy due to molecular motion in a body of matter How fast the molecules in an object move

8. Temperature Measures the intensity of heat due to the average kinetic energy of the molecules

9. Celsius scale The temperature scale most often used in science 0 degrees Celsius is freezing, 100 degrees Celsius is boiling

10. calorie The amount of heat it takes to raise the temperature of 1 g of water by 1 degree Celsius

11. Kilocalorie 1,000 calories, the quantity required to raise the temperature of 1 kilogram of water by 1 degree Celsius 1 kilocalorie = 4184 joules

12. Specific heat The amount of heat that must be absorbed or lost for 1 g of that substance to change its temperature by 1 degree Celsius High specific heatLow specific heat

13. Heat of Vaporization The quantity of heat a liquid must absorb for 1 g of it to be converted to the gaseous state Water has a high heat of vaporization compared to other liquids To evaporate 1 g of water at 25 degrees Celsius about 580 cal of heat is needed

14. Evaporative Cooling Occurs because the “hottest” molecules, those which have absorbed the greatest amount of kinetic energy are the most likely to leave a gas

15. Solution A liquid that is a completely homogeneous mixture of two or more substances

16. Solute and Solvent Solvent is the dissolving substance and the substance that is dissolved is the solute

17. Aqueous Solution A solution in which water is the solvent

18. Hydration Shell The sphere of water molecules around each dissolved ion

19. Hydrophilic Any substance that has an affinity for water Hydro = water, philic = loving Like cotton and other forms of cellulose

20. Colloid A stable suspension of fine particles in a liquid

21. Hydrophobic Substances that are nonionic and nonpolar which actually seem to repel water E.g.- oil

22. Molecular Mass The sum of the masses of all the atoms in a molecule

23. Mole 6.02 x 10 to the 23 rd power Avogadro’s number The molecular mass in grams is a mole

24. Molarity The number of moles of solute per liter of solution The unit of concentration most often used by biologists for aqueous solutions

25. Hydrogen Ion H+, a single proton with a charge of 1+

26. Hydroxide Ion OH-, has a charge of 1-

27. Acid A substance that increases the hydrogen ion concentration of a solution

28. Base A substance that reduces the hydrogen ion concentration of a solution

29. pH A scale which measures the acidity or alkalinity of a substance The lower the pH the more acidic a substance is The higher the pH the more basic a substance is Note that each decrease in pH by one pH unit means a tenfold increase in the concentration of hydrogen ions.

30. Buffers Substances that minimize changes in the concentrations of H+ and OH- in a solutions

31. Acid precipitation Refers to rain, snow or fog with a pH lower or more acidic than pH 5.6