pH

Acids, Bases, and pH Water molecules can react to form ions. H2O --------- H+ + OH- (water) ---------- (hydrogen ion) (hydroxide ion) Water is neutral because the number of H+ is equal to the number of OH-.

pH Scale The pH scale indicates the concentration of H+ ions in a solution.

pH Acid- substance with a pH below 7 Base- substance with a pH above 7 The lower the number, the stronger the acid Base- substance with a pH above 7 The higher the number the stronger the base Neutral- pH around 7

Scale Each step on the pH scale represents a factor of 10. Buffers If something has a pH of 4, then there are 10 times the number of H+ as something with a pH of 5. Buffers Used to control pH levels for homeostasis Weak acids or bases that can react with strong acids or bases to prevent sharp, sudden changes in pH

Scientific Notation Giga G 1,000,000,000 1 x 109 Mega M 1,000,000 Prefix Abbreviation Factor of base unit Scientific Notation Giga G 1,000,000,000 1 x 109 Mega M 1,000,000 1 x 106 Nano n 0.000000001 1 x 10-9 Pico p 0.000000000001 1 x 10-12

Problem A child who measures one meter in height is 10,000 times larger than the typical animal cell. Which of these is the size of the animal cell in meters? A. 1 x 10-2 m B. 1 x 10-3 m C. 1 x 10-4 m D. 1 x 10-6 m

Solution The child who is one meter tall is bigger than the animal cell, therefore to find the size of the animal cell, divide 1 by 10000. To make 0.0001 a whole number, more the decimal point 4 places to the right. “4” will be the exponent for 10. Since the value (0.0001) is less than one, the exponent is negative. The correct answer is C.