Estimate the age of rocks in which the mole ratio of U-238 to Pb-205 is 0.75. The half life of U-238 is 4.5 x 10^9 yr. a) 3520 Yr b)4.89 *10^-18 s c) 2.8 *10^5 yr d)5.5 * 10^9 yr

What can be added to the examples section of each circle? endothermic: ice melting into water, and a heat pack becoming warm exothermic: a glow stick glowing, and fireworks exploding endothermic: ice melting into water, and an instant ice pack turning cold exothermic: fireworks exploding, and gasoline burning endothermic: a glow stick glowing, and a heat pack becoming warm exothermic: an instant ice pack turning cold, and ice melting into water endothermic: gasoline burning, and an instant ice pack turning cold exothermic: ice melting into water, and an instant ice pack turning cold

Which of these would be caused by a chemical change? a) the formation of lava. b) sedimantary rock layering over time. c) metamorphic rock forming from igneous. d) metamorphic rock eroding to form sedimentary rock.

Word equation for k+ h2o yield koh + h2