Integrating Chemistry into SCI 210 The Dynamic Earth Andrea Koziol, Dept. of Geology

Chemistry in Earth science Chemical concepts actually quite pervasive Touched on in lecture in a number of instances

Emphasized in these areas Minerals Energy and mineral resources Greenhouse effect (action of CO 2 molecule) Chemical weathering H 2 O changes of state, latent heat (clouds and weather) Ozone in the stratosphere Numerical dating with radioactive isotopes

Crystalline nature Orderly internal arrangement of atoms in a lattice A specific pattern that repeats at regular intervals minerals

Oil and gas Oil and gas are hydrocarbons: chains or rings of C and H React with O 2 to form gas and heat energy For example: 2 C 8 H O 2 = 16 CO H 2 O + heat energy Natural resources

This is the Greenhouse Effect Water and CO 2 molecules absorb this heat energy The atmosphere is heated from the ground up This heat stays in the atmosphere Infrared H2OH2O CO 2 Greenhouse effect I

Chemical Weathering Chemical weathering: destruction or altering of minerals when rock comes in contact with water solutions or air. Examples: Dissolution by water or carbonic acid, oxidation, reaction to new minerals weathering

Chemical weathering examples Dissolution by carbonic acid: CO 2 dissolves in H 2 O (rain) to form weak carbonic acid (H 2 CO 3 ) which attacks limestone, marble weathering

Moisture and Clouds It’s about H 2 O and changes in state: Ice --- liquid --- water vapor Atmosphere II

Latent heat (hidden heat) Latent heat: heat added that is not associated with temperature changes. It is energy absorbed or released during a change in state. Storing this latent heat, moving it around, is important! Atmosphere II

Global: CO 2, Greenhouse Effect, Global Warming Today: CO 2 concentration in our atmosphere is >0.036 % or 360 PPM If less CO 2 : cooler temperatures and cooler climate If more CO 2 : warmer temperatures and warmer climate Global climate change

Most up-to-date info Global climate change

What is ozone? Oxygen molecule: O 2 Ozone molecule: O 3 Very little ozone in troposphere –What is there is a pollutant 90% of ozone is in the stratosphere Ozone

How this works, cont’d. O 3 + UV light energy = O 2 + O (UV light totally absorbed) O 2 + O recombine rather quickly Reaction repeats UV light from Sun almost totally absorbed Ozone

Parents and daughters Starting radioactive isotope: parent After decay, it’s different: daughter The number of protons, neutrons have changed by radioactive decay Example: carbon-14 (6 protons, 8 neutrons) decays to nitrogen-14 (7 protons, 7 neutrons) Numerical dating

Rate of decay How a parent atom decays, and rate of decay is fixed. Rate of decay doesn’t vary, no matter what physical or chemical conditions the isotope is in. Every parent atom produces one kind of daughter So: look at amount of parent left, amount of daughter present. Numerical dating

Now: radioactivity Radioactive decay is not linear. It is exponential. (see fig.10.14, decrease in # of parent isotopes as time passes) Numerical dating

Radioactive decay example Start with 160 parent atoms in our sample. How much time has passed? T = 0 half-l. 160 parents 0 dau. T = 1 half-l.80 parents80 dau. T = 2 half-l. 40 parents120 dau. T = 3 half-l. 20 parents140 dau. Look at ratio of parents to daughters to tell time. Numerical dating