Chapter 2 Chemistry

It is important to know the chemistry that is involved in the cycling of nutrients, resource use, and pollution. Some of our chemicals are naturally occurring and some anthropogenic (manmade)

The Chemistry of Carbon, Nitrogen, Oxygen, Phosphorus, & Sulfur Carbon= Backbone of all organic compounds including all of the important molecules found in living organisms Fossil Fuels and Carbon dioxide (important green house gas)

Nitrogen= Most abundant element in the earth’s atmosphere at 78 %. Found in the amino group of every amino acid, the building block of protein Nitrogen runoff from agricultural land is an important contributor to nutrient pollution in waterways. Nitrous oxide is an important greenhouse gas

Oxygen= The second most abundant element in the atmosphere at 21 % Most abundant element in the earth’s crust Oxygen was added later into the atmosphere through photosynthesis of green plants Necessary for cellular respiration

Phosphorus= Component of nucleic acids and phospholipids Sulfur is a major constituent of volcanic eruptions and a contaminant of coal that contributes to acid rain

Defining Matter Matter is anything that has mass Found in 2 chemical forms elements & compounds Matter Quality= is a measure of how useful a form of matter is to humans as a resource based on its availability.

High Quality Matter= easier to extract and is concentrated High Quality Matter= easier to extract and is concentrated. Found near earth’s surface & has greater potential for use Low Quality matter=located deep underground or dispersed in ocean or atmosphere. Has little potential for use.

Physical & Chemical Changes Physical change is when the chemical composition does not change. (Solid ice melting into liquid) Chemical change is when rearrangement of atoms occurs and get a different product (Chemical reaction) Coal + Oxygen = Carbon dioxide + energy With chemical reactions energy is released

Law of Conservation of Matter When a physical or chemical change occurs, no atoms are created or destroyed There is no “away” in to throw “away” Everything remains with us in some form We can remove harmful substances but cannot get rid of it

Types of Pollutants We can always produce some pollutants but we can always produce much less and clean up. Persistence is the measure of how long the pollutant stays in the air, water, soil, or body 4 Categories

Degradable= broken down completely Biodegradable= Living organisms break down Slowly Degradable= takes decades to degrade Example includes insecticide DDT and most plastics Nondegradable= Cannot be broken down Examples include mercury, lead, arsenic Law of Conservation of Matter means we will always face the problem of what to do with some quantity of wastes and pollutants

Experimental Design Most common type of experiment= controlled experiment Don’t forget the control! Write a testable hypothesis (If… then…..because) Isolate one variable to measure and one variable to manipulate

Experimental Design Independent Variable is manipulated during the experiment Dependent Variable is measured during the experiment Example: Design an experiment to determine how soil pollution affects elderberry bushes. 1. Select two variables, one you can manipulate and one you can measure

Experimental Design Manipulate the concentration of a pollutant (salt) Pick something you measure (the number of elderberries produced by each bush) Hypothesis: Increased salt concentration in soil result in a decrease in the number of berries

Experimental Design Don’t forget the control! Collect and analyze data Draw Conclusions

FRQ Practice Unit #1- APES- FRQ For thousands of years, clams have been dug up along the beaches of California for food, first by Native Americans, and these days often by tourists. Today, the clam population is at an all-time low, and many scientists agree that several species of clams will inevitably become extinct in California. Dr. Kim, a marine biologist, believes that DDT dumped into the ocean during the 1950’s and 60’s could be another factor in the dramatic decrease in the clam population.

Write an argument to explain why the decline in the clam population could be considered an example of a tragedy of the commons. Identify and describe two strategies that could be employed to prevent any decline in the clam population due to a tragedy of the commons. Design a controlled experiment to support or refute the claim by Dr. Kim that DDT is playing a role in the clam’s demise. Include a detailed description of the experiment that includes the hypothesis being tested, a description of the data being collected, and identification of the dependent and independent variables in the experiment.

Environmental Systems A set of interacting components connected in such a way that a change in one part of the system affects one or more parts other parts of the system Examples of systems include the human body, populations, river, or the entire earth

Open Vs Closed Systems Most systems are open, where matter and energy exchanges occur across boundaries. Examples: the ocean receives energy from the sun which is transferred to plants and algae. Energy and matter are transferred back to the atmosphere from the ocean. Earth is a closed system due to its gravitational field. Little matter enters or leaves it. Calculating inputs and outputs tell us about systems. When they are equalsteady state

Feedback:- refers to responses made after change has been detected Positive feedback mechanism: reinforces (enhances) the original trend (change) Negative feedback mechanism: damps out an existing trend (change) Example of a positive feedback mechanism: warming, evaporation, water vapor, warming

Anthropogenic Changes Changes in the environment caused by people Ex: Diverting water away from Mono lake Damming Rivers Cities encroaching on wild areas Human activities have increased the pace and the intensity of environmental changes Natural systems do evolve over time but at a much slower rate.