Chemical Changes and Balance in Living Systems

Vocabulary: Chlorophyll Photosynthesis Law of conservation of mass Cellular Respiration Law of Conservation of Energy Mechanical energy Chemical Reaction Trace Gases Atmosphere Glucose Oxygen Reactants Carbon Cycle

What is energy? In the study of physics, energy is defined as the capacity to do work. The Law of Conservation of energy states that energy cannot be created or destroyed, but will change from one form into another.

What is mechanical energy? Is the energy that is possessed by an object due to its motion or due to its position. It can be either kinetic energy (energy of motion) or potential energy (stored energy due to its position). Objects have mechanical energy if they are in motion and/or if they are at some position relative to a zero potential energy position or gravitational potential energy. Mechanical energy is the ability to do work. Any object that possesses mechanical energy-whether it is in the form of potential energy or kinetic energy. Examples of mechanical energy: In animals much of the energy from food is converted into motion. A baseball in motion.

Chemical Changes and Reactions: When atoms and molecules interact in a chemical reaction, chemical bonds break or new bonds form. Energy is stored in these chemical bonds, and this is why chemical reactions involve energy changes. Photosynthesis is an example of chemical process. Light energy joins water and carbon dioxide molecules to make glucose and oxygen. A chemical reaction can be described by a chemical equation. Photosynthesis indicates that 6 molecules of carbon dioxide react with 6 molecules of water. The reaction produces 1 molecule of glucose and 6 molecules of oxygen. Photosynthesis: LIGHT energy + 6CO2(CARBON DIOXIDE) + 6H2O(WATER) → C6H12O6 (GLUCOSE) → 6O2 (OXYGEN) The Law of Conservation of Mass states that during an ordinary chemical reaction, matter is not created or destroyed. A balance equation shows that the reaction does not create or lose any of the atoms that are part of the reaction. Instead all of the atoms are rearranged and recombined in different ways.

Photosynthesis: Is the process in which living things change light energy into chemical energy that it is stored in food. The organisms uses water from the soil and carbon dioxide from the air to make the food it needs. (SHOW VIDEO)

Parts of a plant that are important in the process of photosynthesis: Xylem- The stems of the plants that work like tubes to absorb water. They transport vital nutrients to the entire plant. Stomata- The pores of the leaf. They are responsible for the exchange of gases. Carbon dioxide enters the plan through the stomata and oxygen also comes out through the stomata. Mesophyll Cells- The first layer located under the epidermis but above the second layer, is the palisade parenchyma cells. This layer is inundated with loads of chloroplasts, making it the layer most directly responsible for photosynthesis. Chloroplast/Chlorophyll-Is a green chemical responsible for the green color of plants and it is able to capture energy. Once the CO2 & H2O enters the chloroplast in the presence of light the process of photosynthesis takes place. Glucose- Is a type of sugar that the organisms use as food. Organisms stores glucose in its cells for later use.

The Atmosphere: Mixture of gases that forms around the Earth The atmosphere is divided into layers accordingly to differences in temperature: troposphere (contains most of the mass in the atmosphere), stratosphere (contains the highest concentration of ozone layer, which job is to protect us from harmful radiation from the sun. It acts like a layer of sunscreen.), mesosphere, thermosphere, and exosphere. The atmosphere contains a mixture of nitrogen (78%), oxygen (21%), and Trace gases (Argon/Ar, Carbon Dioxide/CO2, and Ozone/O3 Carbon Dioxide- A gas that is produced when people and animals breathe out or when certain fuels are burned and that is used by plants for energy. It is released into the air as a waste product of cellular respiration. Plants also take CO2 from the air to perform photosynthesis. Carbon is part of every living organism, in the gasoline used by cars, and in many kinds of rocks. The Carbon Cycle: CO2 in the Atmosphere + Fossil/Fuels (Death & Decomposition)= Combustion (Coal & Oil form from the remains of animals and plants that died MYA.) Cellular Respiration: Glucose (Food/Carbohydrates ) and O2 = CO2 & H2O Photosynthesis: Carbon Dioxide + Water= Glucose & Oxygen

Cellular Respiration: Oxygen reacts with glucose to produce carbon dioxide and water, and release energy. The highest amount of energy comes from cellular respiration. Like all chemical reactions cellular respiration follows the law of conservation of mass. Reactants are the starting materials in a chemical reaction. Reactants undergo a chemical change in which chemical bonds are broken and new ones formed to make new products. A general reaction may be given by the equation: A + B → C In this example, A and B are the reactants and C is the product. In a decomposition reaction, such as: C → A + B C is the reactant, while A and B are the products. You can tell the reactants because they are at the tail of the arrow, which points toward the products H2 (hydrogen gas) and O2 (oxygen gas) are reactants in the reaction that forms liquid water: 2 H2(g) + O2(g) → 2 H2O(l). Notice mass is conserved in this equation. There are 4 atoms of hydrogen in both the reactant and product side of the equation and 2 atoms of oxygen. The state of matter (s = solid, l = liquid, g = gas, aq = aqueous) are stated following each chemical formula.

What relationship exists between photosynthesis and respiration? Photosynthesis and respiration are opposite processes. Photosynthesis uses carbon dioxide and water and produces oxygen and sugar. Respiration uses oxygen and sugar and gives off carbon dioxide and water.