Law of Conservation of Energy Photo by Peter Murray-Rust Heat and the Law of Conservation of Energy

How do you measure the kinetic energy of atoms and molecules? Remember, in chemistry we will mainly be focusing on the internal energy of objects. This means we will study the kinetic and potential energies of the atoms, ions, and molecules that make up matter. How do you measure the kinetic energy of atoms and molecules? You measure the temperature !

Temperature measures the average kinetic energy of the particles in a system. The higher the temperature, the faster the particles are moving. We measure temperature in either the Celsius or Kelvin scales. 0oC = 273 K Kelvin = oC + 273

What part of a compound stores potential energy? It takes energy to make chemical bonds, and the energy used to make them is stored inside of these chemical bonds. The potential energy stored in bonds between atoms and ions is called chemical energy. Methane

Transmitting Heat THROUGH Objects Heat passes through solids by the process of ___________. This happens when the particles in the solid bump into each other and pass the energy. conduction

Transmitting Heat THROUGH Objects Fluids, which are liquids and gases, are able to pass heat through the process of __________ because they can _____. convection flow Diagram by Eyrian

Transferring Heat BETWEEN Objects Whenever heat is passed between two objects that are touching, the heat is primarily transferred through the process of ____________. conduction It does NOT matter if the materials are solids, liquids or gases. When they bump into each other, they pass heat through the process of conduction. Heat travels from the metal pot to the water, and from the water to the noodles through the process of conduction. Photo by Antoinel

Transferring Heat BETWEEN Objects Whenever heat is passed between two objects that are NOT touching, the heat is transferred through the process of _________. radiation

Image by Lcamtuf Radiation is the transfer of heat through electromagnetic waves. Everything emits radiation; it is just not always visible to the naked eye. The hotter the object, the more radiation it emits. Image by Arno / Coen Image by Arno / Coen

Law of Conservation of Energy The Law of Conservation of Energy states that the total energy of a closed system remains constant. This can also be stated as Energy is not created or destroyed. While conceptually this is similar to the law of conservation of mass, it is sometimes harder to grasp since there are many energy conversions where energy changes its form as it is transferred.

When a chemical reaction takes place, energy is either absorbed or released. This is because chemical bonds require energy to be formed, and when they are broken, energy is released. This energy is most often absorbed and released in the form of heat and light.

In the cells of your body, the main energy molecule is adenosine triphosphate (ATP). Energy is absorbed by the ATP in the form of heat when a chemical bond is created. At this point, the energy is stored inside of the bond in the form of chemical energy until it is needed by the cell. Energy is released from the molecule in the form of heat when the bond is broken. A

Law of Conservation of Energy When you are verifying the law of conservation of mass, you just have to count grams, and this is not hard to do. To verify the conservation of energy, you have to count the amount of joules of radiant energy, kinetic energy, chemical energy, etc. before and after a reaction. Students also tend to think of heat, light and motion, and chemical bonds as very different things, but they are all forms of energy, and they affect one another.

Law of Conservation of Energy The important thing for you to remember is that if it appears energy was lost, then it must have left in the form of heat. Likewise, if it appears energy was gained, then it was absorbed from its surroundings in the form of heat. We will spend the next 2 classes learning and practicing how to calculate the heat that would be gained or lost during a chemical reaction.

Important Vocabulary If a chemical reaction absorbs energy from its surroundings, then we call it an endothermic reaction. Energy is absorbed during chemical reactions to make more chemical bonds. This means that the products have more stored chemical energy than the reactants.

Important Vocabulary H2 + Cl2 + HEAT 2HCl If a chemical reaction absorbs energy from its surroundings, then we call it an endothermic reaction. H2 + Cl2 + HEAT 2HCl Because heat is absorbed by the reaction, heat appears on the reactant side of an endothermic chemical equation.

Important Vocabulary If a chemical reaction releases energy to its surroundings, then we call it an exothermic reaction. Energy is released during chemical reactions when more bonds are broken than made. This means that the products have less chemical bonds and less stored energy than the reactants.

Important Vocabulary 2H2 + O2 2H2O + HEAT If a chemical reaction releases energy to its surroundings, then we call it an exothermic reaction. 2H2 + O2 2H2O + HEAT Because heat is released by the reaction, heat appears on the product side of an exothermic chemical equation.