1. Chemical Energy Fuel for Life

2. What is Chemical Energy? Chemical energyis the energy that is stored in the chemical composition of matter.Chemical energy is the energy that is stored in the chemical composition of matter. An example is the energy used by cells in your body come from the chemical energy in the food you eat.An example is the energy used by cells in your body come from the chemical energy in the food you eat. –Energy is released as the chemical compounds are broken apart.

3. What is a Chemical Element? chemical elementA chemical element is the simplest form of a substance. chemical element –If a chemical element is broken down it becomes protons, neutrons and electrons. Chemical elementsChemical elements make up all the things in the physical world around us. Chemical elementsChemical elements are listed in the Periodic Table of the Elements Chemical elements moleculescompoundsChemical elements combine to form molecules and compounds

5. What is a Chemical Compound? moleculeA molecule is two or more atoms of an element combined together. –Example: O 2, which is an oxygen molecule made from two atoms of oxygen. chemical compoundA chemical compound is the combination one or more elements. –Example: H 2 O, which is water made from two atoms of hydrogen and one atom of oxygen. –Chemical compounds –Chemical compounds can not easily be separated.

7. Mixtures and Solutions mixture not chemically combinedA mixture is the combination of substances that are not chemically combined. mixture –A mixture can easily be separated using physical means. –Example: Sand and iron mixture. solution solutionmixtureA solution is the combination of substances in liquid form. A solution is like a liquid mixture. –Solutions –Solutions are not chemically combined so they can easily be separated. –Example: Salt dissolved in water. SolutionsSolutions can be acidic, or basic, or neutral. This characteristic of solutions is called pH.

8. What is pH? pHpH stands for potential Hydrogen, and it measures the acidity of a solution. pH 0 to 14The pH of solutions are measured on a scale of 0 to 14 with 0 being the most acidic and 14 being the most basic. A value of 7 is considered neutral and is neither acidic or basic. pH –Examples: stomach acid = pH of 2.5 pH –Soda ash = pH of 11

9. pH Scale

10. What is a Physical Change? A physical change is a change in a substance where nothing new is created, (it does not change the chemical make up of the substance).A physical change is a change in a substance where nothing new is created, (it does not change the chemical make up of the substance). –Example: Ice melts to water (both are still H 2 O). –Physical changes are usually changes in phase, or state, of matter.

11. What is a Chemical Change? chemical changeA chemical change is a change that does create something new, (a new chemical make up results). –Example: When iron rusts. The iron (Fe) becomes iron-oxide (Fe 2 O 3 ). –Chemical changes –Chemical changes occur when elements recombine with other elements, or in different combinations. –Chemical changes –Chemical changes occur during chemical reactions.

12. Exothermic vs Endothermic Chemical reactions exothermic endothermicChemical reactions often involve heat and can be either exothermic or endothermic. Exothermicchemical reactions give off heat. (feel hot)Exothermic chemical reactions give off heat. (feel hot) Endothermicchemical reactions take in heat. (feel cool)Endothermic chemical reactions take in heat. (feel cool)