1. The Nature of Matter

2. Matter  Anything that has mass and takes up space  Substance- single kind of matter that has a specific make-up and specific properties -Example: Salt or sugar -Non-Example: Muffin batter (the ingredients can vary) DESCRIBING MATTER (Notes 2-1)

3. Physical Properties of Matter  Can be observed without changing into another substance  Examples: Freezing point, melting point, density, texture, color, flexibility, solubility in water

4. Chemical Properties of Matter  Ability to change into a different substance  Examples: flammability, rusting, tarnishing, rising of bread in baking process

5. Elements  Pure substances that cannot be broken down into any other substance  Simplest substances  Is identified by its specific physical and chemical properties  Examples: Carbon, Oxygen, Gold, Silver, Aluminum

6. Atoms  Basic particle that makes up all elements  Having different atoms gives elements their unique properties  Atoms have a nucleus made up of positively charged protons and neutrally charged neutrons, and they are surrounded by a cloud of negatively charged electrons Modeling an Atom  Pencil “lead” is made of mostly graphite, a form of carbon. Two ways to model atoms used in this presentation are shown here for carbon.

7. Chemical Bonds and Molecules  Atoms bond, or combine, by chemical bonds (a force of attraction between the electrons of 2 or more atoms)  Often form molecules- groups of 2 or more atoms held together by chemical bonds Modeling Molecules  Examples: H 2 O, O 2, CO 2

8. Compounds  Pure substance made up of 2 or more elements chemically combined in a set ratio  Represented by a chemical formula which shows the elements in the compound and the ratio of atoms  When elements combine to form compounds, they have unique properties from those of the uncombined elements -Example: Hydrogen alone is a very combustible gas, Oxygen alone is a major supporter of combustibility, but when combined in the set 2:1 ratio H 2 O, they put out fires!

9. Mixtures  Made up of 2 or more substances that are not chemically combined  Examples: Air, Soil, Salt water  Differ from compounds because they do not have to have a set ratio, and each substance in mixture keeps its individual properties  Two Types, Heterogeneous and Homogeneous:  Hetero = different Can see different parts of mixture Examples: Soil, Salad  Homo = same * Can’t see different parts of mixture, evenly mixed * Examples: Sugar/water solution, Air

10. Separating Mixtures  Compounds are hard to separate  Mixtures are easy to separate since each component keeps its own properties  Look at figure 10 on page 66, it shows different ways to separate a mixture including using a magnet, filtering, distilling, and evaporating

11. Physical Changes  Alters form or appearance of matter but does NOT change matter into a different substance  Examples: -Changes of state (solid to liquid, or liquid to gas, etc.)-Changes in shape or form (dissolving, chopping, cutting, bending, breaking, etc) Changes in Matter (Notes 2-2) Chemical Changes A change in matter that produces one or more new substances Chemical change = chemical reaction New substances have properties different from original substances Examples:-burning of natural gas on gas stove (combustion)-rusting (oxidation)

12. Chemical Change

13. Law of Conservation of Matter  Matter is neither created nor destroyed in any physical or chemical change. No mass is lost because during a chemical change, atoms are not lost or gained, just rearranged. Conserving Matter: The idea of atoms explains the law of conservation of matter. For every molecule of methane that burns, two molecules of oxygen are used. The atoms are rearranged in the reaction, but they do not disappear.

14. ENERGY  Who remembers the definition of energy?  The ability to do WORK! Energy and Matter (Notes 2-3) All chemical and physical changes include a change in energy

15. Law of Conservation of Energy  Energy is neither created nor destroyed  It is only transformed (changed from one form to another)

16. Forms of Energy Four Forms of Energy that Include Changes in Matter  Thermal energy is related to temperature because the energy always flows from warm matter to cool matter Temperature = average energy of random motion of particles of matter Temperature = average energy of random motion of particles of matter Endothermic Change = energy is absorbed Endothermic Change = energy is absorbed Ex: Melting Exothermic Change = energy is released Exothermic Change = energy is released Ex: Combustion  Chemical energy is stored in chemical bonds between atoms. (Ex. Food, gas, cells)  Electromagnetic energy travels through space as waves. (Ex: Visible light, radiowaves, microwaves, x-rays, UV rays, infrared rays)  Electrical energy is the energy of electrically charged particles moving from one place to another. (Ex: electrons move from one atom to another in many chemical changes.)

17. Potential Vs Kinetic  Energy waiting to be used  Ex: Food you eat  Energy of Motion (Energy being used)  Ex: You taking notes!  Ex: You taking notes! POTENTIAL ENERGY: KINETIC ENERGY:

18. Transforming Energy Example 1:  Burning -Chemical change that transforms chemical energy and releases it as thermal energy (heat) and electromagnetic energy (light)

19. Transforming Energy Example 2:  Photosynthesis -Plants transform electromagnetic energy from the sun into chemical energy (sugar for plants)

20. Transforming Energy Example 3:  You Try!  What energy transformations occur when you ride a bike?  There is potential energy in the food you eat.  Your cells transform food into chemical energy your body can use.  Chemical energy is transformed to kinetic energy of moving muscles and thermal energy given off as heat.