Describing Matter - PowerPoint PPT Presentation

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Describing Matter

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  1. Describing Matter The mass of an object is a measure of the amount of matter the object contains. The volume of an object is a measure of the space occupied by an object.

  2. Identifying Substances Matter that has a uniform and definite composition is called a substance. A physical property can be observed or measure without changing a substance’s composition.

  3. Identifying Substances

  4. States of Matter A solid is matter that has a definite shape and volume.

  5. States of Matter A liquid is matter that has an indefinite shape and has a fixed volume.

  6. States of Matter A gas is matter that takes both the shape and volume of its container.

  7. Physical Changes During a physical change, some properties of a material change, but the composition does not change.

  8. Classifying Mixtures A mixture is a physical blend of two or more components.

  9. Classifying Mixtures A homogeneous mixture is a mixture with a uniform composition. A heterogeneous mixture is a mixture with a variable composition.

  10. Separating Mixtures The process that separates a solid from a liquid in a heterogeneous mixture is called filtration.

  11. Separating Mixtures During a distillation, a liquid is boiled to produce a vapor, which is then condensed into a liquid.

  12. Elements and Compounds An element is the simplest form of matter that has unique properties.

  13. Elements and Compounds A compound is a substance that contains two or more elements.

  14. Chemical Changes A chemical change produces matter with a different composition than the original matter.

  15. Chemical Changes The ability of a substance to undergo a specific chemical change is called a chemical property. One or more substances change into one or more new substances during a chemical reaction. A substance present at the start of the reaction is a reactant. A substance produced in the reaction is a product.

  16. Recognizing Chemical Changes A precipitate is a solid that forms and settles out of a liquid mixture.

  17. Recognizing Chemical Changes The law of conservation of mass states that in any physical change or chemical reaction, mass is conserved.

  18. Energy Energy is the capacity for doing work or producing heat. In the SI system of units, the joule (J) is used to measure energy. The calorie (cal)is another unit that is used to measure energy.

  19. Energy To convert between joules and calories, the following equivalence statement is used: 1 cal = 4.184 J In chemistry, our main energy focus is going to be heat energy, or heat.

  20. Energy Transformations Heat, represented by q, is energy that transfers from one object to another because of a temperature difference between them. heat Heat always flows from a warmer object to a cooler object.

  21. Energy Transformations Temperature is a measure of the average kinetic energy of particles in matter.

  22. Exothermic and Endothermic Processes In studying energy changes, you can define a system as the part of the universe on which you focus your attention. The law of conservation of energy states that in any chemical or physical process, energy is neither created nor destroyed. The surroundings include everything else in the universe.

  23. Exothermic and Endothermic Processes An endothermic process is one that absorbs heat from the surroundings. In an endothermic process, the system gains heat as the surroundings cool down.

  24. Exothermic and Endothermic Processes An exothermic process is one that releases heat to its surroundings. In an exothermic process, the system loses heat as the surroundings heat up.

  25. Heat Capacity and Specific Heat The amount of heat needed to increase the temperature of an object exactly 1°C is the heat capacity of that object. • The specific heat capacity, or specific heat, of a substance is the amount of heat it takes to raise the temperature of 1 g of the substance by 1°C.

  26. Calorimetry Calorimetry is the precise measurement of the heat flow into or out of a system for chemical and physical processes.

  27. Calorimetry Calculations can be made from calorimetry data using the following equation: q = m x c x T where m is mass, c is the specific heat of water, and T is the change in temperature