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Introduction to Chemistry Matter and Change

Explore the study of matter, its properties, and the changes it undergoes. Learn about the different fields of chemistry, how to study chemistry, and the scientific method. Discover the characteristics of states of matter, how to describe matter, and the properties of matter.

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Introduction to Chemistry Matter and Change

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  1. Introduction to ChemistryMatter and Change Chapters 1 & 2

  2. What is Chemistry? • The study of matter, its properties and the changes it underdoes What is Matter? • Anything that has mass and takes up space

  3. What is Mass? • The amount of matter an object contains What is Volume? • The amount of space occupied by matter

  4. Why Study Chemistry? • Helps us better understand nature • Helps us understand how things work (cleaning products, pharmaceuticals, shampoos, biology) • Can improve quality of life (plastics, permanent press, recycling processes, medical treatments) • Develops critical thinking skills, analytical skills, skills to organize and manage information

  5. Fields of Chemistry • Organic • Analytical • Physical • Inorganic • Polymer • Medicinal • Environmental • Biochemistry

  6. How We Study Chemistry • Collect data (observations, measurements) • Analyze data (tables, graphs, calculations) • Interpret & Explain data • Draw conclusions • Evaluate data • Design new experiments • Understand and evaluate what others have done • Develop models and theories • Identify laws

  7. Scientific Method • Questions/Observations • Hypothesis • Design Experiment • Collect Data • Analyze Data • Revise Hypothesis

  8. Variables • Independent Variable (IV) • Experimenter changes purposefully • When graphing – x-axis • Dependent Variable (DV) • The variable that is measured based on the change in the IV • When graphing – y-axis

  9. Identify the IV and the DV • Cut paper towel into strips • Fill a container with water. • Place the strip into the water for a specified time interval (10, 20, 30, 40 sec) • At the end of the time interval mark the water level with a pencil

  10. Experimental Design - Trials • Trial – repetition of the experiment for the same level of the IV • Improvement in experiment: • Increase the number of trials for each time limit from one to three. • Take average of the DV for each value of the IV

  11. Theories and Laws Theory • Well-tested explanation for a broad set of observations Law • A statement that summarizes observations but does not explain them

  12. What is a Model? • A representation • May or may not be to scale • May represent something very large or something very small • Models take many forms… a diagram, a graph, a physical model • Used to help explain a concept

  13. Characteristics of States of Matter

  14. Characteristics of States of Matter

  15. Molecular Representation of States of Matter

  16. How we describe matter Substance • A sample of matter having a constant (uniform or definite) composition. It can be either an element or a compound.

  17. How we describe matter Element • A substance that cannot be decomposed into simpler substances by chemical or physical means. It consists of atoms having the same atomic number.

  18. How we describe matter Compound • A substance with constant composition that can be broken down into elements by chemical processes.

  19. How we describe matter Allotrope • Different forms of the same element Example: Carbon: diamond, graphite, buckyballs Phosphorus: red, white, black

  20. Allotropes of Phosphorus By Weißer_Phosphor.JPG: BXXXD at de.wikipedia Phosphor_rot.jpg: Tomihahndorf Phosphor-rot-violett.jpg: Maksim derivative work: Materialscientist [GFDL (http://www.gnu.org/copyleft/fdl.html) or CC-BY-SA-3.0 (http://creativecommons.org/licenses/by-sa/3.0/)], via Wikimedia Commons https://commons.wikimedia.org/wiki/File%3APhosphComby.jpg White phosphorus can be transformed to red, black or violet by in creasing temperature or pressure

  21. How we describe matter - Particles Atom • Smallest particle of an element that retains the properties of that element; the fundamental unit of which elements are composed

  22. How we describe matter - Particles Molecule • A bonded collection of two or more atoms of the same element or different elements. A representative particle of a molecular compound. Examples: Br2, CH4, H2O

  23. Properties of Matter Extensive property • Depends upon the amount of matter in a sample • Examples – mass, volume Intensive property • Depends upon the type of matter, not the amount • Example – density, absorbancy

  24. Properties of Matter Physical Property • A quality or condition of a substance that can be observed or measured without changing the substance’s composition

  25. Examples of Physical Properties

  26. Properties of Matter Chemical Property • Ability to form new substances

  27. Examples of Chemical Properties Note: The fact that a substance does NOT react is a chemical property

  28. Physical or Chemical Property? • Water melts at 0oC • Propane burns in air • Leaves turn color in the fall • Lead is a very dense metal

  29. Physical and Chemical Changes Physical Change • A change in the physical form of a substance but not its chemical composition; • Chemical bonds are not broken

  30. Physical and Chemical Changes Chemical Change • The change of one substance into another substance through a reorganization of the atoms by breaking or making of chemical bonds; • A chemical reaction

  31. Indicators of Chemical Change • Unexpected color change • Formation of a precipitate • Evolution of a gas • Change in energy

  32. Differentiating Between Physical or Chemical Change • Physical change does not alter the composition of a substance though it may alter the appearance of the substance • Key words • Bend Boil • Break Melt • Crush Solidify • Dissolve Evaporate

  33. Differentiating Between Physical or Chemical Change Examples Salt dissolves in water. Solubility is a physical property so the change is physical. A liquid boils and is converted from a liquid to a gas. Boiling point is a physical property. A change in state is a physical change.

  34. Molecular Description of Change in State

  35. Differentiating Between Physical or Chemical Change Chemical change produces a different substance; composition and properties are different. Requires a chemical reaction to reclaim the starting material. Not always easily done! Reactants  Products

  36. Differentiating Between Physical or Chemical Change Key words that indicate a chemical change: Reacts Precipitates Burn s Explodes Bubbles Emits Fizzes A flame Gives off

  37. Differentiating Between Physical or Chemical Change Examples • A match lights when struck • Substances are combined and light is emitted • An antacid tablet fizzes when added to water

  38. How to differentiate between physical and chemical change • Physical change does not alter the composition of a substance although it may alter its appearance • Chemical change produces a different substance

  39. Mixture A combination of two or more substances that are not chemically combined. The components of the mixture is variable (can be made up differently at different times).

  40. Types of Mixtures Homogeneous Mixture: • Completely uniform in composition • Components are not distinguishable • A solution

  41. Homogeneous Mixtures Examples: • Salt water • Stainless steel • Sugar in water • Gasoline • Brass • Clean air • Jello

  42. Composition of Common Alloys – Solid Solutions

  43. Types of Mixtures Heterogeneous Mixture: • Not uniform in composition • Components are readily distinguishable • Different composition in different parts of the mixture

  44. Heterogeneous Mixtures Examples: • Tossed salad • Soil • Granite

  45. Mixture lingo Phase Any part of a system with uniform composition and properties. Homogeneous mixtures consist of one phase Heterogeneous mixtures consist of two or more phases (e.g., vinegar and oil)

  46. Classification of Matter • Differentiate whether a sample is a substance (element or compound) or a mixture (homogeneous or heterogeneous)

  47. Separation of Mixtures • Mixtures of substances can be separated by physical means. The mixtures may be homogeneous or heterogeneous. One or more processes may be required to separate mixtures. • Make use of type of mixture and physical properties of its components to select the best means of separation.

  48. Techniques for Separation of Mixtures • Filtration • Evaporation • Extraction • Chromatography • Distillation • Decantation • Sieve • Magnet • Centrifuge • Forceps

  49. Examples • Water and salt • Water and ethanol • Salt and sand • Sand and wood chips

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