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The Science of Chemistry

The Science of Chemistry. Chapter 1 Chemistry I 5.0. Alchemy. How do you picture a chemist?. What is chemistry? . Chemistry is the study of all things and the changes they can undergo. Chemistry is called a central science because it overlaps so many sciences.

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The Science of Chemistry

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  1. The Science of Chemistry Chapter 1 Chemistry I 5.0

  2. Alchemy

  3. How do you picture a chemist?

  4. What is chemistry? • Chemistry is the study of all things and the changes they can undergo. • Chemistry is called a central science because it overlaps so many sciences. • Chemical – is any substance with a definite composition.

  5. What is chemistry? • Changes in chemicals (A.K.A.) chemical changes • The process in which one or more substances change to produce one or more different substances. • Matter – The stuff in which everything is made up of. Matter can be defined as anything with mass and volume.

  6. States of Matter Vibrate Slightly Most Rigid Definite Definite Indefinite Definite Less Rigid Move More Move the fastest Least Rigid Indefinite Indefinite

  7. States of Matter

  8. States of Matter Solid deposition melting sublimation freezing condensing evaporating Liquid Gas

  9. Physical Changes • Do NOT change the identity • Often change what the substance looks like • Examples: mixing ice tea in water, crushing a rock, freezing water

  10. Chemical Changes • Alter the identity of the substance. • The new substance has a different composition than the beginning substances. • Examples: rusting and burning • A shorthand way to express a chemical reaction is with a chemical equation.

  11. Chemical Equations • The substances on the left side of the arrow are called the reactants. They are the starting materials in the reaction. • The substances on the right side of the arrow are called the products. They are the ending materials in a reaction. A + B C + D

  12. Examples of Chemical Equations

  13. Signs of a Chemical Change • Gas production – bubbles, odor, fizz, smoke • Color change • Release or absorption of energy – light or temperature change • Formation of a precipitate – a solid substance that falls out of solution

  14. Law of Conservation of Matter • Matter is neither created nor destroyed, it just changes forms. • Ex.: Where does matter go when you burn a piece of paper?

  15. Describing Matter • Volume – The amount of space an object takes up • Measurement Device: ruler or graduated cylinder

  16. Describing Matter • Mass-The amount of matter in an object • Measurement Device: Balance

  17. Describing Matter • Weight – a measure of the gravitational force exerted on an object • Changes with your location in the universe • Compare mass and weight of a person on earth and on the moon Weight vs. Mass Demo

  18. Types of Measurements • Qualitative: Describes something using the 5 senses • Quantitative: Uses numbers in the description • Quantity – something that has magnitude, size, or amount. • Unit – a quantity adopted as a standard of measurement

  19. International System of Measurements • Based upon multiples of 10 • 7 metric units are base units.

  20. During the18th century scientists measured the distance from the earth’s equator to the North Pole and divided it into ten million parts. This number is equal to exactly 1 meter. Origin of the Metric System

  21. Metric Units • Mass kilogram kg balance • Length meter m ruler • Time second s clock • Temp. Kelvin K thermometer

  22. The Meter • The original standard for the meter was kept in a safe in France. • The meter stick is a replica of that standard. • A meter is made up of 100 centimeters and 1000 millimeters. • Lasers are now used to determine the standard for a meter.

  23. Mass is the amount of matter in an object. 1 cm3 of water = 1 gram. The standard kilogram is kept under lock and key in Washington, DC and other cities around the world. The Gram

  24. Derived Units: Units that come from other units • Area meters squared m2 ruler l x w • Volume meters cubed m3 ruler or graduated cylinder l x w x h

  25. The Liter • The liter is 1000 mL • 10cm x 10cm x 10cm • 1 liter= 1000 cm3 = 1 dm3 • 1 milliliter = 1 cm3 = 1 cc = 20 drops =

  26. Metric (SI) Prefixes • Mega M 1,000,000 • Kilo k 1,000 • Hecto h 100 • Deka da 10 • BASE UNIT • Deci d .1 • Centi c .01 • Milli m .001 • Micro µ .000001 • Nano n .000000001 • Pico p .0000000000001

  27. Properties of Matter • Physical = A characteristic of a substance that does not involve a chemical change • Examples: texture, state of matter, density, hardness, boiling point • Density = The ratio of the mass of a substance to the volume of the substance. • D = mass / volume

  28. Density Column

  29. Density

  30. Which is more dense: Diet or Regular Soda?

  31. Density of an Irregular solid: 1- Find the mass of the object 2- Find the volume if the object by water displacement!

  32. Properties of Matter • Chemical = A property of matter that describes a substance’s ability to participate in chemical reactions. • Examples: reacting with oxygen, light sensitivity

  33. Classification of Matter

  34. Classification of Matter • Pure substances: A sample of matter with a definite composition; means definite chemical and physical properties. • Includes: Elements and Compounds

  35. Elements • Made up of one type of atom. • An atom is defined as the smallest unit of an element that maintains the properties of that element. • Cannot be separated into similar substances by chemical means. • Represented by symbols.

  36. Elements (cont.) • Can exist as atoms or molecules. A molecule usually consists of two or more atoms. • Ex. N2, O2, F2, Cl2, Br2, I2, H2 • Elements that have more than one form are called allotropes. • Ex. Carbon (graphite and diamond)

  37. Compounds • Made up of 2 or more different elements combined in a fixed position. • Can be separated through chemical means. • Represented by formulas. • Electrolysis allows chemists to distinguish between elements in compounds. • Examples: CO2 and H2O

  38. Elements Vs. Compounds

  39. Mixtures: A combination of 2 or more substances that are not chem. combined. • Heterogeneous Mixture: Composed of dissimilar components; Can see the parts • Ex. Cookie, salad, asphalt • Homogenous Mixture: Uniform structure or composition throughout • Ex. Lemonade, steel, air • Alloy: A solid homogeneous mixture (14 caret gold, steel, pewter)

  40. Examples of Alloys Brass is an alloy of copper and zinc. Steel is an alloy of carbon and iron. Bronze is an alloy of copper and tin.

  41. Microscopic look at mixtures

  42. Separating Heterogeneous Mixtures • Filtration: Pour liquid through paper and collect residue (solid)

  43. Separation of Homogeneous Mixtures • Distillation: Separation based on a difference in boiling points

  44. Another Look at Distillation • Distillation Demo • A Closer Look at Distillation

  45. Separation of Homogeneous Mixtures • Crystallization: Evaporate liquid and solid will recrystallize

  46. Separation of Homogeneous Mixtures • Chromatography: Separation of pigments of dye

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