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Chemistry

Chemistry. Introduction. Menu. Definitions Classification of Matter Properties of Matter Measurement and SI Units Working with Numbers. Quit. Definitions. Matter is anything that occupies space and has mass. Chemistry is the study of matter and the changes it undergoes

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Chemistry

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  1. Chemistry Introduction

  2. Menu • Definitions • Classification of Matter • Properties of Matter • Measurement and SI Units • Working with Numbers Quit

  3. Definitions • Matter is anything that occupies space and has mass. • Chemistry is the study of matter and the changes it undergoes • A substance is matter that has a definite or constant composition and distinct properties Examples are water, silver, sugar, table salt, etc.

  4. Classification of Matter Matter Mixtures Pure Substances Separation by Physical Methods Homogeneous Mixtures Heterogeneous Mixtures Compounds Elements Separation by Chemical Methods

  5. Properties of Matter Physical Property Chemical Property Extensive Property Intensive Property

  6. Physical Property A physical property can be measured and observed without changing the composition of a substance. Examples: Boiling Point Density Conductivity

  7. Chemical Property A chemical property refers to the ability of a substance to react with other substances. In order to observe this property a chemical change must take place. Examples: Sugar ferments to form alcohol Hydrogen burns in oxygen to create water.

  8. Extensive Property Measurable properties which depend on the amount of substance present are called extensive properties. Examples: Mass Length Volume

  9. Intensive Property Measurable or observable properties which are independent of the amount of substance present are called intensive properties. Examples: Color Density Temperature

  10. Measurement and SI Units SI units are an international standard of units developed in 1960 based on the decimal (base 10) system. Base Quantity Name of Unit Symbol Length meter m Mass Kilogram kg Time second s Temperature kelvin K Amount of Substance mole mol

  11. Length Length measures the extent of an object. Length can be used to determine derived units such as area and volume. Area = m x m = m2 Volume = m x m x m = m3 1 Liter (L) = 1dm3 (One cubic decimeter) 1 milliliter (mL) = 1cm3 (One cubic centimeter) 1 L = 1000 mL Density d = m/V (mass per unit volume)

  12. Mass Mass is a measure of the quantity of matter inside of a substance or object. It should not be confused with the term weight, which is a measure of the force that gravity exerts on an object. They are related by the following equation; F = mg where g is the acceleration due to gravity, m is the mass and F is the force in Newtons In chemistry, the smaller unit of mass grams (g) is preferable to kilograms (kg). 1kg = 1000g

  13. Temperature Temperature measures the average kinetic energy of the particles contained within a system or object. Although Kelvin are the accepted SI unit, the Celsius scale is often used. Both are based on the decimal system. The Fahrenheit scale is seldom used for scientific measurement. Refer to the next frame for a comparison of temperature scales and conversion factors.

  14. Temperature Comparisons and Conversions 373 100 212 Water Boils oF = 9/5 oC + 32 oC = (oF - 32)5/9 K = oC + 273 Body Temperature 310 37 98.6 298 25 77 Room Temperature 273 0 32 Water Freezes Kelvin Celsius Fahrenheit K oC oF

  15. Working With Numbers Scientific Notation Significant Figures Accuracy and Precision Factor-Label Method of Solving Problems

  16. Scientific Notation Allows representation of large or small numbers accurately. Removes possible ambiguity about significant figures. Numbers are expressed follows; N x 10n where N is a number between 1 and 10 and n is an integer exponent that is positive if the decimal point is moved to the left to make N between 1 and 10, and negative if it must be moved to the right.

  17. Examples 1. The number 5,876.73 is expressed in scientific notation as; 5.87673 x 103 2. The number .000034785 is expressed as; 3.4785 x 10-5

  18. Addition and Subtraction 1. Write each number so that n has the same exponent 2. Add or subtract the N parts of the numbers 3. The exponent n remains the same Example: 2.3x104 + 1.5x103 would be rewritten as 2.3x104 + .15x104 and the final answer would be 2.45 x 104.

  19. Multiplication and Division 1. Multiply or divide the N parts of the numbers together 2. Add the exponents, n, if multiplying 3. Subtract exponents if dividing Example: 3.0x103 x 4.0x104 = 12x107 = 1.2x108

  20. Significant Figures Significant figures refer to the meaningful digits in a measured or calculated quantity The last digit is understood to be uncertain when significant figures are counted

  21. Guidelines • Any digit that is not zero is significant • Zeros between nonzero digits are significant • Zeros to the left of the first nonzero digit are not significant • If a number is greater than 1, then all the zeros written to the right of the decimal point count as significant figures • For numbers that do not contain decimal points, the trailing zeros (zeros after the last nonzero digit) may or may not be significant. This is one reason why it is important to use scientific notation

  22. Calculations Involving Sig Figs Addition and Subtraction: The number of digits to the right of the decimal point in the final answer is determined by the lowest number of significant figures to the right of the decimal in any of the original numbers Multiplication and Division: The number of significant figures in the final answer is determined by the original number that has the smallest number of significant figures Exact numbers (from definitions or by counting) are considered to have an infinite number of significant figures For chain (multiple) calculations, carry the intermediate answers to one extra decimal place and round the final answer to the correct digits

  23. Accuracy and Precision Accuracy tells how close a measurement is to the true value of the quantity that was measured Precision refers to how closely two or more measurements of the same quantity agree with one another Precise but not accurate Neither precise nor accurate Precise and accurate

  24. Dimensional Analysis(Factor Label Method) Allows accurate conversion between units of similar types It utilizes the fact that equivalent quantities using different units may be set up as a ratio to convert from one type of unit to another Algebraically, labels are treated exactly the same way as the numbers they refer to The unit you are converting to should always be placed in the ratio such that the old units cancel out and the new unit is in the desired position whether numerator or denominator

  25. Examples 1in = 2.54cm therefore the ratio 1in/2.54cm or 2.54cm/1in may by used to convert centimeters to inches or inches to centimeters, respectively 100in x (2.54cm/1in) = 254cm 1km = 0.6215mi 10km x (0.6215mi/1km) = 6.215mi

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