INTRODUCTION: MATTER AND MEASUREMENT

1. INTRODUCTION:MATTER AND MEASUREMENT Chapter 1

2. Classifications of Matter Solid rigid, definite volume and shape. Liquid relatively incompressible fluid, definite volume, takes shape of container. Gas easily compressible fluid, no fixed volume or shape.

3. The three forms of matter - solid, liquid and gas - are referred to as the states of matter.

4. Pure Substances and Mixtures • A puresubstanceis a kind of matter that cannot be separated into other kinds of matter by any physical process. • A mixture is a material that can be separated by physical means into two or more substances.

5. Get two types of mixtures: • A homogeneous mixture is a mixture that is uniform in its properties throughout given samples. • A heterogeneous mixture is a mixture that consists of physicallly distinct parts, each with different properties. Note: A phase is one of several homogeneous materials present in the portion of matter under study.

7. Separation of Mixtures • Examples to separate heterogeneous mixtures: • - Magnetic • Filtration • Examples to separate homogeneous mixtures: • Distillation • - Chromatography

8. Basic Distillation Setup

9. Separation of Mixtures by Paper Chromatography

10. Separation of Mixtures by Column Chromatography

11. Elements and Compounds • Laviosier defined an element as a substance that cannot be decomposed by any chemical reaction into simpler substances.

12. A compound is a substance composed of two or more elements chemically combined.

13. Physical and Chemical Changes • A physical change is a change in the form of matter but not in its chemical identity.Example: - Dissolution of salt. • - Distillation • A chemical change or chemical reaction is a change in which one or more kinds of matter are transformed into a new kind of matter or several new kinds of matter. Example: • - The rusting of iron.

14. Not in Book! Intensive vs Extensive Properties • Extensive property: is dependent on the amount of substance in a system. eg. mass, volume etc. • Intensive property: is NOT dependent on the amount of substance in a system. eg. density, temperature, pressure etc.

15. In flow-diagram form:

16. Physical Measurements Chemists characterise and identify substances by their particular properties. To determine many of these properties requires physical measurements. In a modern chemical laboratory, measurements often are complex, but many experiments begin with simple measurements of mass, volume, time, and so forth.

17. Units of Measurement Any measurement consists of three interlinked concepts: a measured number a unit a measure of the uncertainty If you repeat a particular measurement, you usually do not obtain precisely the same result, because each measurement is subject to experimental error.

18. The Length of a Steel Rod

19. SI Base units and SI Prefixes • The International System or SI was adopted in 1960 and is a particular choice of metric units. • There are seven base units from which all other units can be derived. • In SI a larger or a smaller unit for a physical quantity is indicated by a SI prefix.

20. SI Base Units

21. SI Prefixes

22. Length, Mass and Time Self study

23. Temperature

24. Converting from one temperature scale to another

25. Not in Book! Example: In winter the average low temperature of interior Alaska is –30°F. What is the temperature in degree Celsius? And in Kelvin?

26. Derived SI units

27. Area • Once base units have been defined for a system of measurement, then other units can be derive. SI unit of area = (SI unit of length) x (SI unit of length)

28. Volume Volume is defined as length cubed and has the SI unit of cubic meter (m3). 1 L = 1 dm3    and    1 mL = 1 cm3

29. m = d v Density The density of an object is its mass per unit volume. Suppose an object has a mass of 15.0 g and a volume of10.0 cm3

30. Which is more dense?

31. Not in Book! Calculating the Density of a Substance Alternate Example Oil of wintergreen is a colourless liquid used as a flavouring. A 28.1 g sample of oil of wintergreen has a volume of 23.7 ml. What is the density of wintergreen?

32. Not in Book! m = d v Alternate Example Using Density to relate Mass and Volume A sample of gasoline has a density of 0.718 g/mL. What is the volume of 454 g of gasoline?

33. Dimensional Analysis Dimensional analysis  the method of calculation in which one carries along the units for quantities • The advantages of this are: • The correct units for the answer follow automatically. • Errors are more easily identified. eg. when the final units are nonsense

34. Example Calculate the volume, V, of a cube, given s, the length of one of its sides. V = s3 , if s = 5.00 cm NO guesswork in the final units

35. Converting Between Units. What is 5 liters in terms of cm3? We know: 1 mL = 1 cm3

36. Not in Book! Alternate Example Converting Units: Metric Unit to Metric Unit A sample of sodium metal is burned in chlorine gas, producing 573 mg of sodium chloride. How many grams is this? How many kilograms? 573 mg

37. Not in Book! Converting Units: Metric Volume to Metric Volume An experiment calls for 54.3 mL of ethanol. What is the volume in cubic meters?

38. Number of Significant Figures • Number of significant figures  number of digits reported for the value of a measured or calculated quantity, indicating the precision of the value. • Scientific notation is the representation of a number in the form: A x 10n eg. 3x10-8 m

39. Sig. Fig. Rules! • All digits are significant except zeros at thebeginning of the number and possibly terminal zeros.eg. 0.00231 59000 • Terminal zeros ending at the right of the decimal point are significant.eg. 0.2540 • Terminal zeros in a number without an explicit decimal point or may not be significant.

40. Not in Book! Determine the number of sig. fig.’s in the following: 27.53 cm 39.240 cm 102.0 g 0.00021 kg 0.06080 L 0.0002 L

41. Sig. Fig.’s in Calculations • Multiplication and division: • result must have as many sig. fig.’s as there are in the measurement with the least number of sig. fig.’s. • Addition and Subtraction: • result must have same number of decimal places as there are in the measurement with the least number of decimal places.

42. 0.0634 g cis-platin 100.0 g of water x 25.31 g of water Example: Suppose you have a substance believed to be cis-platin and, in an effort to establish its identity, you measure its solubility. You find that 0.0634 g of the substance dissolves in 25.31 g of water. The amount dissolving in 100.0 g is :

43. In performing the calculation 100.0 X 0.0634 ÷ 25.31, the calculator display shows 0.2504938. We would report the answer as because the factor has the least number of significant figures

44. Exact Numbers & Rounding • An exact number is a number that arises when you count items or sometimes when you define a unit. • The conventions of significant figures do NOT apply to exact number. eg. suppose you want the total mass of 9 coins when each coin has a mass of 3.0 grams. The calculation is: • Rounding is the procedure of dropping nonsignificant digits in a calculation and adjusting the last digit reported.

45. Not in Book! 5.8914 1.289 x 7.28 Example Perform the following calculations, rounding the answers to the correct number of sig.fig.’s.

46. Not in Book! One more Example 92.34 x (0.456 - 0.421) =