2. Chapter 11 Introduction: Matter and Measurement Chapter 1

3. 2 The Study of Chemistry The Molecular Perspective of Chemistry Matter is the physical material of the universe. Matter is made up of relatively few elements. On the microscopic level, matter consists of atoms and molecules. Atoms combine to form molecules. As we see, molecules may consist of the same type of atoms or different types of atoms.

4. Chapter 13 The Study of Chemistry The Molecular Perspective of Chemistry In these models, we use red to represent oxygen, white to represent hydrogen, and gray to represent carbon.

5. Chapter 14 Classification of Matter States of Matter Matter can be a gas, a liquid, or a solid. These are the three states of matter. Gases have no fixed shape or volume. Gases can be compressed to form liquids. Liquids have no shape, but they do have a volume. Solids are rigid and have a definite shape and volume.

6. Chapter 15 Classification of Matter Pure Substances and Mixtures Atoms consist only of one type of element. Molecules can consist of more than one type of element. –Molecules can have only one type of atom (an element). –Molecules can have more than one type of atom (a compound). If more than one atom, element, or compound are found together, then the substance is a mixture.

7. Chapter 16 Pure Substances and Mixtures Classification of Matter

8. Chapter 17 Pure Substances and Mixtures If matter is not uniform throughout, then it is a heterogeneous mixture. If matter is uniform throughout, it is homogeneous. If homogeneous matter can be separated by physical means, then the matter is a mixture. If homogeneous matter cannot be separated by physical means, then the matter is a pure substance. If a pure substance can be decomposed into something else, then the substance is a compound. Classification of Matter

9. Chapter 18 Pure Substances and Mixtures If a pure substance cannot be decomposed into something else, then the substance is an element. Classification of Matter

10. Chapter 19 Classification of Matter

11. Chapter 110 Classification of Matter Separation of Mixtures Heterogeneous mixtures are not uniform throughout. Homogeneous mixtures can be separated by physical means (e.g., filtration, distillation or chromatography). Compounds can be decomposed into elements. Elements cannot be decomposed any further. Homogeneous liquid mixtures can be separated by distillation. –Requires the different liquids to have different boiling points.

12. Chapter 111 Classification of Matter Separation of Mixtures –In essence, each component of the mixture is boiled and collected. –The lowest boiling fraction is collected first.

13. Chapter 112 Classification of Matter Separation of Mixtures

14. Chapter 113 Classification of Matter Elements There are 114 elements known. Each element is given a unique chemical symbol (one or two letters). They are building blocks of matter. The earth’s crust consists of 5 main elements (shown next slide). The human body consists mostly of 3 main elements (O, C, and H).

15. Chapter 114 Elements Classification of Matter

16. Chapter 115 Classification of Matter Elements Chemical symbols with one letter have that letter capitalized (e.g., H, B, C, N, etc.) Chemical symbols with two letters have only the first letter capitalized (e.g., He, Be).

17. Chapter 116 Classification of Matter Compounds Most elements interact to form compounds. The proportions of elements in compounds are the same irrespective of how the compound was formed. Law of Constant Composition (or Law of Definite Proportions): –The composition of a pure compound is always the same. Therefore, if water is decomposed, then there will always be twice as much hydrogen gas formed as oxygen gas.

18. Chapter 117 Classification of Matter Compounds If water is decomposed (shown here), then there will always be twice as much hydrogen gas formed as oxygen gas.

19. Chapter 118 Properties of Matter Physical and Chemical Changes When a substance undergoes a physical change, its physical appearance changes. –Example: the melting of ice (physical change) results in a solid being converted into a liquid. Physical changes do not result in a change of composition. When a substance changes its composition, it undergoes a chemical change: –When pure hydrogen and pure oxygen react completely, they form pure water. In the flask containing water, there is no oxygen or hydrogen left over.

20. Chapter 119 Physical and Chemical Changes Properties of Matter

21. Chapter 120 Units of Measurement SI Units There are two types of units: –fundamental (or base) units; –derived units. There are 7 base units in the SI system. Derived units are obtained from the 7 base SI units. Example:

22. Chapter 121 SI Units Units of Measurement

23. Chapter 122 Units of Measurement SI Units Powers of ten are used for convenience with smaller or larger units in the SI system.

24. Chapter 123 Length and Mass Note the SI unit for length is the meter (m) whereas the SI unit for mass is the kilogram (kg). –(1 kg weighs 2.2046 lb) Units of Measurement

25. Chapter 124 Units of Measurement Temperature There are three temperature scales: Kelvin Scale Used in science. Same temperature increment as Celsius scale. Lowest temperature possible (absolute zero) is zero Kelvin. Absolute zero: 0 K = -273.15 o C. Celsius Scale Also used in science. Water freezes at 0 o C and boils at 100 o C. To convert: K = o C + 273.15.

26. Chapter 125 Units of Measurement Temperature Fahrenheit Scale Not generally used in science. Water freezes at 32 o F and boils at 212 o F. To convert:

27. Chapter 126 Units of Measurement Temperature

28. Chapter 127 Units of Measurement Volume The units for volume are given by (units of length) 3. –i.e., SI unit for volume is 1 m 3. We usually use 1 mL = 1 cm 3. Other volume units: –1 L = 1 dm 3 = 1000 cm 3 = 1000 mL.

29. Chapter 128 Units of Measurement Density Used to characterize substances. Defined as mass divided by volume. Units: g/cm 3. Originally based on mass (the density was defined as the mass of 1.00 g of pure water).

30. Chapter 129 Volume Units of Measurement

31. Chapter 130 All scientific measures are subject to error. These errors are reflected in the number of figures reported for the measurement. These errors are also reflected in the observation that two successive measures of the same quantity are different. Uncertainty in Measurement

32. Chapter 131 Precision and Accuracy Measurements that are close to the “correct” value are accurate. Measurements which are close to each other are precise. –Measurements can be –accurate and precise; –precise but inaccurate; –neither accurate nor precise. Uncertainty in Measurement

33. Chapter 132 Precision and Accuracy Uncertainty in Measurement

34. Chapter 133 Uncertainty in Measurement Significant Figures The number of digits reported in a measurement reflect the accuracy of the measurement and the precision of the measuring device. All the figures known with certainty plus one extra figure are called significant figures. In any calculation, the results are reported to the fewest significant figures (for multiplication and division) or fewest decimal places (addition and subtraction).

35. Chapter 134 Uncertainty in Measurement Significant Figures Non-zero numbers are always significant. Zeros between non-zero numbers are always significant. Zeros before the first non-zero digit are not significant. (Example: 0.0003 has one significant figure.) Zeros at the end of the number after a decimal place are significant. Zeros at the end of a number before a decimal place are ambiguous (e.g. 10,300 g).

36. Chapter 135 Dimensional Analysis Method of calculation utilizing a knowledge of units. Given units can be multiplied or divided to give the desired units. Conversion factors are used to manipulate units: Desired unit = given unit  (conversion factor) The conversion factors are simple ratios:

37. Chapter 136 Dimensional Analysis Example to convert length in meters to length in inches: length in inches = (length in m)  (conversion factor for m  cm)  (conversion factor for cm  inches). In dimensional analysis always ask three questions: What data are we given? What quantity do we need? What conversion factors are available to take us from what we are given to what we need?

38. Chapter 137 End of Chapter 1 Introduction: Matter and Measurement