Chapter 1:Fundamental Concepts and Units of Measurement

1. Brady & Senese 5th Ed Chapter 1:Fundamental Concepts and Units of Measurement

2. Chemistry- the study of the composition of matter and its transformations Matter- anything that takes up space and has mass Chemical reaction- change that results from the interaction of matter. 1.1. Chemistry is important for anyone studying the sciences Chemistry and the Sciences

3. 1.2. The scientific method helps us build models of nature Scientific Method : Getting Started

4. 1.2. The scientific method helps us build models of nature Scientific Method: Testing the Hypothesis

5. A theory isanexplanation (based on well-tested, internally consistent experimental results) about why the phenomenon may occur • it should explain currently available data • It should be as simple as possible • It should clearly show underlying connections • It should accurately predict future behaviors 1.2. The scientific method helps us build models of nature The Scientific Method- Evaluating The Data

6. Chemical change- a process that results in the formation of a new substance Evidence? Formation of a new solid, new liquid, new gas, temperature change, or an unexpected color change Physical change- a process that results in no new substance, but that may change the state of those present, or the proportions 1.3. Matter is Composed of Elements, Compounds, and Mixtures Changes in Matter

7. Matter is either a pure substance or a mixture Mixtures may be separated using physical methods such as chromatography, filtration, sieving 1.3. Matter is Composed of Elements, Compounds, and Mixtures Matter Can Be Classified By Its Properties:

8. Elements - substances that cannot be decomposed into simpler substances shown on the periodic table as symbols: “K” for potassium and “Na” for sodium made of identical atoms, either singly or in groups 1.3. Matter is Composed of Elements, Compounds, and Mixtures What Is An Element?

9. 1.3. Matter is Composed of Elements, Compounds, and Mixtures What Is A Compound? • Compounds - formed from two or more atoms of different elements combined in a fixed proportion • Have different characteristics than the elements that compose them • Can be broken down into elements by some chemical changes

10. mixtures consist of varying amounts of two or more elements or compounds • Homogeneous mixtures or “solutions”- have the same properties throughout the sample • Brass, tap water • Heterogeneous mixtures-consist of two or more phases • Salad dressing, Coca-Cola ™ 1.3. Matter is Composed of Elements, Compounds, and Mixtures Mixtures

11. Classification by state is based on packing, motion, and shape • Solids have fixed shape and volume • Liquids have fixed volume, but take the container shape • Gases have to expand to fill the shape and volume of the container 1.4. Properties of matter can be classified in different ways Classification Of Matter By State

12. Chemical properties describe the behavior of the matter that leads to the formation of a new substance: the "reactivity" of the substance Physical properties can be observed about the matter alone, without changing the composition 1.4. Properties of matter can be classified in different ways Properties Of Matter

13. Intensive properties are independent of sample size • Examples: color, texture and temperature • Extensive properties depend on sample size • Examples: volume and mass • Properties used to identify substances are always intensive • Density, color, and texture are often helpful in identification, but temperature is not 1.4. Properties of matter can be classified in different ways Intensive And Extensive Properties

14. Qualitative observations are non-numerical-- ask “what” or “how” or “why” Quantitative observations are numerical--ask “how much” and are also called measurements This course is general chemistry with quantitative analysis 1.5 Measurements are essential to describe properties Measurements are Observations

15. Always involve a comparison Require units Involve numbers that are inexact (estimated). This uncertainty is due to the limitations of the observer and the instruments used In science, all digits in a measurement up to and including the first estimated digit are recorded 1.5 Measurements are essential to describe properties Measurements:

16. In the U.S., we use the Imperial(USCS)System • The scientific community (and most of the world) uses the metric system • Variations in the metric system exist, thus a standard system is used: International System of Units (SI) • SI units we will use now: • Length (m) Mass (kg) Time (s) Temperature (K) 1.5 Measurements are essential to describe properties Measurements and units

17. involve a combination of base units, including: 1.5 Measurements are essential to describe properties Derived units Measurement Formula SI Units Area length × width m2 Volume length × width × height m3 Velocity distance/time m/s Acceleration velocity/time m/s2 Density mass/volume kg/m3

18. 1.5 Measurements are essential to describe properties You May Encounter Non-SI Metric Units:

19. measured directly, using equipment for volumetric measure calculated using dimensional (length) information and appropriate formulas. 1 cm3= 1mL USCS: fl. oz., pt., qt., gal Metric: L, cm3 SI: m3 1.5 Measurements are essential to describe properties Volume-bulk

20. 1.5 Measurements are essential to describe properties Temperature Conversions

21. Because each measurement involves an estimate, measurements always have error. Record all measured numbers, including the first estimated digit These digits are called significant digits or significant figures Exact numbers have infinite significant digits 1.6. Measurements always contain some uncertainty Measurement Error

22. Using the first thermometer, the temperature is 21.3 ºC (3 significant digits) Using the more precise (second) thermometer, the temperature is 21.32 ºC (4 significant digits) 1.6. Measurements always contain some uncertainty Significant Digits In A Measurement Are Limited By Instrument Precision

23. Errors-inherent error due to the equipment or procedure • Changing volume due to thermal expansion or contraction (temperature changes) • Improperly calibrated equipment • procedural design allows variable measurements • Mistakes-blunders that you know that you have made. Do not use these data • Spillage • Incomplete procedures • Reading scales incorrectly • Using the measuring device incorrectly 1.6. Measurements always contain some uncertainty Errors Arise From A Number Of Sources Including:

24. Errors can often be detected by making repeated measurements Error can be reduced by calibrating equipment The average or meanreduces data variations: it helps find a central value 1.6. Measurements always contain some uncertainty Reducing Error:

25. Non-zero digits are significant Zeros between significant digits are significant Zeros to the right of non-zero digits in a number that contains a decimal point are significant (Trailing with a decimal point) Zeros to the left of the first nonzero digit are never counted as significant (Leading) Zeros at the end of a number without a decimal point are assumed not to be significant (Trailing without a decimal place) 1.6. Measurements always contain some uncertainty Rules For Significant Figures (Sig Figs)

26. 1.7 Units can be converted using the factor-label method Unit Conversions • Suppose we wish to convert 25 miles to km. Further, we know that there are .6215 miles in a km. • We can assemble a ratio and solve this problem. • easy enough because we have a direct conversion between the units • Often, we must piece together multiple steps and this approach is impractical

27. 1.7 Units can be converted using the factor-label method USCS Unit Conversions

28. 1.7 Units can be converted using the factor-label method Learning Check: Write all conversion factors needed to convert the following: • 33 in to yd • 450 c to gal • 56 y to s • 25 mph to ft/s • 12 in.=1 ft • 3 ft =1 yd • 2 c.=1 pt. • 2 pt.=1 qt. • 4 qt.=1 gal. • 60 s=1 min • 60 min=1 h • 24 h=1 da • 365.25 da=1 y • Distance: 3 ft=1 yd; 1760 yd=1 mi • Time: 60 s=1 min; 60 min=1 h

29. Convert the following: • 3.03 g to tons • 0.545 ft. to km • 5.22 y to s • 25 mph to km/s 1.7 Units can be converted using the factor-label method Learning Check: • 3.34(10-6) T • 1.66(10-4) km • 1.65(108) s • 1.1(10-2) km/s

30. intensive property defined as the ratio of an object’s mass (m) to volume (v), d = m/v characteristic of pure substances at a specified temperature Since most substances expand when heated, densities decrease when heated. units : g/L for gases and g/mL for solids and liquids. 1.8. Density is a useful intensive property Density(d)