FUNDAMENTALS OF CHEMISTRY Dr. Sulaiman Al-Sulaimi Chemical Foundations BY Dr. Sulaiman Al-Sulaimi Assistant Professor UNIVERSITY OF NIZWA

INTRODUCTION Chemistry: the branch of science concerned with the substances of which matter is composed, the investigation of their properties and reactions, and the use of such reactions to form new substances. Science: A process for understanding nature and its changes to explain phenomena of the physical world. Matter: Anything which has some mass and occupies some space. Examples: water, gold, NaCl, sugar, Air etc.

Scientific Method 4.Theory: A set of tested hypothesis that explains To understand any process that lies at the center of scientific inquiry. Steps in the Scientific Method are: 1. Making observations: (collecting data). 2. Hypothesis: A possible explanation for an observation. 3. Performing experiments: to test the prediction or hypothesis (testing the hypothesis). 4.Theory: A set of tested hypothesis that explains some natural phenomena. ( summary of why it happened). 5. Law: observed behavior formulated into statement is called Law (Summary of what happened).

Observations: are of two types; 1- Qualitative Observations: It does not involve a number. Example; sky is blue, Water is liquid. 2- Quantitative- involves both a number and a units. Example: Water boils at 100 oC, road length is 100 kilometer. The Various Parts of the Scientific Method

QUESTION Generally observed behavior which can be formulated into a statement, sometimes mathematical in nature, is called a) observation. b) measurement. c) theory. d) natural law. e) experiment

QUESTION A quantitative observation a) contains a number and a unit. b) does not contain a number. c) always makes a comparison. d) must be obtained through experimentation. e) none of these

QUESTION Which of the following is an example of a quantitative observation? a) The piece of metal is longer than the piece of wood b) Solution 1 is much darker than solution 2. c) The liquid in beaker A is blue. d) The temperature of the liquid is 60°C. e) At least two of the above (a-d) are quantitative observations.

Fundamental Quantities and Units In 1960, an international agreement set up a system of units called the International System or the SI system. This system is based on the metric system and units derived from the metric system.

Fundamental Quantities and Units Physical Quantity Units Abbreviations Mass kilogram kg Length meter m Time second s Temperature Kelvin k Electric Current Ampere A Amount of substance mole mol Luminous Intensity candela cd

SI System Example: Mass unit is kilogram(kg), length unit is meter(m). Volume is not a fundamental SI unit but is derived from length. Cubic meter (m3) is more commonly used is liter/(L). 1 liter= 1 dm3 = (10cm)3 = 1000 cm3 1 cm3 = 1 mL 1000 mL = 1 Liter

Larger and Smaller Units p = pico (0.000000000001) 10-12 n = nano (one billionth) 10-9 µ = micro (0.000001) 10-6 m = milli (0.001) 10-3 c= centi (0.01) 10-2 10o = 1 Larger units h= hecto 102 k = kilo (1000) 103 M = mega (1000000) 106 G = giga (1000000000) 109 11

QUESTION Which of the following metric relationships is incorrect? a) 1 microliter = 10–6 liters b) 1 gram = 103 kilograms c) 103 milliliters = 1 liter d) 1 gram = 102 centigrams e) 1liters = 106 microliter

Uncertainty in measurement What is a measurement? A measurement tells us about a property of something. It might tell us how heavy an object is, or how hot, or how long it is. A measurement gives a number to that property. What is uncertainty of measurement? The uncertainty of a measurement tells us something about its quality. Uncertainty of measurement is the doubt that exists about the result of any measurement. You might think that well-made rulers, clocks and thermometers should be trust worthy, and give the right answers. Every measurement has some degree of uncertainty. 13

Uncertainty in measurement person Results of measurements 1 43.30 2 43.40 3 43.35 The above results show that the first two numbers (43) remain the same regardless of who makes the measurement; these are called as CERTAIN digits. However, the digits to the right side of the decimal point must be estimated and therefore varies, called as an UNCERTAIN digits. Certain digits are known as Significant figures of a measurement. The uncertainty of any measurement is indicated by ±value. For example, in above case the uncertainty is 43 ± 0.1 You may be interested in uncertainty of measurement simply because you wish to make good quality measurements and to understand the results. Two terms are usually used to describe the reliability of any measurement; precision and accuracy. 14

Precision and Accuracy It determines how closely several Measurements (results) of the same quantity agree with each other. It shows the reproducibility of a given type of measurement. 1st series of measurements: 34, 35, 37, 37, 38 2nd series of measurements: 30, 35, 40, 42, 47 The precision of the 1st series is better than the 2nd series. Accuracy: It determines how closely several Measurements (results) of the same quantity agree with the true value (standard value). Example: True Value = 37.0 Average = Sum of all the values / number of values Example: 34, 36, 39, 40 sum of all the values = 149 number of values = 4 average = 149/4 = 37.2 true value = 37.0  good accuracy. 15

Errors Random Error (indeterminate error): A measurement has an equal probability of being high or low. This type of error occurs in estimating the value of the last digit of measurement. Systematic Error (Determinate error): This type of error occurs in the same direction each time. It is either always high or always low, often resulting from poor technique. 16

Precision and Accuracy No Precision No accuracy Precision but not accuracy Accuracy The Difference between Precision and Accuracy 17

QUESTION A titration was performed to find the concentration of hydrochloric acid with the following results: Trial Molarity 1 1.25 ± 0.01 2 1.24 ± 0.01 3 1.26 ± 0.01 The actual concentration of HCl was determined to be 1.000 M; the results of the titration are: a) both accurate and precise. b) accurate but imprecise. c) precise but inaccurate. d) both inaccurate and imprecise. e) accuracy and precision are impossible to determine with the available information.