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Chem101 Chapter 01 Chemical Foundations

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**What is chemistry? The science that explains:**

the properties of materials how new materials may be made the relationship between energy and chemical reactions how materials may be analyzed at the atomic and molecular level (Macroscopic & Microscopic. A key concept is that chemists look for explanations

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**1.1Chemistry: An overview**

Chemistry is fundamentally concerned with: "How one substance changes to another" How plants grow by absorbing water and Carbon dioxide? How humans manufacture the proteins from the food we consume? ….. and on and on A substance is composed of atoms, all universe is made of only 110 {different types of atoms}

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1.2 The Scientific Method It is a systematic approach to research that includes: Making Observation Making a Prediction "Hypothesis" Doing Experiment to test the Hypothesis Law: summary of observed behavior Theory: model attempt to explain

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**a number and a scale (unit)**

1.3 Units of Measurement Quantitative Measurement, consists of two parts: a number and a scale (unit) In 1960, an international agreement get up a system of units called International System (SI- system) based on metric system.

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**Prefixes: are used to change the size of the unit**

1.3 Units of Measurement Prefixes: are used to change the size of the unit Table 1.2 Prefixes Used with SI Units Prefix Symbol Meaning Tera- T 1012 Giga- G 109 Mega- M 106 Kilo- k 103 Deci- d 10-1 Centi- c 10-2 Milli- m 10-3 Micro- 10-6 Nano- n 10-9 Pico- p 10-12

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**{SI derived unit for volume is cubic meter (m3)}**

1.3 Units of Measurement Volume is not fundamental SI – unit, but very commonly used in chemistry, {SI derived unit for volume is cubic meter (m3)} 1 m3 = (10 dm)3 = 1000 dm3 = 1000 L Used unit in liter = 1dm3 1 L = 1dm3 = (10 cm)3 = 1000 cm3 (ml)

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**1.4 Uncertainty in measurement**

Any measurement always has some degree of uncertainty. Uncertainty depends on the precision of measuring device. e.g., measurement of volume of a liquid using a buret: the used liquid is about ………………….mL If 4 different people read the same volume we might get: Person Result 1 22.2 2 22.1 3 22.3 4 22.0

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**1.4 Uncertainty in measurement**

You have to record the certain digits and the first uncertain digit only. All digits together [ certain + first uncertain] are called " Significant Figures" The uncertainty in the last number must be assumed to be # 1 Volume = 22.2 ± 0.1 ml Example 1.1: What is the difference between the measurements 25.00mL and 25mL?

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**Precision and Accuracy**

1.4 Uncertainty in measurement Precision and Accuracy Not Accurate Not precise Accuracy: it is the agreement of a particular value with the true value. Precision: it is the agreement among several measurements of the same quantity. Not Accurate But precise Accurate and precise

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**Errors 1.4 Uncertainty in measurement**

Large Random Error Random error: it means that a measurement has an equal probability of being high or low. Systematic error: error accurse in the same direction each item. Small Random and Large Systematic Error Small Random And NO Systematic Error

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**1.5 Significant Figures (SF) and Calculations**

Rules for Counting Significant Figures: It is important to be applied to get the uncertainty in the final results out of adding, subtracting multiplying ..etc. Nonzero integers, count as SF. Zeros: - "Leading zeros” are not significant. e.g (2 SF) - "Captive zeros” Count as s.f. e.g.: (4 SF) - "Trailing zeros” count as s.f. eg. : 100 = 1.00 X 102 (3 SF) Exact numbers have an infinite number of SF e.g. 10 experiment, 5 apples, 8 books … so on. .. Exponential notation: it is used to unite large or small numbers in the correct sig.fig. e.g convenient 6.0 x 10-5

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**1.5 Significant Figures (SF) and Calculations**

Rules for SF in Mathematical Operations: Multiplication / Division: Final results have the same SF in the least precise measurement used in calculation. e.g x 1.4 = 6.38 = (………………?) Addition / Subtraction: Final results have the same number of decimal places as the least precise numbers e.g = = (…………?)

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**1.5 Significant Figures (SF) and Calculations**

Note: To get the correct total SF in the final results you may round off the results. Rules for rounding: if the number to be removed is < 5, the preceding digit stays the same. e.g., round 1.33 to 2 S.F. (…………?) Exercise 1.4: a) 1.05 x 10-3 ÷ = (………….?) b) 21 – 13.8 = (……………?)

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**1.6 Dimensional Analysis 7.00 in = 17.8 cm**

conversion of a given results from one system unit to an other using "Unit Factor Method" or dimensional analysis. Means Multiply any expression by "1" will not change its value. Exercise 1.5: A pencil is 7.00 in long, What is its length in centimeter? Solution: what is the in/cm relation: 2.54cm = 1 in which unit is needed: cm unit factor must has cm unit as nominator. i.e cm / 1 in = 1 [unit factor] Multiply the length by the unit factor gives: 7.00 in x 2.54 cm /1 in = 17.8 cm 7.00 in = 17.8 cm

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**1.6 Dimensional Analysis Note:**

Sometime you have to do multi-step conversion to get correct answer. Exercise 1.7: A student has entered a 10.0 km race. How long is the run in miles? Solution: km m yd mi [1 km = 1000m, 1 m = 1.09yd, 1760yd = 1 mi] Results: 10.0 km = 6.22 mi

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**1.7 Temperature Adjust the zero difference Tc = (TF-32oF) x 5oF/ 9oC**

Engineering Science Difference Is complicated Difference Is in their zero Conversion Adjustment in the degree step Adjustment in the zero Conversion Adjust the zero difference Tc = (TF-32oF) x 5oF/ 9oC TF = (T0C x 9oF/5oC) + 32oF T(Kelvin) = T(oC)

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**1.8 Density It is the mass per unit volume of the substance.**

A property of matter that is often used by chemists. Density = Exercise 1.13: A chemist finds that 25.00cm3 of a CD- cleaner has a mass of g at 20oC. The following are the names and densities of the compounds that might be the main component: Which of them is the most likely to be the main component of the CD-cleaner? Solution: Chloroform 1.492 g / cm3 At 20oC Diethyl ether 0.714 Ethanol 0.789 Isopropyl alcohol 0.785 Toluene 0.867

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**1.9 Classification of matter**

Read (pp ) and Report (HW#2): Define : "Matter, Mixtures, Physical changes, Compound, and Element" Define: "Distillation, Filtration, and Chromatography.

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**What is this apparatus? What is its main opeation?**

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