General Chemistry CHEM 112 -Ch1-1st 2024 PDF

General Chemistry For Students of Medical Colleges Chem 112 - Credit hrs: 3 King Abdulaziz University Faculity of Science Chemistry Department The Study of Change Chapter 1  Objectives By the end of this chapter, you should be able to: ▪ Know the SI basic quantities an...

General Chemistry For Students of Medical Colleges Chem 112 - Credit hrs: 3 King Abdulaziz University Faculity of Science Chemistry Department The Study of Change Chapter 1  Objectives By the end of this chapter, you should be able to: ▪ Know the SI basic quantities and their SI units. ▪ Convert between units and use the prefixes. ▪ Know how to derived units from the SI basic units. ▪ Define common units of volume and density ▪ Know the temperature Scales. 3  Outline Chemistry by Chang, 10th ed, Chapter 1 ▪ SI unit Introduction ▪ (Prefixes, Units conversion) ▪ SI Derived Units ▪ Mass and Weight ▪ Volume ▪ Density ▪ Temperature Scale 4  Introduction ▪ Chemistry: is the study of matter and the changes it undergoes. ▪ Matter: is anything that occupies space and has mass ▪ Substance: is a form of matter that has a definite composition and distinct properties. 5 5  Matter Pure substance Mixture Element Molecules and Compounds Homogeneous Heterogeneous ❑ Pure substance: it is a form of matter that has a definite ❑ Mixture: it is a combination of two or more substances in which (constant ) composition and distinct properties. Examples: the substances retain their distinct identities. Examples: Air, soft water, sugar and gold. drink, and pizza. 1) An element is a substance that cannot be separated into 1) A homogeneous mixture is a gaseous, liquid or solid mixture that simpler substances by chemical means. has the same proportions of its components throughout a given 2) A molecule is a substance composed of atoms of one or sample. There is only one phase of matter observed. Example: more elements chemically united in fixed proportions. sugar in water Example: molecular oxygen, water, ammonia. The 2) A heterogeneous mixture is a mixture in which the composition is compound should be composed of two or more elements. not the same uniform. Example: fruit salad 6  Chapter One / Introduction States of matter Gas Liquid Solid Molecules are separated by distance. Molecules are close together but not held so Molecules are held close together in orderly rigidly in position and can move past on another fashion with little freedom of motion. Have no definite shape. Have no definite shape Have a definite shape Have no definite volume. Have a definite volume Have a definite volume 7  Introduction ▪ A physical change: does not change the composition or identity of a substance e.g. ice melting or salt dissolving in water ▪ A chemical change: changes the composition or identity of the substance/s involved e.g. hydrogen burn in air to form water Hydrogen burns in air to form water 8  Measurement The International System of units (SI Units) ❑ The benefit of the SI units is making technical information is effectively communicated, transcending the variations of language. ❑ Values of quantities are expressed using Arabic symbols for numbers paired with a unit symbol 9  Measurement (Prefixes) ❑ Unit symbol, often used with a prefix symbol that modifies unit magnitude (multiple or fraction). ❑ In general, prefixes are used with any SI units. ❑ The choice of prefixes for a unit has arisen by convenience of use and historical developments. 10  Unit conversion: 1- prefix to Base unit To remove a prefix from a value, insert the numerical value of the prefix in place of the symbol. Example: convert 8.53 pm to meters? Replace p with x 10-12, therefore the answer is 8.53 x 10-12 m 2- Base unit to prefix To insert a prefix into a value, insert both the prefix and the inverse of its numerical number. Example: convert 0.000462 g to milligrams ? 0.000462 x 103 mg = 0.462 mg 3- prefix to prefix ( in two steps: prefix to base unit followed by base unit to prefix) Example: convert 6 km to nm? First convert km to m → Replace k with x 103, therefore the answer is 6 x 103 m Then convert m to nm → Insert both the prefix and the inverse of its numerical number 6 x 103 x 10+9 = 6x1012 nm 11  ‫‪ -1‬التحويل بين وحدات أكبر من الوحدة األساسية‬ ‫)‪Tera (1012‬‬ ‫)‪kilo (103‬‬ ‫‪ 1012-3 ➔  109‬‬ ‫‪ -2‬التحويل بين وحدات أصغر من الوحدة األساسية‬ ‫)‪dece (10-1‬‬ ‫)‪nano (10-9‬‬ ‫‪ 10-1-(-9) ➔  108‬‬ ‫‪ -3‬التحويل بين وحدات تمر بالوحدة األساسية‬ ‫)‪Mega (106‬‬ ‫)‪nano (10-9‬‬ ‫‪ 106-(-9) ➔  1015‬‬  Examples ‫االس الذي يمثل الوحدة التي ترغب‬ ‫التحويل منها‬ ‫االس الذي يمثل الوحدة التي ترغب‬ ‫التحويل اليها‬ 1. Convert 134 pm to m? Or How many meters are in 134 pm? Current prefix - Desired prefix ×10 134 ×10-12 m = 1.34×10-10 m -12 – (0) ×10 2. How many microseconds are in a second? a) 1 x 10-1 1 s = ? µs b) 1 x 10-6 c) 1 x 10-15 d) 1 x 106 1 × 10+6 µs 0 – (-6) ×10 13  Chapter One / Introduction Measurement in chemistry How many second are in a microseconds ? (a) 1 x 10-1 (b) 1 x 10-6 (c) 1 x 10-15 (d) 1 x 10 6 Which of the following is the smallest distance? (a) 21 m (b) 2.1 x 102 cm (c) 21 mm Put all of them in the same unit (d) 2.1 x 104 pm 14  SI Derived Units SI derived units: are defined in terms of the seven base quantities via a system of quantity equations. Examples Area = width x length Unit of Area = m× m = m2 Volume = width x length x height Unit of Volume = m× m x m = m3 15  Volume ▪ SI derived unit for volume is cubic meter (m3) ▪ Common unit of volume is liter (L) and milliliter (ml) ▪ The relation ship between liter (L) and (ml) 1L= 1000mL ▪ The relation ship between liter (L) and metric system 1 L = 1dm3 ▪ The relation ship between milliliter (ml) and metric system 1 mL = 1cm3 16  Mass and Weight ▪ Mass: is the measure of the amount of matter in an object. ▪ The SI unit of mass is the kilogram (kg) 1 kg = 1000 g = 1 x 103 g ▪ Weight: is the measurement of the pull of gravity on an object. The weight of man on earth is 50 pounds. >> 8.25 pounds on moon ▪ Chemist are interested primarily in mass. ▪ The Mass of an object doesn't change when an object's location changes. Weight, on the other hand does change with location. 17  Density Mass (g) ▪ Density is defined as the amount of matter in a given amount of space. Density Volume (g/ml) (ml) mass density = volume d = m/V ▪ SI derived unit for density is kg/m3. ▪ Common units of density are g/mL , g/L. ▪ Density decrease with temperature. ▪ (g/ml )(g/cm3) for liquid and solids ▪ g/L = 0.001g/ml for gases because density of gases are very low 18  Example 1. A piece of platinum metal with a density of 21.5 g/cm3 has a volume of 4.49 cm3. What is its mass? d = m/V m=dxV = 21.5 g/cm3 x 4.49 cm3 = 96.5 g Extra practice: Examples 1.1 & 1.2, Chemistry by Chang 10th ed 19 ▰ Example A piece of silver (Ag) metal weighing 194.3 g is placed in a graduated cylinder containing 242.0 mL of water. The volume of water now reads 260.5 mL. From these data calculate the density of silver? volume of silver = volume of water (after) – volume of water ( before ) = 260.5 – 242.0 = 18.5 ml d = m/V = 194.3 / 18.5 = 10.5 g/ml 20 1 Which of the following is not an SI base unit? A) kilometer B) kilogram C) second D) kelvin 2. Which of the following SI base units is not commonly used in chemistry? A) kilogram B) kelvin C) candela D) mole 3 Which of the following prefixes means 1/1000? A) kilo B) deci C) centi D) milli 4. The SI prefixes giga and micro represent, respectively: A. 10-9 and 10-6. B. 106 and 10-3. C. 103 and 10-3. D. 109 and 10-6. E. 10-9 and 10-3. 5. What is 22.6 m when converted to decimeters? A) 0.226 dm B) 2.26 dm C) 226 dm D) 2.26 x 10–3 dm 6. What is 25.4 mg when converted to kilograms? A) 2540 kg B) 2.54 x10–5 kg C) 2.54 kg D) 2.54 x 104 kg  Temperature Scales There are several temperature scales, the most commonly used one are: 1. Fahrenheit scale (Degrees Fahrenheit 0F) 2. Celsius scale (Degrees Celsius 0C) 3. Kelvin scale (K) Kelvin is the SI Base Unit of Temperature 23  Temperature Scales 1. Degrees Celsius 0C: Scaled based on the boiling point and freezing point of water (100 → 0) 2. Kelvin K: K = 0C + 273.15 3. Degrees Fahrenheit 0F : Scaled based on the freezing point of salty water (0 0F) and the body temperature (assigned to 96 0F) and hence pure water assigned the temperatures 32 and 212 as freezing and boiling points respectively. Thus: the size of degree in 0F scale is only 100/180 or 5/9 of a degree on the 0C scale 24  Temperature Units Conversion ❖ To convert degrees Celsius to degrees Fahrenheit °F = [ (9/5) × °C] + 32 ❖ To convert degrees Fahrenheit to degrees Celsius °C = (5/9) (°F - 32) ❖ To convert degrees Celsius to kelvin ° K = °C + 273.15 No relationship between Kelvin and degrees Fahrenheit Thus: K → 0C → 0F or 0F → 0C → K 25  Example 1. Convert 224 0C to degrees Fahrenheit? °F = [(9 /5 )× °C] + 32 °F = [(9 /5 ) × 224 °C] + 32 = 435 0F Extra practice: Example 1.3, Chapter 1, Chemistry by Chang, 10th ed 26