Chemistry 100 Fall 1999 Dr. Upali Siriwardane CTH 311 Phone Office Hours: Tu,Th, F 8:00-10:00 a.m. M, W 1:00-3:00 p.m. Test 1 : Chapters 1, 2: September 27 Test 2: Chapters 3, 4: October 18 Test 3: Chapters 5, 6: November 10 Make-up, Comprehensive, November 15

KEY CONCEPTS What is chemistry? Physical and chemical changes. Physical and chemical properties. Categories of matter. Separating Mixtures. Scientific Method. Scientific Measurement Observation. & Uncertainty. Significant figure. Precision. Accuracy. Significant figures in calculations. Unit Conversions. Temperature Conversions. Unit conversion method. Density Calculations.

What is chemistry? Chemistry deals with non-reversible changes of matter. Chemistry explains using atoms and molecules. Chemical Concepts and Models improve your problem solving skills Chemistry is a Central Science

What is Matter Matter: Anything that has a mass and volume. The opposite of matter is energy. Matter and Energy is intertwined.

Mixtures Heterogeneous Homogenous Compounds Atoms Electrons Nucleus Protons Neutrons Pure Substances Elements Hierarchy of Matter

How do you Separate Mixtures? Flotation: based on density Filtration: Solid- liquid Distillation- Liquid-liquid Magnetic Separation- Magnetic- Chromatography: 1) Paper 2) Column 3) Gas

What is a Substance? Substance: Substance is what matter is made up of. Substances are either elements or compounds. Pure substances: have characteristic properties such as color, boiling point and reactivity.

What is an Element Element: Elements are substances made up of only one kind of atoms. Eg. oxygen- O 2, iron-Fe, copper-Cu.

What is a Compound? Compounds: Compounds are substances made up of more than one kind of atoms. E.g. Water -H 2 O.

Properties of Substances Physical properties: Physical properties are descriptions of matter such as color, density, viscosity, boiling point, and melting point. Chemical properties: Chemical properties relates to the changes of substances making up the matter. For example, corrosiveness, Flammability

Type of Changes Physical change: A change in the state of matter. It does not involve a change in the substances. E.g. melting of wax and water. Chemical change: A change involving at least one of the substances making the matter. E.g. Electrolysis of water, formation of rust: reaction of iron and oxygen to from iron oxide.

Scientific Method. A method common to all sciences Four Basic Steps: a) Experiment b) Results c) Hypothesis d) Further experiments to test hypothesis

Measurement Measurements or observations are made using our physical senses or using scientific instruments. 1) Qualitative measurements. Changes that cannot be expressed in terms of a number. 2) Quantitative measurements. expressed in terms of a number and an unit.

Measurement Number a) Uncertainty (significant figures) b) Precision c) Accuracy Unit a) basic units b) derived units

Significant Figures: indicate the uncertainty rules to obtain the significant figures Significant 1) Non-zero digits are always significant. 2) Any zeros between two significant digits 3)Trailing zeros in the decimal portion

Not significant 1) leading zeros 2) trailing zeros in whole numbers (use scientific notion to avoid confusion. 3) Exact numbers: unit definition has an unlimited number of sig. digs. 1 ft = 12 in Rounding off: superfluous digit(s) is/are 1) less than 5, the preceding figure is retained. 2. Greater than 5, the last place retained is increased by one 3. Iof the digit 5 exactly rounded off to a even.

Examples sig. digs sig. digs sig. digs … 2 sig. digs. 6.5 x sig. digs sig. digs x 10 5

Significant figure in Calculations 1. Adding/ subtracting numbers. 2. In multiplication and division 3. The root or power of a number 4. Exact Numbers

Adding/ subtracting Arrange the numbers in columnar form. Use most uncertain digit to round off the answer.

multiplication and division the result should have no more sig. digs. than the factor having the fewest number of sig. digs.

Root or Power of a number should have as many sig. digs. as the number itself. Exact Numbers: Numbers coming from definitions such as 12 in = 1 foot. They are not considered in Sig. Fig. Calcualtions.

UNITS

CONVERSION FACTORS convert from one unit to another

Length:1 km = 10 3 m; 1 ft = 12 in; 1 in = 2.54 cm;1 cm = m; 1 yd = 3 ft; 1 m = in 1 mm = m 1 mile = 5280 ft ; 1 mile = km;1 nm = m Volume:1 m 3 = 10 6 cm 3 ;1 gal = 4 qt = 8 pt; 1 ft 3 = L;1 cm 3 = 1 mL; 1 qt = in 3 ;1 L = qt Mass:1 kg = 10 3 g; 1 lb = 16 oz; 1 lb = g; 1 mg = g; 1 short ton =2000 lb 1 g = oz;1 metric ton =10 3 kg 1 metric ton =1.102 short ton

Unit Conversion Method Dimensional(Unit) Analysis Normally calculations are done using an equation. Method of calculations using units a) write the measurement you want convert b)Find all conversion factors needed c) arrange all conversion factors to cancel and to get units of the answer

Factor Label Method 3 km ---> ? m ; conversion factor: 1 km = 1000m 1 km 1000m or m 1 km 1000 m 3 km x = 3000 m 1 km

. Speed of light is 3.00 x 10 8 m s -1. Convert the speed of light to miles per year (1 mile = 1.61 km).

Temperature Conversions o F -- > o C ; C = 5/9 (F - 32) o C -- > o F ; F =9/5 C + 32 o C -- > K ; K = C Human body temperature is 98.6 o F. Convert this temperature to o C and K scale o C = 5/9 ( ) = 5/9 (66.6) = 37.0 o C--> K = 37.0 o C = K

Density Calculations Equation method: Density = mass ÷ volume; d = m/v Factor Label method:14.2 g -- > ? cm 3 conversion factor 2.70 g 1 cm or cm g 14.2 gx 1 cm = 5.26 cm g