Chapter 1 Elements and Measurements Students are responsible for all sections in this chapter Dang

Some Chemical Properties of the Elements Matter: Describes anything with a physical presence—anything you can touch, taste, or smell. Physical Properties: Characteristics that do not involve a change in a sample’s chemical makeup. Chemical Properties: Characteristics that do involve a change in a sample’s chemical makeup. Chemical properties and chemical changes are synonymous. Dang

The Metric System (SI) The metric system or SI (international system) is a decimal system based on 10. used in most of the world. used everywhere by scientists. All other units are derived from these fundamental units Dang

For numbers greater than or equal to 1000 and less than or equal to 0 For numbers greater than or equal to 1000 and less than or equal to 0.001 it is common to use scientific notation.

Derived units SI units of measurements comprised of a combination of the seven base units Dang

Writing scientific notation To write large or small numbers Dang

Measuring Mass Mass: Amount of matter in an object. Weight: Measures the force with which gravity pulls on an object. Dang

Measuring Temperature Dang Measuring Temperature TF = 1.8 TC + 32 TC = (TF – 32) 1.8 One degree Fahreheit is 100/180 = 5/9 the size of a degree Celsius or a kelvin. K = °C + 273.15

Accuracy, Precision, and Significant Figures Significant figures: The number of meaningful digits in a measured or calculated quantity. They come from uncertainty in any measurement. Generally the last digit in a reported measurement is uncertain (estimated). Exact numbers and relationships (7 days in a week, 30 students in a class, etc.) effectively have an infinite number of significant figures. Dang

A Measurement the unit tells you what standard you are comparing your object to the number tells you what multiple of the standard the object measures the uncertainty in the measurement scientific measurements are reported so that every digit written is certain, except the last one which is estimated If the length is reported as 3.26 cm, the digits 3 and 2 are certain (known). the final digit, 6, is estimated (uncertain). all three digits (2, 7, and 6) are significant, including the estimated digit.

Known & Estimated Digits For the following volume readings, what would be measured values? ________ ________ E.g l8. . . . l . . . . l9. . . . l . . . . l10. . cm What is the length of the line? 1) 9.2 cm 2) 9.13 cm 3) 9.19 cm

Accuracy, Precision, and Significant Figures 1 2 4 3 cm What is the length (units) of the black rectangle above? Dang

Uncertainty in Measured Numbers accuracy is an indication of how close a measurement comes to the actual value of the quantity precision is an indication of how reproducible a measurement is

Accuracy, Precision, and Significant Figures Significant figures: The number of meaningful digits in a measured or calculated quantity. They come from uncertainty in any measurement. Generally the last digit in a reported measurement is uncertain (estimated). Exact numbers and relationships (7 days in a week, 30 students in a class, etc.) effectively have an infinite number of significant figures.

Examples Classify each of the following as (1) exact or (2) measured numbers. A.__Gold melts at 1064 °C. B.__1 yard = 3 feet C.__The diameter of a red blood cell is 6 x 10-4 cm. D.__There are 6 hats on the shelf. E.__A can of soda contains 355 mL of soda.

Accuracy, Precision, and Significant Figures Rules for counting significant figures (left-to-right): Zeros in the middle of a number are like any other digit; they are always significant. 4.803 cm 4 sf 2. Zero at the beginning of a number are not significant (placeholders). 0.00661 g 3 sf or 6.61 x 10-3 g 3. Zeros at the end of a number and after the decimal point are always significant. 55.220 K 5 sf 4. Zeros at the end of a number and after the decimal point may or may not be significant. 34,2000 ? SF Dang

Rounding Numbers If the first digit you remove is less than 5, round down by dropping it and all following numbers. 5.6654 = 5.665 2. If the first digit you remove is 6 or greater, round up by adding 1 to the digit on the left. 5.6656 = 5.666 3. If the first digit you remove is 5 and there are more nonzero digits following, round up. 5.664 525 = 5.665 4. If the digit you remove is a 5 with nothing following, round down. 5.664 525 = 5.664 52 Books sometimes use different rules for this one. Dang

Multiplication and Division When multiplying or dividing the final answer must have the same number of significant figures as the measurement with the fewest significant figures. Example: 110.5 x 0.048 = 5.304 = 5.3 (rounded) 4 SF 2 SF calculator 2 SF Dang

Addition and Subtraction When adding or subtracting the final answer must have the same number of decimal places as the measurement with the fewest decimal places. 25.2 one decimal place + 1.34 two decimal places 26.54 calculated answer 26.5 final answer with one decimal place Dang

Calculations: Converting from One Unit to Another Dimensional analysis: A method that uses a conversion factor to convert a quantity expressed in one unit to an equivalent quantity in a different unit. Conversion factor: States the relationship between two different units. original quantity x conversion factor = equivalent quantity Dang

Conversion Factors A conversion factor is obtained from an equality. Equality: 1 in. = 2.54 cm written as a fraction (ratio) with a numerator and denominator. inverted to give two conversion factors for every equality. 1 in. and 2.54 cm 2.54 cm 1 in. may be obtained from information in a word problem and is written for that problem only. Example : The cost of one gallon (1 gal) of gas is $4.29. 1 gallon of gas and $4.29 $4.29 1 gallon of gas Dang

Example: Convert 1.76 yards to centimeters How many ounces are in 1.0 kg? How many in3 in 1.5 m3 Dang

Examples If your pace on a treadmill is 65.0 meters per minute, how many minutes will it take for you to walk a distance of 45.0 miles? Dang

Derived Units: Density and Its Measurement Density is temperature dependent. Solids: cm3 Liquids: mL Gases: L Density = Volume Mass Typical volume units

Density Ratio of mass:volume is an intensive property value independent of the quantity of matter Solids = g/cm3 1 cm3 = 1 mL Liquids = g/mL Gases = g/L Volume of a solid can be determined by water displacement – Archimedes Principle Density : solids > liquids >>> gases except ice is less dense than liquid water! For equal volumes, denser object has larger mass For equal masses, denser object has smaller volume Heating an object generally causes it to expand, therefore the density changes with temperature

Density Density compares the mass of an object to its volume. is the mass of a substance divided by its volume. Density Expression Density = mass = g or g = g/cm3 volume mL cm3 Note: 1 mL = 1 cm3 Can we use density as a conversion factor to calculate mass or volume?

Examples Osmium is a very dense metal. What is its density in g/cm3 if 0.11 lb of osmium has a volume of 2.22 ml? The density of octane, a component of gasoline, is 0.702 g/mL. What is the mass, in kg, of 875 mL of octane? Dang