Chapter 3- Measurement This powerpoint highlights what you should know and be able to do for the chapter 3 test. Reading this will NOT guarantee you an A, but it is a good place to start your studying. Slides should be further investigated in your text and with practice problems.

Skills and Knowledge Differentiate between qualitative and quantitative observations and interpretations. *Qualitative observations are those which we use our senses to get. They refer to the properties of something. For example: color, texture, luster, and smell. *Quantitative observations have to do with the numerical quality of something. For example: length, mass, reaction time, and pH. *Interpretations are when you use your prior knowledge to draw a conclusion based on your sensory perceptions. For example, you have a white, crystalline solid and you say it is salt. RED APPLE

Skills and Knowledge Appropriately use measurement tools in the laboratory. Record measurements to the correct number of sig figs, with the correct uncertainty value, and with the correct label. * Record all digits that are known for sure plus one uncertain digit. We know 20.3 for sure and can estimate the hundredths place to be.08 so the measurement is mL. The uncertainty is +/ mL.

Skills and Knowledge Identify the number of significant figures in a number. *4 rules about zeroes: Captive zeroes, and trailing zeroes after a non-zero digit after the decimal count. Trailing zeroes without a decimal point and leading zeroes do not count. *All nonzero digits count. *Counting numbers and standard conversion factors are said to have unlimited sig figs. They do not affect the number of sig figs in a calculation.

Skills and Knowledge Use the rules of significant figures in calculations to correctly round off numbers and perform addition, subtraction, multiplication and division. * When adding or subtracting, your answer should contain the same number of decimal places as the measurement with the LEAST number of decimals. 3.45g + 2 g = 5 g *When multiplying or dividing, your answer can have the same number of sig figs as the measurement with the FEWEST sig figs cm x 2.1 cm = = 7.2 cm 2

Skills and Knowledge Differentiate between accuracy and precision. *Accuracy is how close a measurement is to the true or accepted value. *Precision is the reproducibility of a measurement on a given instrument. A calibrated instrument will be accurate and precise. *Precision may also refer to the sensitivity of an instrument. The more markings, the more precise.

Skills and Knowledge Calculate the density of an object from experimental data. Find the mass, volume or density of a substance when any two of these values are known. Differentiate between specific gravity and density. *D = m/v Density is the amount of matter packed into a given space. It is a unique property of substances. *Specific gravity is the density of a substance compared to the density of another substance, usually water. It has no units.

Skills and Knowledge Calculate % error in a determined value. % error = experimental – accepted x 100% accepted *Experimental value is the data you get in lab. *The accepted value is looked up in a book, on a manufacturer’s web site, or may be the average of class data.

Skills and Knowledge Convert between Celsius and Kelvin. *Celsius = Kelvin – 273 or, Kelvin = Celsius *The size of a degree is the same for both scales. *Celsius is used in the lab, but calculations are done in Kelvin. *Absolute zero on the Kelvin scale is the lowest temperature possible. It is the slowest possible motion for atoms.

Skills and Knowledge Differentiate between the mass and weight of an object. *Mass is the amount of “stuff” in an object. *Weight is a measure of gravity’s pull on an object and thus it can change with position. For example, on the moon where gravity is less than on the earth, you would weigh less but have the same mass. beyondbooks.com

Skills and Knowledge Identify the metric units of length, mass, time and volume. Differentiate between basic and derived units. *The metric units are: meter, gram, second, and liter. *The basic units are the SI units: meter, kilogram, second, mole, Kelvin, (and candela, Joule, and ampere.) *Derived units are combinations of the above units or are converted from the above units. For example, Hertz is s -1 and a Newton of force is m kg s -2

Skills and Knowledge Identify the common metric prefixes and convert measurements within the metric system...

Skills and Knowledge Construct conversion factors from equivalent measurements. 1 dollar = 4 quarters = 10 dimes so we can write 6 conversion factors: 1 dollar = 4 quarters = 10 dimes = 1 dollar = 10 dimes 4 quarters1 dollar 1 dollar 10 dimes 4 quarters And 4 quarters 10 dimes These all have a value of one and thus they do not change the value in a calculation, only the unit.

Skills and Knowledge Apply the techniques of dimensional analysis to a variety of conversion problems. Use dimensional analysis to solve multi-step problems. Dimensional analysis requires you to use conversion factors. Units cancel out and can tell you if you have done the problem correctly. Your car's gas tank holds 18.6 gallons and is one quarter full. Your car gets 16 miles/gal. You see a sign saying, "Next gas 73 miles." Your often- wrong brother, who is driving, is sure you'll make it without running out of gas. You're not so sure and do some quick figuring: