Presentation on theme: "SI units and Sig. Figs. measurement. SI (système internationale) Physical Quantity UnitSymbol Volume Cubic Metre (litre) m3m3m3m3 LengthMetrem MassKilogramkg."— Presentation transcript:
SI units and Sig. Figs. measurement
SI (système internationale) Physical Quantity UnitSymbol Volume Cubic Metre (litre) m3m3m3m3 LengthMetrem MassKilogramkg TimeSeconds TemperatureKelvinK Amount of substance Molemol Electric current AmpereA Luminous intensity Candelacd
Scientific Notation Scientists have developed a shorter method to express very large numbers. Scientific Notation is based on powers of the base number 10.
Scientific notation 123,000,000,000 in s.n. is 1.23 x The first number 1.23 is called the coefficient. It must be between The second number is called the base. The base number 10 is always written in exponent form. In the number 1.23 x the number 11 is referred to as the exponent or power of ten. This large number only has 3 significant digits
To write a large number in scientific notation: ex: First put the decimal after the first digit and drop the zeroes. Ex: 3.6 Next, count the number of places from the decimal to the end of the number. Ex: 4 Finally, put it together. Ex: 3.6 x only has two significant digits
To write a small number in s.n. ex: First move the decimal after the first real number and drop the zeroes. Ex: Next, count the number of places moved from the original decimal spot to the new decimal spot. Ex: 2 Numbers less than 1 will have a negative exponent. Ex: -2 Finally, put it together. Ex: x has four significant digits
Precision: to describe how well a group of measurements made of the same object or event under the same conditions actually do agree with one another. These points are precise with one another but not accurate.
Accuracy: represents the closeness of a measurement to the true value. Ex: the bulls-eye would be the true value, so these points are accurate.
Why Significant Figures? When we take measurements or make calculations, we do so with a certain precision. This precision is determined by the instrument we use to take those measurements. So, when we do calculations based on our measurements, the calculations must be only as precise as the measurements.
Using sig figs: The Rules! 1.Digits from 1-9 are always significant. 2.Zeros between two other significant digits are always significant 3.One or more additional zeros to the right of both the decimal place and another significant digit are significant. 4.Zeros used solely for spacing the decimal point (placeholders) are not significant. 487 All significant 2002 All significant 6.00 All significant Only two significant digits
EXAMPLES # OF SIG. DIG. COMMENT 453kg3 All non-zero digits are always significant. 5057L4 Zeros between 2 sig. dig. are significant Additional zeros to the right of decimal and a sig. dig. are significant Placeholders are not sig.
Problems: Indicate the number of significant figures ______ ______ ______ ______ ______ ______ ______ ______ ______ ______
Multiplying and Dividing RULE: your answer may only show as many sig figs as the multiplied or divided measurement showing the least number of significant digits. Example: cm x 3.10 cm = 69.3 only 3 sig figs allowed.
Multiplying and Dividing Practice x 2.61______ x 0.23______ ÷ 1.21______ ÷ 4.1______ x 42.1______ x 0.02______ ÷ 0.023______ x 23______ ÷ 0.12______ x 12 ÷ 12.5______
Adding and Subtracting: RULE: your answer can only show as many decimal places as the measurement having the fewest number of decimal places. Example: 3.76 g g + 2. g = 20. g 3.76 g g g = 20.7 g
Adding and Subtracting Practice ______ ______ ______ ______ ______ ______ ______ ______ ______ ______