Presentation on theme: "Warm-up: Are cell phones and ipods allowed in the classroom? What will happen to them if the teacher sees or hears one (that includes headphones)?"— Presentation transcript:
Warm-up: Are cell phones and ipods allowed in the classroom? What will happen to them if the teacher sees or hears one (that includes headphones)?
Significant Figures - Measurements NO measurement is perfect. – All measurements have an uncertainty. – Human error IS NOT the cause of the uncertainly. Read and record a measurement to one decimal place beyond the smallest marking on that piece of equipment. With a digital device, record all digits.
What is the Length? We can see the markings between 1.6-1.7cm We can’t see the markings between the.6-.7 We must guess between.6 &.7 We record 1.67 cm as our measurement The last digit an 7 was our guess...stop there 3
Accuracy and Precision in Measurements Reading Thermometer 1 Thermometer 2 Thermometer 3 Thermometer 4 199.9°C97.5°C98.3°C97.5°C 2100.1°C102.3°C98.5°C99.7°C 3100.0°C99.7°C98.4°C96.2°C 499.9°C100.9°C98.7°C94.4°C Average99.98°C100.1°C98.5°C96.9°C Range0.2°C5.0°C0.4°C5.3°C Accurate Precise YES YES YES YES NO NO NO NO
To number or not to number, that is the question….. Observations or data that deals with numbers is called QUANTITATIVE. Observations or data that does NOT deal with numbers is called QUALITATIVE.
Qualitative or Quantitative? 1. There are 6 tables in the room – A) Qualitative – B) Quantitative 2. The room is hot – A) Qualitative – B) Quantitative 3. This powerpoint sucks – A) Qualitative – B) Quantitative 4. There are lot of people in this room – A) Qualitative – B) Quantitative
Types of Quantitative Information There are 2 types of quantitative data – Exact Anything that is counted – Ex. I have 10 fingers and 10 toes Exact relationships or predefined values – 12 inches = 1 foot – 1 dozen = 12 – Inexact (measured) Anything that you measure using a tool (ruler, scale, thermometer, etc) – The paper is 8.5 inches wide
Exact or Inexact #’s 5. 1 yard = 3 feet – A) Exact – B) Inexact (measured) 6. The diameter of a red blood cell is 6 x 10 -4 cm. – A) Exact – B) Inexact (measured) 7. There are 2 doors in this room. – A) Exact – B) Inexact (measured) 8. Gold melts at 1064°C – A) Exact – B) Inexact (measured)
Warm-up Come up with an example of the following: Exact number Inexact number Quantitative observation Qualitative observation
Significant Figures The significant figures (sig figs) of a number are those digits that carry meaning contributing to its precision. Exact numbers have an infinite number of sig figs Inexact numbers have a finite number based on rules of sig figs.
Significant Figures All non-zero numbers are always significant. Then use the following to determine if zeros are significant. – Determine if number has a decimal point. – If it does, look from left to right for the first non-zero digit. All digits after it are significant – If it does not, go from right to left looking for the first non-zero digit. All digits after it are significant.
Significant Figures – Zero Rules A zero in the number Decimal Count from Left No Decimal Count from Right
Counting Sig Figs No decimal 2543 SF 304,9004 SF
Counting Sig Figs with Decimal 0.004503 SF 7 SF 1,000.000
Practice: How Many Sig Figs? 0.00003280 g 1000 mL 3.14 m 21.001 cm 3 SF 5 SF 1 SF 4 SF
Sig. Figs. in Calculations Addition and Subtraction By doing a math operation, you can not increase the number of significant figures! Addition and Subtraction – count DECIMAL PLACES – The number of decimal places in your answer should match the digit with the smallest number of decimal places.
Sig. Figs. in Calculations Multiplication and Division Multiplication and Division – Count SIGNIFICANT FIGURES. – The number of significant figures in your answer should match the digit with the smallest number of significant figures.
Adding & Subtracting Sig Figs 3.224 cm + 1000.3 cm = 1003.5 cm Estimated value
Practice 56.333 g + 1.0007 g = 25.005 L + 38.1 L = 0.01 g + 1.11 g = 3000 N + 144.2 N = 63.105= 63.1 L 57.3337 = 57.334 g 1.12 3144.2 g = 3144 N 1.12
Multiplying & Dividing Sig Figs 6.0 cm X 22.0 cm = 2 SF 3 SF 132 =130 cm 2 2 SF
Practice 56.3 g 33 mL = 4.0 m X 22.3 m = 0.21 cm X 1.11cm X 2.0 cm = 89.2 = 89 m 2 1.7060606 = 1.7 g/mL 0.4662 0.47 cm 3