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## 8/27/14

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**8/27/14**• Today I will use the steps of the scientific method to solve problems. • Warm Up – What is the scientific method?**Measurements and Math**Academic Chemistry Chapter 1 (Sections 4-7)**Scientific Method**• What is the scientific method? • A way of answering questions about the world we live in • Why do we use the scientific method? • Organization • Communication • Common sense**Scientific Method**• Steps • 1. Identify the problem or question • 2. Gather information and make observations • 3. Form a hypothesis • 4. Test the hypothesis (experiment) • 5. Analyze the data and form a conclusion**Scientific Method**• Hypothesis - • educated guess • can never truly prove correct • Theory – • well tested hypotheses about a topic • Law – • Hypothesis or theory that has been tested over and over and generally accepted as fact by the scientific community**Scientific Method**• Controlled experiment • Experimental Group – vary one variable while keeping all others constant • Control Group – do not make any changes in order to compare to the experimental group**Scientific Method**• Independent Variable • Variable that is changed in a scientific experiment • What we control • Dependent Variable • Variable that changes in relation to the independent variable • What we measure • Control Variables • Things we purposely keep constant in an experiment**8/28/14**• Today I will demonstrate the steps of the scientific method. • *Please take out your homework and put on your desk. • Warm Up – Find your pulse on your wrist or your neck. Count how many beats you feel in 10 seconds.**8/29/14**• Today I will review algebraic concepts. • Warm Up – Solve for x: 3(4x + 7) = 45**9/2/14**• Today I will measure objects to the correct degree of certainty Warm Up – I want to see if using the air conditioner in my car really uses more gas. If I design an experiment to test this, what is the dependent variable and what is the independent variable?**What is Chemistry?**• Chemistry – The study of matter and the changes it undergoes • The central science! • Chemistry overlaps so many other fields and professions!**Measurements**• A measurement consists of a number and a unit. • That boy is almost 7 tall. Seven what?? That boy is almost 7 feet tall.**Measurement**• Metric System • SI units – base units • Length - meter • Mass– gram (kilogram) • Volume - liter • Time – second • Temperature – Kelvin**Measurement**• Metric System • Derived units – made up of bases • Area → a = l x w Meter squared (m2) • Volume → v = l x h x w meter cubed (m3)**Making Measurements**• Uncertainty in measurement • When measuring, estimate the measurement to one place past the last place on the instrument. • Measuring Length**Making measurements**Remember to estimate! • Measuring Mass • Triple beam balance • Electric balance Estimation done for you!**Making Measurements**Measuring Volume • Volume of a liquid -read the bottom of the meniscus -usually mL**Making Measurements**Measuring Volume • Volume of a liquid • Volume of a regular solid -geometry equations -cm*cm*cm=cm3 -1mL = 1cm3 11.32 cm 6.85 cm 5.90 cm**Making Measurements**Measuring Volume • Volume of a liquid • Volume of a regular solid • Volume of an irregular solid -water displacement**Reliability**• Precision • Will give the same number over and over again • Accuracy • Will be close to the accepted value**9/3/14**• Today I will determine the number of significant figures in a number. • Warm Up- Measure the following with both rulers:**Significant Figures**• In measurements, the certain and estimated digits together are the significant figures.**Significant Figures**• Four easy rules!!! #1 All Nonzero numbers are SIGNIFICANT! 324.5**Significant Figures**• Four easy rules!!! #2 All “sandwiched” zeroes are SIGNIFICANT! 3204.05 3004.05**Significant Figures**• Four easy rules!!! #3 All leading zeroes are NEVER SIGNIFICANT! 0.0320405**Significant Figures**• Four easy rules!!! #4 Trailing zeroes are SIGNIFICANT if there is a decimal point anywhere in the number! 0.032040 3200 3200. 3200.00**Significant Figure Practice**• 0.057010 • 0.0026701 • 19.0550 • 3500 • 123 • 0.200 • 80000 • 5 significant figures • 5 significant figures • 6 significant figures • 2 significant figures • 3 significant figures • 3 significant figures • 1 significant figure**Rounding**• Round the following numbers to 3 significant figures: 0.057010 0.0026701 19.0550 35800 1232264 0.2 85421.55 1822449 Do I have the correct number of significant figures? Does the number still mean the same thing?**Measuring & Sig Fig Practice**• Use a ruler to measure the object given to the correct place. • How many significant figures does this number have?**9/4/14**• Today I will demonstrate measuring various quantities. • Warm Up – Describe the measurement process**9/5/14**• Today I will determine the number of significant figures in a calculation • Warm Up – How many significant figures are in the number : 0.002001100**Significant Figures in Calculations**• Multiplications and Division • The measurement with the smallest number of significant figures determines the number of significant figures in your answer.**Significant Figures in Calculations**• Multiplications and Division 3.052 m x 2.10 m x 0.75 m 2 4 3 = 4.8069 m3 = 4.8 m3**Significant Figures in Calculations**• Addition and Subtraction • The measurement with the largest uncertainty determines the number of significant figures in your answer.**Significant Figures in Calculations**• Addition and Subtraction 3.052 m - 2.10 m + 0.75 m = 1.702 m 3.052 m - 2.10 m +0.75 m 1.702 m = 1.70 m**Significant Figures in Calculations**• Addition and Subtraction 951.0 g + 1407 g + 23.911 g + 158.18 g 951.0 g 1407 g 23.911 g 158.18 g 2540.091 g = 2540. g**9/8/14**• Today I will convert numbers to scientific notation • Warm Up – Calculate the following to the correct number of significant figures: (3.440)(0.0021)(3009)**Scientific Notation**• For very large or very small numbers! • 1,000,000,000,000,000,000,000,000,000,000,000 • 0.00000000000000000000000000000000000001 Makes difficult numbers easier to use!**Putting Numbers into Scientific Notation**• For numbers greater than one: • 145,000 • Place a decimal point after the first significant figure • Add x 10 • Count the number of places the decimal moved and place it as a positive exponent on the ten. 5 x 10 1.45000**Putting Numbers into Scientific Notation**• For numbers less than one: • 0.01450 • Place a decimal point after the first significant figure • Add x 10 • Count the number of places the decimal moved and place it as a negative exponent on the ten. -2 x 10 1.450**Putting Numbers into Regular Notation**• For numbers greater than one (positive exponent): • 1.45 x 105 • Move the decimal to the right the number of spaces indicated by the exponent 145,000**Putting Numbers into Regular Notation**• For numbers less than one (negative exponent): • 1.450 x 10-2 • Move the decimal to the left the number of spaces indicated by the exponent 0.01450**Scientific Notation**• Remember!!! • Bignumbers are positive! • Small numbers are negative!**Scientific Notation**• Try these: • 432400000 • 0.0000000000003 = 4.324 x 108 = 3 x 10-13**Calculators and Scientific Notation**• To put this number into your calculator, you must use the exponent key. • Let’s find it!**Calculators and Scientific Notation**• 6.4 x 10-12 • To put this number into your calculator, you must use the exponent key. 6.4 EE -12**Scientific Notation**• Do this math on your calculator: • 2.34 x 106* 5.63 x 10-12 • 6.54 x 1013/ 4.31 x 102 • 2.3 x 103 + 5.3 x 102 • 4.2 x 1023 – 1.8 x 1022 = 1.32 x 10-5 = 1.52 x 1011 = 2.8 x 103 = 4.0 x 1023**9/9/14**• Today I will practice significant figures and scientific notation. • Warm Up – • Write 574000 in scientific notation • Write 2.1 x 107 in regular notation • Calculate: 2.1 x 103 ÷ 5.2 x 104 5.74 x 105 21000000 4.04 x 10-2 (0.0404)