1. Chapter 3 Scientific Measurements

2. Describe the following object in your notes

3. Qualitative vs. Quantitative Qualitative: gives results in a descriptive nonnumeric form Ex: large & small Quantitative: gives results in a definite form, usually in numbers Ex: 121cm

4. Accuracy vs. Precision Accuracy: is a measure of how close a measurement comes to the actual or true value. Correctness Poor accuracy results from procedural or equipment flaws Good accuracy

5. Accuracy vs Precision Precision: is a measure of how close a series of measurements are to one another. Reproducibility Poor precision results from poor technique Good precision

8. Determining Error

9. What is the percent error of a measured value of 114 lbs if the person’s actual weight is 107 lbs?

10. Scientific Notation Used when working with large or very small numbers Used when working with large or very small numbers #’s less than 1 have negative exponents #’s less than 1 have negative exponents 0.00036 = 3.6 x 10 -4 0.00036 = 3.6 x 10 -4 #’s greater than 1 have positive exponents #’s greater than 1 have positive exponents 36,000 = 3.6 x 10 4 36,000 = 3.6 x 10 4

11. DO NOW: Significant Figures Sig. Figs. Sci. Notation 1.0.0034133.41 x 10 -3 2.1.004051.0040 x 10 0 3.0.0000515 x 10 -5 4.6500026.5 x 10 4 5.4030034.03 x 10 4 6.20030042.003 x 10 5 7.0.050035.00 x 10 -2 8.2.420 x 10 12 4done

12. DO NOW: Significant Figures 5.910 x 10 8 4591,000,000 L5. 8.8 x 10 3 28792 L4. 6164.32 x 10 -1 dm 3. 1.8 x 10 -3 20.00177 cm2. 3.147 x 10 2 4314.721 m1. Wrong measurements correct Correct Answers sig. figs. The following measurements are not in the correct sig. figs. Rewrite them so that they show the correct number of sig. figs. Put all answers in scientific notation.

13. Dimensional analysis The skill of converting from one unit to another The skill of converting from one unit to another EX: 10 meters is how many millimeters 13 days is how many seconds 13 days is how many seconds

14. Units Get Larger (always make larger unit = 1) Katie Hates Dogs b/c Dogs Can’t Meow 10 3 10 2 10 1 BASE UNIT meter literGram 10 -1 10 -2 10 -3 kilohectodecadecicentimilli 1,000m in 1 km 100m in 1 hm 10 m in 1dam 10 dm in1m100cmin 1 m 1,000mmin1m

15. Conversion Factor A fraction that always equals 1. A fraction that always equals 1. EX: 1km = 1,000m put into a fraction 1 km or 1,000m 1,000m 1 km Both fractions equal 1

16. EXAMPLE Problem #1: 12 m=?cm STEPS 1. Write the given 12m 2. Draw the conversion line 12m 3. Find a conversion factor. 100cm = 1m 4. Place what unit you want to get rid of opposite the given. 12m m 12m m

17. 5. Place the unit you want at the same level as the given.12m cm m 6. Fill in the #’s of the conversion factor. 12m 100 cm 1 m 7. Cancel units 12m 100 cm 1 m 8. Multiply everything on top, multiply everything on the bottom, and then divide SO……….12m = 1,200cm SO……….12m = 1,200cm

19. Chapter 17 Thermochemistry

20. Thermochemistry The study of energy changes that occur during chemical reactions and changes in state.

21. Thermochemistry Energy: the ability to do work or to supply heat ENERGY (Joule or calorie) = HEAT (J or cal) 1 cal = 4.18 J Chemical Potential Energy: stored energy in chemicals chemicals

22. Heat vs. Temp. Heat and temperature are concepts that are often confused

23. Heat vs. Temp. Amount of energy in a system Degree of hotness or coldness of an object Form of energy Measures the average kinetic energy of molecules Flows from a warmer object to a cooler one It is measured in Joules or calories It is measured in degrees

24. Calorie vs. calorie Calorie = refers to food (dietary) Calorie = 1kilocalorie = 1,000 calories Snickers Bar = 280 Calories = 280 kilocalories = 280,000 calories = 280,000 calories calorie= a unit of heat

25. Specific Heat Capacity The amount of heat it takes to raise the temperature of 1 g of a substance 1 o C q =m Δ T C p q =m Δ T C p q =heat energy (J or cal) q =heat energy (J or cal) m =mass (g) m =mass (g) Δ T =(T f – T i ) = o C Δ T =(T f – T i ) = o C C p = specific heat = C p = specific heat = J = heat (J) J = heat (J) g x o C mass (g) x (T f – T i ) g x o C mass (g) x (T f – T i )

26. Q =m Δ T C p q = g o C J g x o C g x o C When units are canceled, q = Joules

27. Specific Heat Capacity The amount of heat it takes to raise the temperature of 1 g of a substance 1 o C For example: WATER VS. METAL -Higher the specific heat: the less fluctuation of heat and therefore the less fluctuation of the heat and therefore the less fluctuation of the temp. of the object. temp. of the object.WaterIron 4.18 J/(g x o C) 0.46 J/(g x o C) HighLow

28. Exothermic vs. Endothermic Exothermic: a process in which heat is released to the surrounding - The system loses heat as the surroundings heat up - q has a negative value because the system is losing heat Endothermic: a process in which the system gains heat as the surroundings cool down - Heat flows into a system - q has a positive value because the system is gaining heat

29. Calorimetry To measure specific heat capacity a bomb calorimeter is used. Calorimetry is based on the principle: Law of conservation of energy

30. Bomb Calorimeter Bomb Calorimeter

31. Plastic Cup Calorimeter Plastic Cup Calorimeter