Science & Measurement A. The Nature of Science

1. Science & Measurement A. The Nature of Science * 1. Science is the totalcollection of knowledge gained by man’s observation of the physical universe. 2. Science tries to answer the questions howandwhat (not why).

2. B. Two main types of science 1. Pure science – attempts to gain new knowledge; discoveries; research. 2. Applied science (technology) is the use of science in practical ways.

3. C. Physical Science 1. Chemistry – study of matter and the changes it undergoes. 2. Physics – study of energy & motion.

4. D. Scientific Statements • Facts – observable and indisputable. • Data – information gained from experimentation. • Laws – statements that describe patterns in nature with no known exceptions. • Theories – explanations based on evidence (may be wrong). • Models – man-made ideas to help us visualize scientific concepts.

5. 3. Laws – statements that describe patterns in nature with no known exceptions. 4. Theories – explanations based on evidence (may be wrong). 5. Models – man-made ideas to help us visualize scientific concepts.

6. F. The Scientific Method 1. Identify the problem (in the form of a question). 2. Gather information by research. 3. Form a hypothesis (an educated guess). 4. Experimentation. 5. Analyze data & make conclusions. 6. Make predictions.

7. G. Scientific Experimentation 1. An experiment is a controlled test. 2. Only one variable should be changed at a time. a. Manipulated (independent) – changed by the experimenter. b. Responding (dependent) – the effect.

8. 3. Constants do not change. 4. Controlled variables are those which could change, but are not allowed to. 5. Two parts to an experiment: a. Control group – normal conditions. b. Experimental group(s) – variables are changed. 6. Prediction is the goal of experiments.

9. H. Types of Measurements • Length • a. The distance from one point to another point. • b. Base unit is the meter (m). • c. Tool is the metric ruler.

10. 2. Volume a. The amount of space a substance occupies. b. Base unit is the liter (L). c. Tools: metric ruler for regular solids or graduated cylinder for liquids. d. Objects can be regular (flat on all sides) or irregularly shaped.

11. Reading the Meniscus Always read volume from the bottom of themeniscus. The meniscus is the curved surface of a liquid in a narrow cylindrical container.

12. Try to avoid parallax errors. Parallaxerrorsarise when a meniscus or needle is viewed from an angle rather than from straight-on at eye level. Correct: Viewing the meniscusat eye level Incorrect: viewing the meniscusfrom an angle

13. Measuring Volume • Determine the volume contained in a graduated cylinder by reading the bottom of the meniscus at eye level. • Read the volume using allcertaindigits. • Certaindigits are determined from the calibration marks on the cylinder. • Theuncertaindigit (the last digit of the reading) is estimated. We will not use this.

14. Use the graduations to find all certain digits There are two unlabeled graduations below the meniscus, and each graduation represents 1 mL, so the certain digits of the reading are… 52 mL.

15. Estimate the uncertain digit and take a reading The meniscus is about eight tenths of the way to the next graduation, so the final digit in the reading is . 0.8 mL The volume in the graduated cylinder is 52.8 mL.

16. 10 mL Graduate What is the volume of liquid in the graduate? 6 6 _ . _ mL

17. 25mL graduated cylinder What is the volume of liquid in the graduate? 1 1 _ _ mL

18. 100mL graduated cylinder What is the volume of liquid in the graduate? 5 2 _ _mL

19. 3. Mass a. The amount of matter in a substance. b. Base unit - kilogram (kg). c. Tool is the balance.

20. Measuring Mass - The Beam Balance Our balances have 3 & 4 beams. Read it like money. Line up decimals to add final masses.

21. Balance Rules In order to protect the balances and ensure accurate results, a number of rules should be followed: • Always check that the balance is level and zeroed before using it. • Never weigh directly on the balance pan. Always use a piece of weighing paper to protect it. • Do not weigh hot or cold objects. • Clean up any spills around the balance immediately.

22. Mass and Significant Figures • Determine the mass by reading the riders on the beams at eye level. • Read the mass by usingall certaindigits.

23. Determining Mass 1. Place object on pan 2. Move riders along beam, starting with the largest, until the pointer is at the zero mark

24. Check to see that the balance scale is at zero

25. 1 1 4 ? ? _ _ _ . _ _ Read Mass

26. 1 1 4 4 9 _ _ _ . _ _ Read Mass More Closely

27. 4. Weight a. A measure of gravitational force on an object. b. Unit is the newton (N). c. Tool is the scale.

28. 5. Time a. How long an event takes to occur. b. Unit is the second (s). c. Tool is the clock (stopwatch).

29. 6. Temperature • The amount of kinetic energy a substance has. • SI unit is the Kelvin (K). • Tool is the thermometer.

30. The Thermometer • Determine the temperature by reading the scale on the thermometer at eye level. • Read the temperature by usingall certaindigits. • Certaindigits are determined from the calibration marks on the thermometer. • On most thermometers encountered in a general chemistry lab, the tenths place is the uncertain digit.

31. Do not allow the tip to touch the walls or the bottom of the flask. If the thermometer bulb touches the flask, the temperature of the glass will be measured instead of the temperature of the solution. Readings may be incorrect,particularly if the flask is on a hotplate or in an ice bath.

32. Reading the Thermometer Determine the readings as shown below on Celsius thermometers: 8 7 3 5 _ _ C _ _ C

33. 7. Density a. How compacted the matter is in a substance. b. Units can be g/mL, g/cm3, kg/m3. c. Density is a derived unit (it is made up of other types of measurement). d. D = m / v e. Objects float if their density is less than the density of the fluid they are in.

34. I. SI - International System of Units 1. Based on multiples of 10 2. Common metric prefixes: a. mega- (M) 1 000 000 x b. kilo- (k) 1 000 x c. hecto- (h) 100 x d. deka- (da) 10 x e. deci- (d) 0.1 x (1/10) f. centi- (c) 0.01 x (1/100) g. milli- (m) 0.001 x (1/1000) h. micro- (u) 0.000 000 001 x