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# The Nature of Science and Technology Chapter 2

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### The Nature of Science and Technology Chapter 2

1. 1. The Nature of Science and Technology Chapter 2 – Section 1
2. 2. • Measurement – A Common Language – A Standard Measurement System • Metric System • International System of Units (SI) – Length • Units of Length • Measuring Length – Mass • Units of Mass • Measuring Mass • Difference Between Mass and Weight – Volume • Volume of Liquids, Solids, Irregular Solids – Density • Units of Density • Densities of Common Substances – Time • Units of Time • Measuring Time – Temperature • Units of Temperature • Measuring Temperature
3. 3. Key Concepts • Why do scientists use a standard measurement system? • What are the SI Units of measure for length, mass, volume, density, time, and temperature? • How are conversion factors useful?
4. 4. Standard Measurement System • Metric System – Developed in France (1790s) – Universal system called the Metric System – System of Measurement based on the number 10
5. 5. Standard Measurement System • International System of Units (SI) – Version of metric system used by modern scientists – Scientists use SI units to measure length, volume, mass, density, temperature, and time – Standard system of measurement allows scientists to compare data and communicate with each other about their results
6. 6. SI Units • Based on multiples of 10 • Each unit is 10 times larger than the next smallest unit and one tenth (1/10) the size of the next largest unit • Refer to Figure 1 – Pg 45
7. 7. Length • Units of Length – Distance from one point to another – The basic unit of length in the SI system is the meter (m). – To measure smaller objects, use centimeter (cm) or millimeter (mm)
8. 8. Length • Measuring Length – Tools – Metric ruler • Centimeter markings
9. 9. Mass • Mass is a measure of the amount of matter an object contains. • Units of Mass – The basic unit of mass in the SI system is the kilogram (kg). – To measure the mass of smaller objects, use gram (g) as the unit
10. 10. Mass • Measuring Mass – Balance • Triple Beam Balance – Appendix C for directions
11. 11. Mass • Difference Between Mass and Weight • Weight is a measure of the force of gravity acting on an object
12. 12. • Mass is a measure of the amount of matter an object contains. • Weight is a measure of the force of gravity acting on an object
13. 13. Learning Check • What is the basic unit of length in the SI system? • What is mass? • What is the basic unit of mass in the SI system?
14. 14. Volume • Volume is the amount of space an object takes up. • Volume of Liquids – To measure the volume of a liquid, use a unit known as the liter (L) – For smaller volumes use milliliters (mL)
15. 15. Volume • Volume of Rectangular Solids – Volume of a solid object, use cubic centimeter (cm3) – For solids with larger volumes, scientists use the SI unit known as the cubic meter (m3) – Volume = Length x Width x Height – Example: 20cm x 6cm x 25cm = 3000 cm 3
16. 16. Volume • To calculate volume… (pg 50 and 51) – Multiply the numbers – Multiply the units – ***Make sure you use the same units for all measurements when calculating the volume of a regular solid***
17. 17. Volume • Volume of Irregular Solids • Can you measure length? Width? Or Height??? • Instead… try immersing the object in water – Water level will rise – Displacement of volume can be determined
18. 18. Vocabulary: Meniscus • The curved upper surface of a liquid in a column of liquid • Draw picture
19. 19. Density • The measure of how much mass is contained in a given volume • Density = Mass/Volume
20. 20. Density • Units of Density – Density is made up of two other measurements • Mass • Volume – An object’s density is expressed as a combination of two units. – Example: grams per cubic centimeter – Example: grams per milliliter (g/mL)
21. 21. Densities of Common Substances • Figure 6 – Pg 53
22. 22. Time • Units of Time • The second (s) is the SI unit used to measure time.
23. 23. Time • Measuring Time – Clocks – Watches • Look at conversions for time (pg 53)
24. 24. Temperature • Units of Temperature (pg 54) – Celsius temperature scale – Water freezes at 0 degrees Celsius – Water boils at 100 degrees Celsius – Human body temperature is 37 degrees Celcius – Kelvin scale (K) is the official SI unit for temperature
25. 25. Temperature • Measuring Temperature – Thermometer
26. 26. Converting Between Units • Need to know conversion factor • A conversion factor is an equation that shows how two units of measurement are related
27. 27. Converting Between Units (pg 55) • Write down the measurement you want to convert • Find conversion factor that relates the two units you are converting • Write conversion factor as a fraction (include units) • Multiply the measurement you are converting from by the fraction – Units will cancel out with the units in the denominator of fraction
28. 28. Chapter 2: Section 2 Mathematics and Science
29. 29. Estimation • An estimation is an approximation of a number based on reasonable assumptions • Scientists rely on estimates when they cannot obtain exact numbers • Not the same as guessing because an estimate is based on known information!
30. 30. Accuracy • Refers to how close a measurement is to the true or accepted value
31. 31. Precision • Refers to how close a group of measurements are to each other
32. 32. Accuracy and Precision in Measurements • Both accuracy and precision are important when you make measurements • See Figure 11 – pg 62
33. 33. Significant Figures • The digits included in a measurement • Include all of the digits that have been measured exactly, plus one digit whose value has been estimated
34. 34. Significant Figures • Adding and Subtracting – The answer can only have as many figures after the decimal point as the measurement with the fewest figures after the decimal
35. 35. Percent Error • Percent error calculations are used to determine how accurate, or close to the true value, an experimental value really is
36. 36. • Percent error = Difference between experimental value and true value/True value x 100%
37. 37. • A low percent error means that the result you obtained was very accurate • A high percent error means that your result was not very accurate
38. 38. Mean, Median, and Mode • Mean – Add up all numbers and divide by the number of data added up • Median – Middle number in a row of numbers (lowest to highest) • Mode – Numbers that appears the most in a given set of data