Measurements

1. Measurements http://www.brainpop.com/science/matterandchemistry/measuringmatter/preview.weml

2. Measurement in Chemistry In chemistry we • do experiments • measure quantities • use numbers to report measurements

3. Metric System (SI) • Is a decimal system based on 10 • Used in most of the world • Used by scientists and hospitals * SI means System International

4. Units in the Metric System • length meter m • volume liter L • mass gram g • temperature Celsius °C

5. Metric Prefixes • Metric Units • The metric system has prefix modifiers that are multiples of 10.

6. Place Values of Metric Prefixes

7. Stating a Measurement In every measurement there is a • Number followed by a • Unit from a measuring device The number should also be as precise as the measurement!

8. Uncertainty in Measurement • Scientific measurements are reported so that every digit is certain except the last, which is estimated.

9. Some Tools for Measurement Which tool(s) would you use to measure: A. temperature B. volume C. time D. weight

10. Intensive vs. Extensive Properties • Intensive—independent of the amount of substance They do not depend on the amount of matter Color, Oder, Luster, Malleability, Conductivity, Hardness, Melting/ Freezing Point, Boling Point, and Density • Extensive—dependent upon the amount of substance They depend on the amount of matter present Mass, Weight, Volume, and Length

11. When we measure length we measure how long something is. You can measure the length of ANYTHING!

12. Standard units Millimeters (mm) Centimeters (cm) Meters (m) Kilometers (km)

13. Mass vs. Weight Can you hear me now? • Mass: Amount of Matter (grams, measured with a BALANCE) • Weight: Force exerted by the mass, only present with gravity (pounds, measured with a SCALE)

14. Tools for measuring Mass • The triple beam balance

15. How to use a triple beam balance • 1) Make sure that the balance scale is at zero. • 2) Place object on balance scale the larges and move the largest rider one notch at a time until the beam drops. Move the rider back one notch (make sure it lock in place) • 3) Move the next largest rider until the beam drops. Back it up one notch. • 4) Move the smallest rider until the beam swings equally above and below the zero mark. • 5) Add up all the numbers to find the mass!

16. What is Volume? • Volume is the measure of the capacity of a container. • It is the measure of how much a container of a particular shape will hold - liquids, dry substances, etc.

17. What’s the formula? The formula for finding the volume of a rectangle is …. L x W x H = Volume This means we take the length times the width, then multiply that by the height.

18. What causes the meniscus? A concave meniscus occurs when the molecules of the liquid attract those of the container. The glass attracts the water on the sides. Measuring Volume We will be using graduated cylinders to find the volume of liquids and other objects. Read the measurement based on the bottom of the meniscus or curve. When using a real cylinder, make sure you are eye-level with the level of the water. What is the volume of water in the cylinder? _____mL Top Image: http://www.tea.state.tx.us/student.assessment/resources/online/2006/grade8/science/images/20graphicaa.gifBottom Image: http://morrisonlabs.com/meniscus.htm

19. Measuring Liquid Volume What is the volume of water in each cylinder? Images created at http://www.standards.dfes.gov.uk/primaryframework/downloads/SWF/measuring_cylinder.swf A B C Pay attention to the scales for each cylinder.

20. Volume Displacement A solid displaces a matching volume of water when the solid is placed in water. 33 mL 25 mL

21. 9 cm 8 cm 10 cm We can measure the volume of irregular object using water displacement. Amount of H2O with object = ______About of H2O without object = ______Difference = Volume = ______ http://resources.edb.gov.hk/~s1sci/R_S1Science/sp/en/syllabus/unit14/new/testingmain1.htm Measuring Solid Volume We can measure the volume of regular object using the formula length x width x height. _____ X _____ X _____ = _____ Click here for an online activity about volume. Choose Lessons  Volume & Displacement

22. Density Density is defined as mass per unit volume. It is a measure of how tightly packed and how heavy the molecules are in an object. Density is the amount of matter within a certain volume.

23. Which one is more dense? Demonstration: People in a square How about this: Which square is more dense?

24. Which one is more dense? https://www.youtube.com/watch?v=ZhL68D9BPiw

25. water and ice have different densities Which one is more dense?

26. To find the density 1- Find the mass of the object 3- Divide Density = Mass g Volume c³ 2- Find the volume of the object ALWAYS REMEMBER UNITS!

27. Platinum Mercury Aluminum DENSITY - an important and useful physical property 13.6 g/cm3 21.5 g/cm3 2.7 g/cm3

28. DENSITY Brick Styrofoam • Density is anINTENSIVEproperty of matter. • does NOT depend on quantity of matter. • temperature • Contrast withEXTENSIVE • depends on quantity of matter. • mass and volume.

29. ProblemA piece of copper has a mass of 57.54 g. It is 9.36 cm long, 7.23 cm wide, and 0.95 mm thick. Calculate density (g/cm3).

30. If you have 2 or more substances, • the MORE dense substance will be on bottom • The LESS dense substance will be on top

31. Temperature • Particles are always moving. • When you heat water, the water molecules move faster. • When molecules move faster, the substance gets hotter. • When a substance gets hotter, its temperature goes up. LecturePLUS Timberlake

32. Temperatureis measured in degrees.

33. Temperature is measured on two scales: Celsius and Fahrenheit. 37 C 98.6 F

34. C We will use Celsius The lower case “C” is the symbol for the Celsius scale.