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Measurement Class 2

Measurement Class 2. OB: What is density, how is it measured? What are the three temperature scales, how to convert temperatures from one scale to another. Some background info… MASS: The amount of “stuff” in something

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Measurement Class 2

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  1. Measurement Class 2 OB: What is density, how is it measured? What are the three temperature scales, how to convert temperatures from one scale to another

  2. Some background info… MASS: The amount of “stuff” in something VOLUME: The amount of space stuff takes up WEIGHT: The affect of GRAVITY on a mass Mass is a ______________________________ Weight ________________ depending upon ____________________________________ Density is the mathematical relationship between ____________ + ________________ The formula to learn is:

  3. Some background info… MASS: The amount of “stuff” in something VOLUME: The amount of space stuff takes up WEIGHT: The affect of GRAVITY on a mass Mass is a CONSTANT Weight VARIESdepending upon STRENGTH OF GRAVITY (what planet you’re on) Density is the mathematical relationship between MASS + VOLUME The formula to learn is: mV D =

  4. Units for density are most often: grams/centimeter cubed g/cm3 or grams/milliliter g/mL 1 cm3 = 1 mL, There is NO SUCH THING as an mL3 If you don’t GETThat, RAISE YOUR HAND AND ASK!

  5. 1. A cube or metal has a mass of 4540 grams and it is 10.0 cm per side. (V = s x s x s) Calculate the density of this metal. (you must, must write the formula for each problem!)

  6. 1. A cube or metal has a mass of 4540 grams and it is 10.0 cm per side. (V = s x s x s) Calculate the density of this metal. (you must, must write the formula for each problem!) mV D = = 4540 g 1000 cm3 D = 4.54 g/cm3

  7. 2. What metal is it? (how could you know this?)

  8. 2. What metal is it? (how could you know this?) You could have memorized the density tables from a chem book, or you could just look it up! It’s titanium, Ti.

  9. FIVE pennies together have a mass of 14.5 grams. Their total volume is 1.75 cm3. Calculate the density of the pennies.

  10. FIVE pennies together have a mass of 14.5 grams. Their total volume is 1.75 cm3. Calculate the density of the pennies. mV D = = 14.5 g1.75 cm3 D = 8.28 g/cm3

  11. 4. Assuming the pennies are made up of pure copper,what is your % Error?

  12. 4. Assuming the pennies are made up of pure copper, what is your % Error? MV – AVAV %E = 8.28 – 8.960 g/cm38.960 g/cm3 MV – AVAV = %E = %E = -7.59% 3SF

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  14. Is your measured value for density UNDER or OVER the actual measurement for the density of copper? How would you KNOW?

  15. Is your measured value for density UNDER or OVER the actual measurement for the density of copper? How would you KNOW? A Negativepercent error means YOUR measure is under the actual measurement. 7.59% means it was close, (~ 8%) but it was not perfect. It’s like getting about a 92% correct on a quiz.

  16. 6. A bar of metal is 27.73 g and has volume of 4.70 cm3. Is it gold?

  17. 6. A bar of metal is 27.73 g and has volume of 4.70 cm3. Is it gold? mV D = = 27.73 g4.70 cm3 D = 5.90 g.cm3 (3SF!) Is that the density of gold? Check NOW! No guessing.

  18. Temperature We will not use Fahrenheit (normal for you) temperature in chemistry class. We will use _______________ AKA _____________________ As well as ________________________ Water boils Water freezes ?

  19. Temperature We will not use Fahrenheit (normal for you) temperature in science class. We will use Centigrade AKA Celsius As well as KELVIN F • C • K Water boils 212°F 100°C 373K 32°F 0°C 273K Water freezes -273 C Absolute Zero O K

  20. Converting Kelvin to Centigrade Formula: K = C + 273 Calculate room temperature in Kelvin. It’s exactly 26.0°C today. (write the formula to calculate this)

  21. K = C + 273 K = 26.0 + 273 = 299 K NOT DEGREES, it’s just Kelvins! 3 SF!

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