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Chemistry, Matter and Measurements

Chemistry, Matter and Measurements. L. What is Chemistry?. AKA the central science The study of matter and the changes that it undergoes Used in everything!. What’s it matter?. Matter – anything that has mass and volume Mass – amount of matter Volume – space it takes up

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Chemistry, Matter and Measurements

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  1. Chemistry, Matter and Measurements L

  2. What is Chemistry? • AKA the central science • The study of matter and the changes that it undergoes • Used in everything!

  3. What’s it matter? • Matter – anything that has mass and volume • Mass – amount of matter • Volume – space it takes up • DON’T confuse mass with weight • Weight – gravitational pull on a mass • If I put you on the moon you weight less, however you have the same mass • If I cut your arm off you have less mass and weight……(and blood pressure)

  4. Macro vs Micro • Much of what happens in chemistry is on the macroscopic level • What you can see, touch, smell etc. • However , a lot happens on the submicroscopic level • To be seen we must make models • Model – a visual, verbal or mathematical explanation of data (turning Micro  Macro)

  5. Base Units • Use international system of units (SI) • Manipulated by powers of 10 Big ones for Chem.

  6. Derived Units • Taken by manipulating base units • Volume – space an object occupies • L (m) x W (m) x H (m) • Therefore, volume = m3 • 10 cm3 = 1 Liter (L) • Typical units: • Liters • cm3

  7. Derived Units (continued) • Density • Amount of mass packed into a volume • Density = Mass over volume (D = M/V) • Typical units are g/cm3

  8. More or less

  9. What’s Scientific Notation? My brain is on fire with the crazy amount of info here

  10. Rules of Sci. Not. • Always between 1 and 10 and ten raised to a power. • The power tells you how may times to multiply the 1st number by 10. • Ex: • 1.12 x 105 = 112,000 • 9.167324 x 102 = 916.7324 • works the same in the opposite direction. • Ex: • 4.5 x 10-4 = 0.00045 • 9.9999 x 10-20 = 0.000000000000000000099999

  11. Adding/Subtracting Sci. Not. • Get all exponents to the same value, then add/subtract the first number. • Ex: • 5 x 10-5m + 2 x 10-5m • 1.26 x 104kg + 2.5 x 103kg • 4.39 x 105kg – 2.8 x 104kg

  12. Multiplying/dividing Sci. Not. • 1st multiply/divide the first number • 2nd add (multiplication)/subtract (division) the second number • Ex: • (9 x 108)/(3 x 10-4) = (9/3) x 10(8 - -4) • (2 x 103) x (3 x 102) = (2 x 3) x 10(3 + 2)

  13. Practice • Pg 32 14a-h • Pg33 15a-d, 16a-d

  14. Significant figures • Include all known digits plus one estimated digit • Rules

  15. Measurement Reliability • Accuracy – how close a value is to an accepted value • Precision – how close a series of measurements are to one another.

  16. Ex: Students were asked to find the density of an unknown powder. The powder was table sugar which has a density of 1.59g/cm3 Which student was most precise? Which student was most accurate?

  17. Percent Error • Error -- Difference between experimental and accepted values • Percent error = (expected - actual)/accepted value x 100

  18. Ex: • Find the % error for student A trial 1

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