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Matter & Energy

Matter & Energy. Ch.2. (2-1) Chemical E. E that exists in the bonds that hold atoms together When bonds are broken chemical E is released Digesting food. Energy. The capacity to do work SI unit : joule (J) Law of conservation of E : E is neither created nor destroyed

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Matter & Energy

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  1. Matter & Energy Ch.2

  2. (2-1) Chemical E • E that exists in the bonds that hold atoms together • When bonds are broken chemical E is released • Digesting food

  3. Energy • The capacity to do work • SI unit: joule (J) • Law of conservation of E: E is neither created nor destroyed • Einstein: If matter is destroyed, E is created. If E is destroyed, matter is created. So the total amt of mass and E is conserved.

  4. Mass & E Are Closely Related • E = mc2 • Relates how much E can be obtained from a given mass

  5. Types of E • Kinetic (KE): E in motion • The faster an object moves the more KE it has • Depends on mass and velocity • KE = ½ (mv2) • Potential (PE): E of position • Stored E

  6. E Can Be Transferred • Heat: sum total of KE of the particles in a sample of matter • System: all components that are being studied • Surroundings

  7. Temperature • Measure of the avg. KE of the particles in a sample of matter

  8. Temp. Scales • Kelvin(K) = ºC + 273.15 ºC • Absolute zero: lowest temp. theoretically • Celsius (ºC) = K – 273.15 K = (ºF – 32) x 5/9 • Fahrenheit (ºF) = (ºC x 9/5) + 32

  9. Specific Heat Capacity • (cp): amt. of heat E required to raise the temp. of 1 g of a substance by 1 K • Units: J/g•K • Calculated from experimental data

  10. (2-2) Scientific Method • Observe • Form hypothesis • Testable explanation of observations • If, then • Test • Controlled experiment • Theorize • Well-tested explanation of observations • Publish results

  11. Scientific Law • Description of the natural world that has proven reliable over time • Describes, doesn’t explain • Law of conservation of mass: mass is neither created nor destroyed

  12. (2-3) Measuring • Accuracy: how close it is to true value • Precision: how closely several measurements are to 1 another • Can be precise w/out being accurate

  13. Significant Figures • Any digit that’s known w/ certainty plus 1 final digit • Nonzero digits are always significant • See Table 2-3, p. 59

  14. Sigfig Rules for Zeros • B/w nonzero digits are - 40.7 has 3 sigfigs • In front of nonzero digits are not - 0.009587 has 4 sigfigs • At end of # and to right of decimal are - 85.00 has 4 sigfigs • At end of # with no decimal may or may not be • 2000 can have 1 to 4; 2000. has 4 sigfigs

  15. Exact Numbers • 2 types: • Count • 24 students in Chemistry • Conversion factor • 1000 mm in 1 m • Unlimited # of sigfigs (no uncertainty)

  16. Calculations • x & ÷: smallest # of sigfigs • + & -: smallest # to the right of decimal

  17. Calc. Practice • 12.257 x 1.162 = 14.2426234 • 4 sigfigs = 14.24 • 3.95 + 2.879 + 213.6 = 220.429 • 1 place = 220.4

  18. Scientific Notation • Used for very large or very small numbers • 1st part: # 1 to 10 • 2nd part: power of 10 • Ex: 0.000 000 000 000 005 = 5 x 10-15 • Ex: 1 000 000 000 = 1 x 109

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