1. Significant Figures

6. 6.For values in scientific notation, only digits in the coefficient (base #) are significant 1.20 x 10 21 ________ 5.00 x 10 -15 ______ 6.02 x 10 23 ______ Add this 6 th Rule to your notes about Scientific Notation!

7. When Rounding Significant Figures: Determine how many significant figures you HAVE? How many do you WANT? Circle the significant figure you will be rounding. Underline the sig fig right after it. 0 – 4 = stays the SAME and 5 - 9 = rounding UP. Example: Round 25.052 to 3 significant figures HAVE? = 5 WANT? = 3 Circle the sig figs you will round Underline the sig fig after it Round: in this case, the 5 rounds the 0 up to a 1. New answer = 25.1

9. Complete the rest of page 17-18 for homework!!! Multiplication and Division: 1. Determine the number with the FEWEST number of SIG FIGS in the problem 2. Round your answer to that number of sig figs. Addition and Subtraction: 1. Determine the number with the fewest number of decimal places (or the number with the largest smallest place value as a sig fig). 2. Round your answer to that number of decimal places.

10. Turn to Page 19 and prepare to take notes. Please pick up a calculator.

11. What we know so far… Low Motion = Low Temperature High Motion = High Temperature

12. Motion requires Energy (Kinetic) Higher Energy = Higher Temp. USUALLY energy is supplied by heat.

13. Law of Conservation: Heat loss or gain = Energy loss or gain Heat lost from hand = Heat gained by ice

14. Specific Heat is the amount of heat needed to increase the temperature of 1g of a substance by exactly 1 o C

15. By how much will the temperature of an object increase or decrease by gaining or losing heat energy? This is given by Specific Heat! Which substance has a greater specific heat? This means it takes longer to gain or lose heat!!

16. Specific Heat = c p q = mc p ΔT OR c p =__q__ m(ΔT)

17. q = mc p ΔT q = heat in joules (J) or calories (cal) c p = specific heat (J/g o C or cal/g o C) m = mass in grams (g) ΔT = change in temperature ( o C) ΔT = (T f -T i )

18. Now let’s try a problem… Look at the bottom of page 18 in your packet.

19. How much energy is required to raise a 34.0g sample of copper metal from 20.0 °C to 45.0 °C? The specific heat of copper is 0.385 J/g°C. Given: Unknown: C p m ΔT Equation: q = mc p ΔT

20. How much heat is released when a 3.20g sample of water is cooled from 83.0 °C to 54.0 °C? The specific heat of copper is 4.18 J/g°C. Given: Unknown: C p m ΔT Equation: q = mc p ΔT

21. Given: Unknown: C p m ΔT Equation: q = mc p ΔT

22. Now let’s try a problem…

24. SUBSTANCE Specific Heat (J/g °C) (J/g °C) Specific Heat (cal/g°C ) Copper0.380.09 Gold0.130.03 Water4.181.00 Mercury0.1400.033 You heat an unknown substance. If ΔT = 10.0 °C, m = 22 g, and q = 7.3 cal What is the identity of the material? Warm-up (9/22):

25. Warm-up: 9/23 1.32g of Hydrogen is mixed with 256 g of Oxygen to form water. The two reactants react completely (no reactants are left over). What is the mass of water that was produced? *You will need a laptop today.*

26. Park Bench Activity You will pick three materials that you think would make a good park bench. Once you have chosen three materials, you will research each of them to determine which would make the best bench. Record your work on the p23.