It’s Time to Start Cooking!

1. It’s Time to Start Cooking! Catalyst: • Open all handouts on the website. • Turn Chapter 1 homework in. • How many significant figures are in 0.5000 • (0.24567)(0.034) = ? (GIVE CORRECT SIG FIGS) • 4.5 + 0.01434 = ? (GIVE CORRECT SIG FIGS)

2. Lecture 0.3 – Sig Figs, Dimensional Analysis, and Cooking Protocol

3. Every Chef Needs Proper Tools • Just like chefs do in the kitchen, chemists use tools to take exact measurements of the substances they interact with. • Sometimes cooking can be an art, but chemistry is a science. • We want to be precise and accurate.

4. Precision and Accuracy • Precision – Measure of how close individual measurements agree with one another • A standard deviation tells someone how precise you were during a laboratory. • Accuracy – How close individual measurements agree with the “true” value.

5. Significant Figures • There is always uncertainty in the last digit of any quantity that we report. • Significant Figures – All digits of a measured quantity • The number of digit reported represent the number of significant figures a number has

6. Determining the Number of Sig Figs • The most important rule is that all nonzero digits in any measurement are significant: • Zeros between nonzero digits are always significant. For example, 1005 has ______ sig figs. • Zeros at the beginning of a number are never significant. For example, 0.005 has _____ sig fig. • Zeros at the end of a number are significant only if there is a decimal. For example, 3.0 has ____ sig figs, but 30 has _______ sig fig.

7. A Note on Scientific Notation • Recall that we can write a number like 10,300 in scientific notation as 1.03 x 104 • This number would have _____ sig figs

8. Sig Figs for Calculations • Determine sig figs only after a calculation is complete.

9. Sig Fig for Addition/Subtraction • When you add/subtract numbers, the answer has the same number of decimal places as the number with the least decimal places. Round off to one decimal place since 83.1 has the least number of decimal places! Final answer you report is 104.9

10. Sig Figs for Multiplication/Division • When you multiply or divide numbers, the answer has the same number of sig figs as the number with the fewest sig figs. 4 sig figs 2 sig figs, so the answer needs 2 sig figs 32 cm2

11. When does this translate to the kitchen? • Cooking is more of an art – often times the same dish will never be made using the exact same quantity of ingredients. • Baking, however, is much more like science. Exact quantities and ratios are necessary to ensure that desired product is achieved! • Why are precision/accuracy important here?

12. Kitchen Knowledge:Three Important Macromolecules • Food contains a large number of things, but these are the essential ones: • Carbohydrates • Lipids • Proteins

13. When I get in the kitchen, what do I eat? • Though they vary in caloric content, they are all essential to human life in specific ways. • A low-fat diet alone won’t help dieting citizens, as the hormone insulin is a key player in weight regulation, among others.

14. When I get in the kitchen, what do I eat? • It’s actually possible to estimate food content just by knowing a few easily identifiable facts.

15. Setting Up Conversion Factors • To make calculations like this, we have to use conversion factors. • We know that certain quantities are equal to one another. For example, we know that in fats: 1 gram = 9 calories • Just as we food, we know conversions for measurement: 1 in = 2.54 cm • For example convert 6 in to cm:

16. Table Talk • How many gallons of milk are in 1500 L? (1 gal = 3.79 L)

17. Two or More Step Conversions • Often times, you need to do multiple conversions in order to complete the desired conversion. • For these problems, you should plot out the units you will need to convert between to get to your final answer. Hours Minutes Seconds 1 hour = 60 minutes 1 minute = 60 seconds

18. Convert 3 hours to seconds 60 min 60 sec 3 hours 10,800 sec 1 hour 1 min

19. Class Example • You want to run to your favorite restaurant, but it’s 15.2 miles away! How many inches is this? (1 mi = 5280 ft and 1 ft = 12 in)

20. Table Talk • It takes you 15,250 s to slow-braise pork shoulder for carnitas. How many days did it take you to complete this?

21. Conversions and the Metric System • Recall, that the metric system is based on the power of 10. • These powers of 10 will convert you back to the base unit. Once you are at the base, you can convert to the desired unit.

22. Memorize these prefixes and conversion!

24. How to Remember the Order King Henry Died By Drinking Chocolate Milk

25. Converting is like a Staircase

26. Metric Conversion Example • You have 425 cg of enriched flour, how many kg do you have?

27. Sig. Fig Practice • Complete Problem Set 0.1 • Be sure to use the appropriate units!

28. Quiz

30. Closing Time • Have all supplies by Thursday/Friday • Quiz on Ch. 1 on Wednesday • Complete Pre-lab for Lab 0. MUST BE DONE BEFORE CLASS • Focus on metric system, sig figs,and dimensional analysis!