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1 Measurement in Chemistry In chemistry we  do experiments  measure quantities  use numbers to report measurements

2 Measurement You are making a measurement when you  Check you weight  Read your watch  Take your temperature  Weigh a cantaloupe What kinds of measurements did you make today?

3 Standards of Measurement When we measure, we use a measuring tool to compare some dimension of an object to a standard.

4 Some Tools for Measurement

5 Learning Check M1 From the previous slide, state the tool (s) you would use to measure A. temperature____________________ B. volume ____________________ ____________________ C. time____________________ D. weight____________________

6 Solution M1 From the previous slide, state the tool (s) you would use to measure A. temperature_thermometer B. volume measuring cup graduated cylinder C. time_watch D. weight scale

7 Stating a Measurement In a measurement there is a  Number and a  Unit from measuring device

8 Learning Check M2 What is the unit of measurement in each of the following examples? A. The patient’s temperature is 102°F. B. The sack holds 5 lbs of potatoes. C. It is 8 miles from your house to school. D. The bottle holds 2 L of orange soda.

9 Solution M2 A. °F (degrees Fahrenheit) B. lbs (pounds) C. miles D. L (liters)

10 Exact Numbers Do not involve a measuring tool Are obtained when you count objects 4 tennis rackets 1 watch 2 pizzas Or use a definition 1 foot = 12 inches 1 meters = 100 cm

11 Learning Check M3 Classify each of the following as an exact (1) or a measured(2) number. A. ___Gold melts at 1947°F B. ___1 yard = 3 feet C. ___A red blood cell is 6 x 10 -4 cm in diameter D. ___There were 6 hats on the shelf E. ___A can of soda contains 355 mL of soda

12 Solution M3 Classify each of the following as an exact (1) or a measured(2) number. Give reason. A. 2 Requires a thermometer(measuring tool) B. 1 From a definition in English system C. 2_ Need measuring tool to determine D. 1_ Counted the hats (no measuring tool E. 2 Measured

13 Worksheet M1: Types of Numbers Obtain the worksheet and a metric ruler. Work together in groups of 3-4 students. Complete the data. Compare your measurements with another group of students. Complete the questions.

14 Accuracy Is how close a measurement is to the actual or true value good accuracy true value poor accuracy true value

15 Precision How well several measurements agree with each other good precision poor precision

16 Accuracy and Precision What can you say about the accuracy and precision in each of the following: Good precision, poor accuracy Good precision, good accuracy

17 In your new job, you are to make the pizzas the size shown above. Your first four pizzas are shown below. What can you say about the accuracy and precision of your pizzas?

18 Pizza Precision You have very good precision, but poor accuracy. I think the customers will want the pizzas made larger.

19 What can you say about the accuracy and precision of the next four pizzas? The next four pizzas.

20 Accuracy is improving. The two pizzas in the center show good accuracy. However, the precision is poor.

21 Match the following terms 1) Precision2) Accuracy ___ Is how close a measurement is to the true value. ___ Is how close several measurements are to each other. Can you have data that are precise, but not accurate? Why or why not? Learning Check M4

22 Match the following terms 1) Accuracy2) Precision _1_ Is how close a measurement is to the true value. _2_ Is how close several measurements are to each other. Yes. Data can be precise, but not close to the true value. Solution M4

23 Learning Check M5 How will each of the following affect accuracy and precision? 1. A meter stick that is missing the first centimeter. 2. A scale that has a zero point that is really five pounds above zero.

24 Solution M5 How will each of the following affect accuracy and precision? 1. The cut off meter stick will produce measurements that have poor accuracy, but good precision is possible. 2. The poorly calibrated scale will give a weight that is not accurate, but good precision is possible.

25 Learning Check M6 True(1) or false (2). Measurements can have poor accuracy and poor precision good accuracy and poor precision poor accuracy and good precision good accuracy and good precision

26 Solution M6 True or false. Measurements can have poor accuracy and poor precision good accuracy and poor precision poor accuracy and good precision good accuracy and good precision 1 1 1 2

27 True(1) or False(2) 1. ___All measuring tools have limitations 2. ___Some measurements can be exact 3. ___Every measurement has some error 4. ___Every measurement has uncertainty Learning Check M7

28 True(1) or False(2) 1. _1_All measuring tools have limitations 2. _2_Some measurements can be exact 3. _1_Every measurement has some error 4. _1_Every measurement has uncertainty Solution M7

29 Learning Check M8 A. Exact numbers are obtained by 1. measuring 2. counting 3. definition B. Measured numbers are obtained by 1. measuring 2. counting 3. definition

30 Solution M8 A. Exact numbers are obtained by 2. counting 3. definition B. Measured numbers are obtained by 1. Using a measuring tool

31 Worksheet M2: M&M’s Statistics Obtain the M&M’s Statistics worksheets and a package of M&M’s for your group. 1) Part 1. Predict the items requested, then open the package and determine the actual number. 2) Complete the data requested in Part 1. 3) Keep the paper and Part 2 for calculations at a later time.

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