Intro to Science, Measurements, Data Collections

Intro to Science How does Science happen? 1. Observation 2. Identify Problem 3. Investigation/Research 4. Formulate Hypothesis 5. Experimentation 6. Collect Data 7. Conclusion ◦Does this sound familiar?

Intro to Science Variables tested during experimentation ◦Independent Variable – the variable that is changed during an experiment ◦Dependent Variable – the variable that is dependent on the change in the experiment ◦Control Group – The group that receives no change to see what would happen naturally without experiment ◦Experiment Group – The group that receives the factors of experiment to test the change in results

It is possible to study the sciences and gain some appreciation and understanding of it without mathematics.

However, the depth of your comprehension of chemistry is directly related to your math skills. The topics we are about to review are essential math skills that you should master before studying chemistry. lt is critical that you seek tutoring at any time you do not understand a topic in this unit.

Intro to Science Mathematics can be used to measure many laws. ◦Quantitative measurements – Measurements that contain a numerical amount of evidence. ◦Qualitative measurements – Measurements that contain an observable amount of evidence. Tell which is which: 1.The apple is more red than the other. 2.The man is twice as fast as the dog. 3.The iron contains 1,500kJ less heat than the Aluminum.

Intro to Science In order to make the graphs and charts we need, we use numerical data. Metric System ◦System of organized, alike measurements that can be related to one another along a simple scale. SI Units ◦Formal units used for types of measurements in science. ◦Developed by the French!

Intro to Science Found on pg in your text

Intro to Science How do we get the best result from our measurements? Accuracy vs. Precision ◦Accuracy – A measurement that is close to the accepted value. ◦Precision – A set of measurement results that are consistent with one another

II. Kinds of numbers

Intro to Science In lab you measured the volume during 4 trials and got 23 cm 3, 26 cm 3, 21 cm 3, 22 cm 3 ◦If the accepted value should have been 25 cm 3, then were your measurements accurate? Were they precise? ◦What is a reason you might have gotten more than the accepted value?

Kinds of numbers II. Kinds of Numbers B. Counting numbers ◦1. numbers that you count (duh) a. are number without units b. are known exactly examples: you are holding 5 pens; there are 29 students in the class

Kinds of numbers 1. Defined numbers a. are numbers that somebody defined to be true b. are known exactly examples: 16 oz = 1 lb.; 2.54 cm = 1 in; 12 in = 1 ft

Kinds of numbers 3. Measured numbers a. are obtained with a measuring device ex: yard stick, balance b. measured numbers are not known exactly; there is a limit to how many digits you can obtain when measuring.

Kinds of numbers 4. Practice identifying numbers: a. What kind of number is “3 people”? counting b. What kind of number is 1 quart? defined

II. Kinds of numbers 4. Practice identifying numbers: While jogging to school this morning, you pass 3 people each drinking 1 quart of orange juice. counting (3 people) defined (1 quart)

MATH REVIEW I. Exponential notation or Scientific notation ◦1. lmportance: makes expressing very large and very small numbers easier

MATH REVIEW 2. Standard Scientific Notation: a. has only one number in front of a decimal point [or an understood decimal point] b. converting to standard notation

MATH REVIEW Report the following numbers in scientific notation: a. 20,000 b c X X X 10 -6

What are Significant Digits? III. Significant digits (sig figs) A. Significant digits are all digits that are known with some degree of accuracy

What are Significant Digits? 1. Counting numbers and defined numbers have an infinite number of significant digits because they involve no doubt a. there are 29 people in the class b. there are 12 inches in a foot

What are Significant Digits? B. Identifying Significant Digits 1. all non zero numbers are significant 2. middle zeros are significant (sandwich rule)

III. What are Significant Digits? 3. leading zeros are never significant a. they are important but not significant (measured) b. leading zeros are only place holders

III. What are Significant Digits? 4. trailing zeros are significant if there is a decimal point a. If a number is expressed in scientific notation, the zeroes are removed without affecting the value of the number

III. What are Significant Digits? All of the following measurements have 3 significant digits. 245 m 18.0 g 308 km g Which of the rules explains why these numbers all have 3 significant digits?

III. What are Significant Digits? C. Calculations Using Significant Digits 1. Rounding a. look one place past the last sig fig b. if it is five or more round up c. if it is less than five do not round

What are Significant Digits? Self Test Round the following numbers to three significant digits, then to one m x 10 8 m m 9009 m x m m 87.1 m 4.36x10 8 m m 9010 m 1.78x10 -3 m 630. m 90 m 4x10 8 m 0.02 m 9000 m 2x10 -3 m 600 m

III. What are Significant Digits? 2. Adding & Subtracting: round answers to the least number of places after the decimal in the numbers you are adding or subtracting

III. What are Significant Digits? Example If you were adding : _____________ The calculator answer would be However, the answer would be correctly reported as because 25.3 only has one place beyond the decimal, meaning it was the least precise of the measurements.

What are Significant Digits? Self Test: a. 61.2m m + 8.6m 79.2m b. 9.44m m 7.33m c. 1.36m m 11.53m d m m 17.3m

III. What are Significant Digits? Solutions: a. 79.2m b. 7.33m c m d. 17.3m

III. What are Significant Digits? 3. Multiplying & Dividing: round answers to the least number of significant diqits in any of the numbers you are multiplying or dividing

III. What are Significant Digits? Example If you were multiplying: 25.3 X The calculator answer would be However, the answer would be correctly reported as 3130 or 3.13 X 10 3 because 25.3 only has 3 significant digits

III. What are Significant Digits? Self Test: a. 8.3m x 1.22m b. (1 x m) (2.9 x m) c. 8432m ÷12.5m d. 5.3m ÷ 0.255m

III. What are Significant Digits? Solutions: a. 10. m 2 b. 3 x 10 5 m 2 c. 675 m d. 21 m

IV. Your Calculator A. Getting to know your calculator 1. the most important button you’ve never used, the EE or Exp button

IV. Your Calculator A. Getting to know your calculator 2. the “EE” or “Exp” button basically is shorthand for the words “times ten to the…” so it should be used as such when entering data into your calculator Important note: Sometimes the “EE” button is on the second row of command buttons

III. What are Significant Digits? Example If you were multiplying: (25.3 x 10 3 )X( x10 -6 ) You would enter “25.3” then “EE” then “3” then “X” then “ ” then “EE” then “-6” then “=“. The calculator answer should be (Of course, the answer would be correctly reported as 3.13 because 25.3 only has 3 significant digits)

III. What are Significant Digits? Self Test Perform the following calculations and report the answer with the appropriate number of sig figs. (1) X x 10 8 (2) X x (3) 9009 x X x 10 8

III. What are Significant Digits? Self Test answers (1) x (2) x (3) x