Thinking Scientifically “Insanity is doing the same thing over and over expecting different results” ~Einstein

The Scientific Method State the Problem Gather Information State your Hypothesis Test your Hypothesis Observe and Collect Data Draw Conclusions

Making Observations There are two types of observations: 1.A qualitative observation does not involve a number.  The sky is blue.  Water is a liquid. 2.A quantitative observation (also called a measurement) involves both a number and a unit.  Water boils at a temperature of 100. °C.  The book has a mass of 2.04 kg.

Steps to Thinking Scientifically Forming Hypotheses. ◦ A hypothesis in a possible explanation for an observation. Performing experiments. ◦ An experiment is carried out to test a hypothesis.  This involves gathering new information that enables a scientist to decide whether the hypothesis is valid – that is, whether it is supported by the new information learned from the experiment. Experiments always produce new observations, and this brings the process back to the beginning again.

Scientific Models Theory – an attempted interpretation, or a possible explanation of why nature behaves in a particular way. Law – A tried and tested explanation of nature that has been observed to be true, or a summary of what always happens.  The point of scientific experimentation is to test theories and shape them into laws that are truths about nature.

Units of Measure The SI System ◦ Scientists measure using a universal system called the International System. SI Units Physical QuantityNameAbbr Masskilogramkg Lengthmeterm Timeseconds TemperaturekelvinK Electric CurrentampereA Amount of Substancemolemol Luminous Intensitycandelacd

Scientific Notation Scientists often consider numbers that are inconvenient to write out or type into a calculator. ◦ Think of the grains of sand on a beach… ◦ Think of how many meters to the moon… We use scientific notation because we need it.

Practice: Scientific Notation Express the following numbers in scientific notation: ◦ 238,000  2.38 x 10 5 ◦ 1,500,000  1.5 x 10 6 ◦ 357  3.57 x 10 2

Practice: Scientific Notation Express the following numbers in scientific notation: ◦  4.3 x ◦  8.9 x ◦  4.3 x Practice

Prefixes Used in the SI System

Significant Figures Resistance is Futile! ; )

What is a significant figure? AKA “sigfigs” A significant figure is a number that matters in a calculation. All scientific calculations must consider significance. In science, answers are not considered entirely correct unless the correct number of significant figures are used. How much is regular gas?

Why is this so important? Significant figures represent the numbers in a final calculation that are known to be true without error. ◦ Some numbers come from measurements. ALL measurements made are inaccurate and contain some degree of error. Significant figures account for this error. Basically your answer cannot be more precise or more accurate than the tool used to make the measurement.

The Rules of Significance All nonzero integers are significant. Leading Zeros are not significant. Captive Zeros are significant. Trailing Zeros are not significant unless there is a decimal point. Exact numbers are infinitely significant. ◦ Known numbers (not measured) ◦ Counted numbers ◦ Definitions

Count the Sigfigs! How many sigfigs are in each of the following measurements? ◦ A sample of orange juice contains g of vitamin C. ◦ A forensic chemist in a crime lab weighs a single hair and records its mass as g. ◦ The distance between two points was found to be x 10 3 ft. ◦ In yesterday’s bicycle race, 110 riders started but only 60 riders finished.

Count the Sigfigs! How many sigfigs are in each of the following measurements? ◦ m ◦ x 10 2 L ◦ 480 Corvettes ◦ 1,200 ft 2 ◦ 200. kg

Rounding and Sigfigs…  In general for rounding… ◦ If the number following the last sigfig in the answer is greater than or equal to 5, round it up. ◦ If the number following the last sigfig in the answer is less than 5, it does not round up. DO NOT ROUND ANY ANSWERS UNTIL YOUR FINAL STEP IN THE CALCULATION!!!!!!!!!! ◦ Helpful Hint: Learn how to use the store and recall buttons on your calculators.

Rounding Practice Round each of the following to 2 significant figures: ◦ ◦ 433 ◦ 658,493 ◦ 50,098 ◦ 5.96 x 10 3 ◦ ◦ x 10 -4

Significance in Calculations Multiplication & Division ◦ The number of sigfigs in the result will have the same number of sigfigs as the LEAST precise measurement used in the calculation. Addition & Subtraction ◦ The result will have the same number of decimal places as the least precise measurement used in the calculation.

Practice: Sigfigs in Calculations Give each answer with the correct number of sigfigs: ◦ = ◦ 1081 – 7.25 = ◦ 2.3 * 3.14 = ◦ / 1.50 = ◦ – 73.9 = ◦ – ( ) = ◦ (2.68 – 3.2) / ( ) =

Practice: Sigfigs in Calculations Give each answer with the correct number of sigfigs: ◦ 5.18 * = ◦ (3.60 * 10-3) * (8.123) / 4.3 = ◦ = ◦ – 0.33 = ◦ (1.33 * 2.8) = ◦ 12.6 * 0.53 = ◦ (12.6 * 0.53) – 4.59 = ◦ (25.36 – 4.15) / =