Presentation on theme: "What is Science? -the organized body of knowledge about the Universe derived from observation and experimentation carried out to determine the principals."— Presentation transcript:
What is Science? -the organized body of knowledge about the Universe derived from observation and experimentation carried out to determine the principals underlying what is being studied
Scientific Method Question why or how something happens Research Existing Data Form a hypothesis (expected answer) Experiment Collect data (information) Draw a conclusion Contemplate opportunities for future study
DATA Data must be collected to support or refute the hypothesis: Data may be Quantitative:Numeric Quantity (measurements, etc..) Qualitative: Narrative description
The Scientific Method allows science to be universal. Why? Language Barriers exists between countries (English Speakers vs. Non- English Speakers) Measurement Standards (ex. distance can be measured in feet or meters) SI Units “Kms”(Mass: Kilogram, Distance: Meter, Time: Second) This standardization allows for scientists around the world to share ideas.
Setting up a valid experiment: Scientific Method Style Make an observation: Plants seem to grow best with a certain amount of moisture. State the question: How does water affect the growth of plants? Form a hypothesis: If I give a plant more water, then it will grow taller. Set up the experiment: One control group and one experimental group. Collect data: Record plant growth and water distribution and graph the data. Repeat: Redo the experiment to disprove results.
Variables in an experiment Independent variable: the portion of the experiment that the scientist actually controls or changes (the cause / the if) -always graphed on the x axis Dependent variable: the portion of the experiment that changes on its own (the effect / the then) – always graphed on the y axis Dependent Variable Independent Variable Y axis X axis
Control Group Full sun and 25*C Experimental Group Full sun and 25*C A BCD Plant water added daily growth A 10mL 0 cm B 15mL 5 cm C 20mL 10 cm D 25 mL15cm
Growth (cm) Water added (mL) 0 5 10 15 20 25 15 10 5 0 Growth vs. Water for Plants A graph of this shape supports the hypothesis that more water increases plant growth.
Growth (cm) Water added (mL) 0 5 10 15 20 25 15 10 5 0 Growth vs. Water for Plants A graph of this shape does not support the hypothesis that more water increases plant growth. You may have over-watered the plant and it wilted.
Scientific Theory vs. Law A scientific law is simply an observation about nature: Ex: What goes up, must come down”A scientific law is simply an observation about nature: Ex: What goes up, must come down” A scientific theory is an explanation of an observation. Ex. “The bending of space causes gravitation”A scientific theory is an explanation of an observation. Ex. “The bending of space causes gravitation” Theories are:Theories are: -Simple and clear -Testable-Repeatable
Relationship of Science and Technology Wheel of knowledge:
Significant Figures the number of digits in a measurement that are known with certainty ___________________________________ 4 Rules for finding significant figures Rules for Adding / Subtracting Sig Figs Rules for Multiplying / Dividing Sig Figs
Rule 1 for determining Significant Digits All non-zero numbers are significant 1.27m has 3 sig figs 2278s has 4 sig figs 98 feet has 2 sig figs
Rule 2 for determining Significant Digits Any zero that is between two non-zero numbers is significant. 105m has 3 sig figs 190003cm has 6 sig figs 2006 mi has 4 sig figs
Rule 3 for determining Significant Digits Any zero to the right of a decimal is significant. 23.30s has 4 sig figs 0.450m has 3 sig figs 29.000m has 5 sig figs
Rule 4 for determining Significant Digits A zero that has the sole purpose of placing a decimal is not significant. 20 m has 1 sig fig 200 mi has 1 sig fig 0.0092 m has 2 sig figs
Addition and Subtraction for Significant Digits With addition and subtraction, limit your answer to the number of decimal places held by the measurement containing the least number of decimal places. 2.50cm + 9.0 cm = 11.5 cm (not 11.50 cm) 1/100 Decimal Place 1/10 Decimal Place 1/10 Decimal Place
35.05g - 5.0g = 30.05g =30.1g 1/100 Decimal Place 1/10 Decimal Place 1/10 Decimal Place Rounding: 0-4 = Round down 5-9 =Round up
Multiplication and Division for Significant Digits When multiplying or dividing measurements, your answer should contain the same of significant digts found in the measurement with the least number of significant digits. 3.0 cm X 2 cm = 6 cm 2 (not 6.0 cm 2 ) 2 sig figs 1 sig fig
50.00 g / 2 moles = 25 g/mole = 30 g/mole 4 sig figs 1 sig fig 2 sig figs Answer must also have 1 sig fig
Scientific Notation A way to express very large or small numbers. Formula: Z X 10 n Z is the mantissa. It is a number between 1 and 10. The number of significant figures is included in the mantissa. n is a power of 10 that represents the direction and number of spaces that the decimal is moved in order to arrive at the Z number. Positive n moves the decimal to the right. Negative n moves the decimal to the left.
Example Convert 207,000 to scientific notation. 2.07 X 10 5 Convert 0.00101 to scientific notation. 1.01 X 10 -3 1.) write down all sig figs 2.) place decimal so the number is between 1 and 10 3.) count placeholders and record them as an exponent
Working with S-N Adding/Subtracting Numbers in S-N Be sure all factors have same power of 10 (adjust 1 if needed) Add/Subtract Mantissa Exponent stays the same Adjust for correct number of decimal places Multiplying/Dividing Numbers in S-N Multiply/Divide Mantissa Add/Subtract exponent Adjust/round for correct sig figs. Example: 2.07 X 10 5 + 1.01 X 10 4 2.07 X 10 5 x 1.01 X 10 4
Accuracy vs. Precision Accuracy –The closeness of a measurement to an accepted value. Precision –The closeness of a group of measurements to each other. 2 of 3 are accurate. Accurate?No. Very precise. 3 are grouped together.
Precision How do you express the precision of a measurement tool? Precision is expressed as + or – the smallest unit on the instrument. EX. A standard metric meter stick has millimeters as its smallest increment of measure. The precision is as expressed as + or -1mm.
Measurements The SI System (International System) –Based on the metric system, the powers of 10, and uses prefixes. –World-wide use. –Also known as the KMS system. Kilogram, meter, second –Mass will be measured in kilograms with a triple beam balance. –Length will be measured in meters using a ruler. –Time will be measured in seconds using a stopwatch.
SI Base Units QuantityUnit TimeSecond (s) Length/DistanceMeter (m) MassKilogram (Kg) TemperatureKelvin (K) Amount of SubstanceMole (mol) Electric CurrentAmpere (A) Luminous IntensityCandela (cd)
Prefixes for the Metric System kilo hecto deca base deci centi milli 1.1.01.001 10 100 1000 1.) Move up or down depending upon conversion of units. 2.) Count steps each way. 3.) k, h, da, d, c, m Base units: gram, liter, meter, second
Conversion Example: Convert 256 cm to meters. meter decimeter centimeter millimeter 1.Start on centimeter 2.Count steps to meter. 3.Move the decimal 2 places to the left. 4.) 2.56 m
Percent Error How far your measurements are away from an accepted value. You generally want 10% error or less. This would be equivalent to making a 90 on a test. Formula: % Error = | observed value – accepted value| X 100% accepted value
Percent Error Example The actual density of steel is 7.8 g/cc. In lab you measure the density as 9.2 g/cc. What is the percent error of your measurement? % error = | 9.2 g/cc – 7.8 g/cc | = 0.179 7.8 g/cc Convert this number to a % by multiplying it by 100. 0.179 X 100 = 17.9 % = 18 % Follow sig fig rules to round.