PowerPoint 3: Experimental Design/Calculations without Calculator

Scientific Method 1. Identify the Problem 2. Research 3. State the Hypothesis If _______, then __________. If _______, then __________. 4. Design/Perform Experiment 5. Collect and Analyze Data 6. State a Conclusion 7. Repeat

Repetition increases accuracy! It makes the results more valid!!

Parts of a Well Designed Experiment Control Group: Group under normal conditions Control Group: Group under normal conditions Experimental Group: Group that contains the change (IV) Experimental Group: Group that contains the change (IV)

Variables Independent Variable: What the experimenter changes/manipulates in the experiment Independent Variable: What the experimenter changes/manipulates in the experiment Dependent Variable: Data collected during the experiment Dependent Variable: Data collected during the experiment Constants: Materials found in both groups Constants: Materials found in both groups

Understanding Experimental Design Control and Experimental Groups. Why? Control and Experimental Groups. Why? Large Sample Size. Why? Large Sample Size. Why? Only 1 Independent Variable Should Be Tested. Why? Only 1 Independent Variable Should Be Tested. Why? All Constants Must Be the Same in Both Groups. Why? All Constants Must Be the Same in Both Groups. Why?

Correct the Practice Regents Question Plants respond to their environment in many different ways. Plants respond to their environment in many different ways. Design an experiment to test the effects of one environmental factor, chosen from the list below, on plant growth. Design an experiment to test the effects of one environmental factor, chosen from the list below, on plant growth. Acidity of precipitation Acidity of precipitation Temperature Temperature Amount of water Amount of water

Practice Regents Question Control Group Experimental Group How could the experimental group be different from the control group?

Practice Regents Question State Hypothesis State Hypothesis List the materials in the control group List the materials in the control group List the materials in the experimental group List the materials in the experimental group How is the experimental group different from the control group? How is the experimental group different from the control group? What is the Independent Variable in this experiment? What is the Independent Variable in this experiment? What is the Dependent Variable in this experiment? What is the Dependent Variable in this experiment? If _______, then _______. Sun Plant Water Soil (No water or Acid or High Temp) No water or Acid or High Temp Height/Growth of Plant Sun Plant Water Soil No water or Acid or High Temp

Math for APES Calculations Without Calculators

What are Significant Figures? If you take your calculator and multiply times 2.3 you will get as a result. These results are "correct" in a pure mathematical sense that assumes you know the values of the initial numbers exactly. If you take your calculator and multiply times 2.3 you will get as a result. These results are "correct" in a pure mathematical sense that assumes you know the values of the initial numbers exactly is actually is actually is actually is actually In the real world when we make measurements of anything, the value we get is not known exactly, but rather has some uncertainty associated with it. How large this uncertainty is depends to a high degree on the type of measuring device used as well as how it is used. In the real world when we make measurements of anything, the value we get is not known exactly, but rather has some uncertainty associated with it. How large this uncertainty is depends to a high degree on the type of measuring device used as well as how it is used.

What are Significant Figures? For example, suppose that three people were told to determine the length of a piece of wood and were given a tape measure whose smallest markings were at 0.1 centimeter intervals. For example, suppose that three people were told to determine the length of a piece of wood and were given a tape measure whose smallest markings were at 0.1 centimeter intervals.Person Value measured for length cm cm cm

Atlantic Pacific Method to Sig Figs Atlantic Decimal Absent Count Sig Figs  Pacific Decimal Present Count Sig Figs  **Start counting with the first non- zero (1-9) After that all digits count (0-9)

Determining Sig-Figs Multiplication and Division Use the smallest number of significant digits to round off the answer!

Determining Sig-Figs Addition and Subtraction Line up decimal points. You must round to the least precise number.

Scientific Notation Scientific Notation is a way to express, numbers in the form of exponents as the product of a number (between 1 and 10) and raised to a power of 10. For use 6.5 x 10 5 For use 5.43 x Always convert large and small numbers into Scientific Notation. Remember: APEnvi = Calculations without Calculators!

When using scientific notation remember to have one number to the left of the decimal and to always use the correct significant figures.

Determining Exponents Multiplication and Division Multiplication Add Exponents Division Subtract Exponents

When multiplying numbers with base 10 exponents, multiply the first factors, and then add the exponents. Example, (3.1 x 105) (4.5 x 10 5 ) = x or 1.4 x When dividing numbers, the exponents are subtracted, numerator exponent minus denominator exponent. Example: 9 x 10 5 = 3 x x 10 3

Dimensional Analysis The following formula based on the cancellation of units is useful: old unit x new unit = new unit 1 old unit Example: Convert 12 km into mm. Report your answer using scientific notation. 12 km x 1000m x 1000 mm = mm = 1.2 X 10 7 mm 1 km 1 m Example: Convert 72 ft into m. Hint: 3 feet in 1 yard and.914 meters in 1 yard 72.0 ft x 1 yard x.914m = 22 m 3 ft 1 yard ANSWER

Conversions from US to metric will probably be given and do not need to be memorized. They should be practiced, however. Gallons to Liters 1 gal= 3.8 L Liters to Gallons1 L, l=.264 gal Meters to Yards1 m= yd Yards to Meters1 yd=.914 m Grams to Ounces1 g=.035 oz Ounces to Grams 1 oz= g Kilograms to Pounds1 kg= 2.2 lb Pounds to Kilograms1 lb= 454 g Miles to Kilometers1 mi= 1.609km Kilometers to Miles1 km=.621 mi

GigaG10 9 = MegaM10 6 = Kilok10 3 = Hecto h10 2 = 100 Dekadk10 1 = 10 Base Unit(m, l, g)10 0 =1 Decid10 -1 =.1 Centic10 -2 =.01 Millim10 -3 =.001 Micro μ10 -6 = Nanon10 -9 =

Know How to Calculate Percentages! Total # = % Out of 100 Example: If 200 households in a town of have solar power, what percent does this represent? answer = 2.0% Example: If a city of population 10,000 experiences 100 births, 40 deaths, 10 immigrants, and 30 emigrants in the course of a year, what is its net annual percentage growth rate? answer = 0.40% ANSWER

Know Some Simple Energy Calculations 2004 Exam: West Freemont is a community consisting of 3000 homes. The capacity of the power plant is 12 megawatts (MW) and the average household consumes 8,000 kilowatt hours (kWh) of electrical energy each year. The price paid for this energy is $0.10 per kWh. (a) Assuming that the existing power plant can operate at full capacity for 8,000 hours per year, how many kWh of electricity can be produced by the plant in one year? 12 MW X 1000 kW X 8000 hours = kWh/year 12 MW X 1000 kW X 8000 hours = kWh/year 1 MW Year or 9.6 X 10 7 kWh/year 1 MW Year or 9.6 X 10 7 kWh/year (b) How many kWh of electricity does the community use in one year? 3000 houses X 8000 kWh = kWh/yr or 3000 houses X 8000 kWh = kWh/yr or yr 2.4 X 10 7 kWh/yr yr 2.4 X 10 7 kWh/yr ANSWER

Tips to Solving Problems Show ALL of your work and steps of calculations, even if they are so simple you think they are implied. No Work, No Credit! Show ALL of your work and steps of calculations, even if they are so simple you think they are implied. No Work, No Credit! Write out all your numerical information! Write out all your numerical information! Watch Out For Units!!!! Watch Out For Units!!!! Answers should make sense! LOOK them over before you finish. Answers should make sense! LOOK them over before you finish. Example: No one is going to spend 1 billion dollars per gallon of water or $10,000 per kWh electrical energy! Example: No one is going to spend 1 billion dollars per gallon of water or $10,000 per kWh electrical energy!

Data for the Lab

Soil Salinization: An Experimental Design You and your partners will act as a team of consultants hired by a group of farmers who are concerned about how increasing salt concentrations interfere with the germination of four different crop seeds. You and your partners will act as a team of consultants hired by a group of farmers who are concerned about how increasing salt concentrations interfere with the germination of four different crop seeds. You will design an experiment to test the effects of Salinization on plant growth on crops seeds of your choice. You will design an experiment to test the effects of Salinization on plant growth on crops seeds of your choice.

Soil Salinization: An Experimental Design Soil Salinization occurs when water sprayed onto crops evaporates leaving behind salt crystals formed from the electrolytes in the water. Over time this salt accumulates and becomes a challenge for farmers. Soil Salinization occurs when water sprayed onto crops evaporates leaving behind salt crystals formed from the electrolytes in the water. Over time this salt accumulates and becomes a challenge for farmers. On your graphs be sure to indicate the: On your graphs be sure to indicate the: LD50 (Lethal Dose-50%) – Dose that is reported to be lethal to 50% of the population. LD50 (Lethal Dose-50%) – Dose that is reported to be lethal to 50% of the population. Threshold Level of Toxicity- Maximum dose that has no measurable effect Threshold Level of Toxicity- Maximum dose that has no measurable effect Example: Most amount of salt that can be present without changing plant growth. Example: Most amount of salt that can be present without changing plant growth.

Soil Salinization: An Experimental Design- Calculating Salt Concentrations (w/v)% concentration = mass of solute (g) x 100% (w/v)% concentration = mass of solute (g) x 100% volume of solution (mL) volume of solution (mL) Based on your salt concentrations and selected volume of water calculate the mass of salt needed for each selected salt concentation. Based on your salt concentrations and selected volume of water calculate the mass of salt needed for each selected salt concentation. Then find the amount of salt needed to created the proper salt concentration. Then find the amount of salt needed to created the proper salt concentration. Example: Find the amount of salt to use when making a 0.5% salt solution in 10ml of H2O. Example: Find the amount of salt to use when making a 0.5% salt solution in 10ml of H2O. 0.5% = mass of solute(g) x 100% 0.5% = mass of solute(g) x 100% 10 mL 10 mL 0.05 g = mass of solute 0.05 g = mass of solute

Calculations We Will See in the Future

Rule of 70 Based on exponential growth Based on exponential growth Doubling Time = 70/annual growth rate Doubling Time = 70/annual growth rate For example, if a population is growing at an annual rate of 2%, the number of years it will take for that population to double can be found by dividing 70 by 2, i.e., DT = 70/2 = 35 years. Calculate the doubling time for a population growing at 1.4%. Answer = 70/1.4 = 50 years

Half Life Calculations Example: A sample of radioactive waste has a half- life of 10 years and an activity level of 2 curies. A sample of radioactive waste has a half- life of 10 years and an activity level of 2 curies. After how many years will the activity level of this sample be 0.25 curie?

“Per capita” Graph Interpretation

Interpolating and Extrapolating Data Interpolating and Extrapolating Data