Scientific Investigations

What are the three types Scientific Investigations? Descriptive Investigation Comparative Experiment Involves describing and/or quantifying parts of a natural or man-made system Involves collecting data on different organisms, objects or features , or collecting data under different conditions (e.g. times of the year, temperatures, locations) to make a comparison. Involves designing a fair test in which variables are actively manipulated, controlled and measured in an effort to gather evidence to support or not support a causal relationship

Basics steps of an experimental investigation 1.Observation 2.Hypothesis 3.Experiment 4.Data Collection 5.Conclusion 6. Revise/Retest Let’s discuss each step in detail

What is an Observation? Gathered through your senses A scientist notices something in their natural world

There are 2 types of observations in an experiment? Qualitative: use your senses to observe the results. OBSERVABLE Quantitative: use tools (rulers, balances, graduated cylinders) to produce numerical data. MEASURABLE

Is your observation qualitative or quantitative? Make your observation Is your observation qualitative or quantitative?

What is a Hypothesis? a specific, testable prediction about what you expect to happen in your investigation Sometimes written as If…Then… statements

Checking for Understanding Take out your white boards and markers Is it a Hypothesis?

Testable (T) or Untestable (U) Bacterial growth increases as temperature increases. Old people are frail. U T Plants prefer country music to rock music Objects of different masses dropped from the same height will accelerate toward the earth at the same rate U If you play music to plants for 8 hours a day they will have increased growth T T More than 70% of students report that they prefer chemistry to physics Individuals that take daily doses of Aspirin for more than 6 months have a 50% increase in reported instances of stomach damage T Physics is far more interesting than chemistry U T Human bone density tends to decrease as age increases People that take daily doses of aspirin feel better. T U

What is an Experiment? A set of actions to test a hypothesis Uses variables – factors in an experiment that change A valid (correct) controlled experiment will only test ONE variable at a time

What are the two important GROUPS in an Experiment? Control Group used for COMPARISON NOT being tested (what is normally done) Experimental Group the subjects being TESTED

Within the Experimental Group are variables Independent Variable (IV): Factor that is purposely MANIPULATED (CHANGED) in the experiment Dependent Variable (DV): Factor that RESPONDS as a result of the IV (it’s observed or measured)

CONSTANTS those conditions in an experiment that are kept the same for the experimental group.

Experiment investigation Scenario Ten seeds were planted in each of five pots containing 700g of “ Sure Potting Soil”. Each day for 40 days, spring water is given weekly as follows: Pot #1, 50 ml; Pot #2, 100 ml; Pot #3, 150 ml; Pot #4, 200 ml; Pot #5, 250 ml The recommended amount of water use is 150 ml. The student decided to measure the height of each plant at the end of the experiment. Identify the Following: A. Control Group: - Pot #3 B. Experimental Group: - seeds in Pot#1,2,4,5 1. Independent Variable: - Amount of water 2. Dependent Variable: - height of each plant 3. Constants: - duration, “sure potting soil” , 700g of soil, spring water

What is Data? information gathered during the experiment (quantitatively or qualitatively) it can be represented in the form of notes, charts, graphs, pictures etc.

What is the Conclusion? The answer to the hypothesis based on the data obtained from the experiment

Why Retest? In order to verify the results, the experiment must be retested The more trials performed the more accurate the results.

Can you state the steps involved in solving a problem? 1)Identify a Problem 2) State Observations about the problem 3) Form a Hypothesis about the problem (if…then…) 4) Design an Experiment to test the hypothesis 5) Collect Data 6) Form a Conclusion 7) Retest

What is a Scientific Theory? An explanation of an observation that has been confirmed through repeated testing It unites and explains a broad range of observations It remains valid as long as there is no evidence to dispute it It is not easily disproven – BUT CAN BE!

So then, What is the difference between a hypothesis and a theory? A hypothesis attempts to answer questions by putting forth a prediction or reasonable explanation that has not been thoroughly tested. A theory, on the other hand, has already undergone extensive testing by various scientists and is generally accepted as being an accurate explanation of an observation. (This doesn’t mean the theory is correct; only that current testing has not yet been able to disprove it, and the evidence as it is understood, appears to support it.)