Introduction to Science Unit 1: Chapter 1

1.1 The Nature of Science Natural Science Biological Physical Earth Science Science Science Botany Chemistry Meterology Ecology Physics Geology Zoology

Critical Thinking In science, we use critical thinking. What is critical thinking? How do we use it?

The Scientific Method Step 1: Ask questions. At this stage, the only thing a scientist does is ask questions. Why does my hair get frizzy on rainy days? Why does popcorn burn after 5 minutes, but not 4 and a half? How do certain medications affect blood pressure? The main objective here is to find a topic that interests you and that can be answered or solved with an experiment.

Step 2: Perform research. It’s very important that you do step 2 before step 3. Why? In order for you to form a hypothesis, you must have some background information. Research, interviews, and surveys can help with this process. The more information you start with, the better your experiment can be and the more able you’ll be to analyze your results.

Step 3: Form a hypothesis. As mentioned before, you must have background info to do this. A hypothesis is also called an educated guess. This means that it is a predicted answer or solution based on prior knowledge, which comes from what you gathered in step 2. We will use the “if/then” format for writing a hypothesis, which identifies the independent and dependent variables within an experiment. (if=IV, then=DV)

Step 4: Conduct an experiment. The fun part! Conducting experiments can mean many things. For example, sometimes a simple survey is an experiment. Observation, testing, and trial and error are all part of this step. This is also a good time to talk about lab safety, since most experiments will take place in a laboratory setting.

Lab Safety A few reminders when working in the lab: No food or drink in the lab unless I specifically tell you otherwise. Always read, re-read, re-re-read instructions, and be sure to ask questions before you get too far into an experiment. Please be mindful of the fact that there will often be close to 30 people in the lab with you and that your safety and theirs is ALWAYS your first concern. Familiarize yourself with lab equipment, safety symbols, and the location of first aid materials before beginning an experiment.

Step 5: Analyze data. This is the part where you draw graphs, make data tables, and do calculations. It’s very important that your recordings are accurate and that your findings are well organized and easy for others to understand. We will talk more about graphs in a little while. Also at this stage, it’s important that you describe what all your numbers mean. Make sure to label everything clearly and to interpret the meaning of your graph or table.

Step 6: Draw conclusions. Though the title simply says to make conclusions, there are really several components to this step. The number one objective in this step is to answer your original question. Was your hypothesis supported or will you reject it based on what your experiment showed? Secondary to this is suggesting improvements that can be made for more accurate results, identifying factors that might have affected your results negatively, and tossing around ideas for expanding on what you discovered.

Step 7: Repeat. In the scientific community, no one will believe anything you say unless you’ve conducted the experiment several times and come up with the same results each time. If your results should vary, it’s your job to figure out why and to be able to fix it so that you can duplicate the experiment with the expected results and that others can as well.

Variables - dependent and independent The independent variable in an experiment is the variable that you change and control. The dependent variable is the variable that is changed because of what you are doing. For example, the amount of growth in a plant depends on how much water it receives.

Controlled experiments are set up so that only one thing is changed at a time. What is the benefit of this? If you are manipulating several things at once, it’s impossible to determine what is actually causing a specific outcome.

1.2: The Way Science Works A major component of any scientific experiment is collecting data and taking measurements. When scientists take measurements, they use the metric system. It’s important to understand how the metric system works and its benefits.

The metric system is useful in science because: It is based on the multiples of the number 10. It uses the same prefixes regardless of what quantity is being measured. It is used throughout the world. It is easy to convert from one unit to another.

Units of Measurement Quantity Unit Abbreviation Length meter m Mass gram g Time second s Temperature Celcius C Current ampere A Amount mole Mol Volume Liter L

Prefixes for Large Measurements Symbol Meaning Multiple of Base Unit Kilo- K thousand 1000 Hecto- H hundred 100 Deka- D ten 10 *Note: changing units from deka- to kilo- means that you will divide by 100, not 20.

Prefixes for Small Measurements Symbol Meaning Multiple of Base Unit Deci- d 1/10 0.1 Centi- c 1/100 0.01 Milli- m 1/1000 0.001 *Note: changing units from milli- to deci- means that you will multiply by 100, not 20.

A Helpful Mnemonic Device King Hector Died Unexpectedly Drinking Chocolate milk Kilo Hecto Deka Unit (m, L, g, s) Deci Centi Milli

Dimensional Analysis: Conversions If you are converting a larger unit to a smaller unit, you will move the decimal to the right (or multiply) and end up with a larger number. If you are converting a smaller unit to a larger unit, you will move the decimal to the left (or divide) and end up with a smaller number.

Practice Problems Convert 550 mm to m. Convert 3.5 s to ms. Convert 1.6 kg to g.

Solutions 550 mm = 0.55m 3.5 s = 3500 ms 1.6 kg = 1600 g

1.3: Organizing Data Data is best presented using graphs. There are three types of graphs, each of which can be used for specific situations.

A bar graph is best used to compare similar data for several individual items or events.

Line graphs are used to show continuous change. Line graphs contain an independent variable (the factor that doesn’t change) and the dependent variable (the factor that changes).

Pie charts are used to show the parts of a whole, or the percentages of individual items or events that make up the entire item or event.

What do you think? Which graph might a company use to convince a buyer that he/she will see change (such as hair growth or whiter teeth) if they buy the product? Which graph would show how much oxygen is present in the atmosphere? Which graph would be used to show the height differences in males versus females for several different age groups?

Must-Haves 5 things every graph must have: A title - this needs to be very specific and should include both the independent and dependent variables. A key - this can be a legend to the side of the graph, or you can label the lines or bars within the graph. X- and y-axis labels - the x-axis shows the independent variable and the y-axis shows the dependent variable. Units of measurement - for example, tell if height is measured in mm or km, if time is measured in seconds or years, etc. An accurate graph - this means the graph needs to be the proper type and it must make sense.

Significant Figures Any time you’re dealing with measurements, you must have accuracy and precision. Counting significant figures in your measurements is one way to make sure that your answer is as precise (exact) and accurate (close to the actual value measured) as possible.

The Rules 1. ALL non-zero numbers (1,2,3,4,5,6,7,8,9) are ALWAYS significant. 2. ALL zeroes between non-zero numbers are ALWAYS significant. 3. ALL zeroes which are SIMULTANEOUSLY to the right of the decimal point AND at the end of the number are ALWAYS significant. 4. ALL zeroes which are to the left of a written decimal point and are in a number >= 10 are ALWAYS significant.

Examples How many significant figures are in the following numbers? 48,923 3,000,000 3.967 10.0 900.06 501.040 0.0004 8.1000

Answers 48,923 = 5 sig figs (rule 1) 3.967 = 4 sig figs (rule 1) 0.0004 = 1 sig fig (rules 1, 4) 3,000,000 = 1 sig fig (rule 1) 10.0 = 3 sig figs (rules 1, 3, 4) 501.040 = 6 sig figs (rules 1, 2, 3, 4) 8.1000 = 5 sig figs (rules 1, 3)

Scientific Notation A helpful way to check rules 3 and 4 for significant figures is to write the number in scientific notation. If you can/must get rid of the zeroes, then they are NOT significant. Scientific notation is a shorthand method of writing really large or really small numbers by multiplying those numbers by a factor of 10.

Writing in Scientific Notation Power of 10 Decimal Equivalent 10^4 10,000 10^3 1,000 10^2 100 10^1 10 10^0 1 10^-1 0.1 10^-2 0.01 10^-3 0.001

The Rules In scientific notation, the significant figures are always shown. The trick to shortening the number is to move the decimal to the space after the first sig fig. However many places you moved the decimal is the exponent that you multiply 10 by. If you moved the decimal to the right, the exponent is negative. If you moved the decimal to the left, the exponent is positive.

Examples How do you write the following numbers using scientific notation? 800,000,000 0.0015 60,200 0.00095 8,002,000 0.00000000006

Answers 800,000,000 = 8.0 x 10^8 0.0015 = 1.5 x 10^-3 60,200 = 6.02 x 10^4 0.00095 = 9.5 x 10^-4 8,002,000 = 8.002 x 10^6 0.00000000006 = 6.0 x 10^-11