Integrated Physics and Chemistry Introduction to Science
VOCABULARY 1. quantitative data 13. kilo- 2. qualitative data 14. centi- • scientific method 15. milli- • variable 16. density • hypothesis • control group • experimental group • independent variable • dependent variable • theory • SI • meter
How is Science Done? Science begins with an observation. Observation is the process of gathering information about events or processes in a careful, orderly way. Data is the information gathered from making observations.
There are two types of data: Quantitative data are numbers, and are obtained by counting or measuring. Qualitative data are descriptions, and involve characteristics that cannot be counted.
Scientific Methods The scientific method is a series of steps used by scientists to solve a problem or answer a question. The Steps to the Scientific Method: Observation / Asking a Question Form a Hypothesis Design a Controlled Experiment Record and Analyze Results Draw Conclusions
Step 1: Observation / Asking a Question Step 2: Form a Hypothesis Hypothesis: A problem or a question must first be identified. a possible explanation to the question or problem. It is simply a prediction and has not yet been proven or disproven. It must be stated in a way that it is testable. A statement is considered “testable” if evidence can be collected that either does or does not support it. How much water can a root absorb? Why does a plant stem bend toward the light? What effect does temperature have on heart rate?
Step 3: Designing a Controlled Experiment 1. The factors in an experiment that can be changed are called variables.Some example of variables would be: changing the temperature, the amount of light present, time, concentration of solutions used. 2. A controlled experiment works with one variable at a time.If several variables were changed at the same time, the scientist would not know which variable was responsible for the observed results.
Step 3: Designing a Controlled Experiment • 3. In acontrolled experiment, only one variable is changed at a time. All other variables should be unchanged or “controlled.” • 4. An experiment is based on the comparison between a control group with an experimental group. • These two groups are identical except for one factor. • The control group serves as the comparison. It is the same as the experiment group, except that the one variable that is being tested is removed. • The experimental group shows the effect of the variable that is being tested.
Example:In order to test the effectiveness of a new vaccine, 50 volunteers are selected and divided into two groups. One group will be the control group and the other will be the experimental group. Both groups were given a pill to take that was identical in size, shape, color and texture. Even though the volunteers are given identical looking pills, the control group will not actually receive the vaccine. Describe the control group. Describe the experimental group. What variables are kept constant? What variable is being changed? This group will receive the vaccine. The size, shape, color, and texture of the pill. Does the pill contains the vaccine or not?
There are two variables in an experiment: In the previous example, what is the independent variable? 1. The independent variable is the variable that is deliberately changed by the scientist. It is the addition of the vaccine to the pills that were given to the volunteers. In the previous example, what is the dependent variable? 2. The dependent variable is the variable that is measured in an experiment. The dependent variable is the data we collect during the experiment. This data is collected as a result of changing the independent variable. The observed health of the people receiving the pills.
REVIEW • A control group is a group in an experiment that receives no experimental treatment. • The independent variable in an experiment is the factor, or variable, that is being changed. • The dependent variable in an experiment is the factor, or variable, that is being measured.
Step 4: Recording and Analyzing Results Record the Results: The data that has been collected must be organized and analyzed to determine whether the data is reliable. Analyze the Results: Does the data support or not support the hypothesis?
Step 5: Drawing Conclusions The evidence from the experiment is used to determine if the hypothesis is provenor disproven. Experiments must be repeated over and over. When repeated, the results should always be the same before a valid conclusion can be reached.
Forming a Theory A theory is a broad and comprehensive statement of what is thought to be true. A theorymay be formed after the hypothesis has been tested many times and is supported by much evidence. A theory is supported by considerable evidence.
Standards of Measurement – Section 2 • A standard is an exact quantity that is used for comparison. • In 1960, the International System of Units was devised. The SI is universally accepted and understood by scientists throughout the world. • Each type of SI measurement has a base unit. • The SI system is easy to use because it is based on multiples of ten. Prefixes are used with the names of the units to indicate what multiple of ten should be used with the units.
International System of Units • The meter is the base unit of length. • The kilogram is the base unit for mass. • The second is the base unit for time. • The kelvin is the base unit for temperature. • The mole is the base unit for the amount of a substance. • The ampere is the base unit for electric current. • The prefix kilo- means “1,000.” • One kilometer equals 1,000 meters. • One kilogram equals 1,000 grams. • The prefix deci- means “one-tenth.” • One decimeter equals one-tenth of a meter.
Converting Between SI Units • Conversion factors are used to change from one unit to another. • A conversion factor is a ratio that is equal to one. For example, there are 1000 mL in 1 L, so 1000 mL = 1 L. • This can be written as: 1,000 mL 1 L • To convert units, multiply by the appropriate conversion factor.
Converting Between SI Units • For example, to convert 1.255 L to mL, multiply 1.255 L by a conversion factor. • Use the conversion factor with new units (mL) in the numerator and the old units (L) in the denominator. • 1.255 L X 1,000 mL = 1,255 mL 1 L
km Metric Units mm cm m The basic unit of length in the metric system in the meter and is represented by a lowercase m. Click the image to watch a short video about the meter. Metric Units 1 Kilometer (km) = 1000 meters 1 Meter = 100 Centimeters (cm) 1 Meter = 1000 Millimeters (mm)
1 centimeter = 10 millimeters What is the length of the line in centimeters? _______cm What is the length of the line in millimeters? _______mm What is the length of the line to the nearest centimeter? ________cm HINT: Round to the nearest centimeter – no decimals. Measuring Length How many millimeters are in 1 centimeter?
Measuring Volume • Volume is the amount of space occupied by an object. • To calculate volume, multiply the length times the width times the height. V =L x W x H • The volume of an object is always expressed in cubic measurement. (m3) • To measure liquid volume, measure the capacity of the container that holds that amount of liquid. • The most common units for expressing liquid volume are liters and milliliters.
Measuring Matter • Massis a measurement of the quantity of matter in an object. • Mass is usually expressed in kilograms or grams. • Density is the mass per unit volume of a material. • Density can be found by dividing an object’s mass by the object’s volume. D = M V
Kilogram Prototype kg Metric Units cg mg g Mass refers to the amount of matter in an object. The base unit of mass in the metric system in the kilogram and is represented by kg. Click the image to watch a short video about mass. Metric Units 1 Kilogram (km) = 1000 Grams (g) 1 Gram (g) = 1000 Milligrams (mg)
Once you have balanced the scale, you add up the amounts on each beam to find the total mass. Measuring Mass We will be using triple-beam balances to find the mass of various objects. The objects are placed on the scale and then you move the weights on the beams until you get the lines on the right-side of the scale to match up.
1st– Place the item on the scale. 2nd – Slide the large weight to the right until the arm drops below the line. Move the rider back one groove. Make sure it “locks” into place. 3rd– Repeat this process with the top weight. When the arm moves below the line, back it up one groove. 4th – Slide the small weight on the front beam until the lines match up. Measuring Mass – Triple-Beam Balance 5th – Add the amounts on each beam to find the total mass to the nearest tenth of a gram.
kL Metric Units mL L cL Volume is the amount of space an object takes up. The base unit of volume in the metric system in the liter and is represented by L or l. Metric Units 1 liter (L) = 1000 milliliters (mL) 1 milliliter (mL) = 1 cm3 (or cc) = 1 gram Click the image to watch a short video about volume.
What causes the meniscus? A concave meniscus occurs when the molecules of the liquid attract those of the container. The glass attracts the water on the sides. Measuring Volume We will be using graduated cylinders to find the volume of liquids and other objects. Read the measurement based on the bottom of the meniscus or curve. When using a real cylinder, make sure you are eye-level with the level of the water. What is the volume of water in the cylinder? _____mL
Measuring Liquid Volume What is the volume of water in each cylinder? Images created at http://www.standards.dfes.gov.uk/primaryframework/downloads/SWF/measuring_cylinder.swf A B C Pay attention to the scales for each cylinder.
9 cm 8 cm 10 cm We can measure the volume of an irregular object by usingwater displacement. Amount of H2O with object = ______About of H2O without object = ______Difference = Volume = ______ Measuring Solid Volume We can measure the volume of regular object using the formula length x width x height. _____ X _____ X _____ = _____
Measuring Matter • The measurement unit for density is g/cm3 and is a combination of SI units. • A derived unit is a unit obtained by combining different SI units. • An SI unit multiplied by itself is also a derived unit. • A cubic meter, expressed with an exponent (m3) is an example of a derived unit.
Measuring Time and Temperature • Time is an interval between two events. The SI unit for time is the second. • Temperature is the measuring a how hot or cold something is and is usually measured on the Celsius (C) scale. • On this scale, the freezing point of water is 00C, and the boiling point of water is 1000C. • Between these points, the scale is divided into 100 equal divisions.
Kelvin and Fahrenheit • The SI unit of temperature is the kelvin (K). • Zero on the Kelvin scale (0 K) is the coldest possible temperature, and is also known as absolute zero. That is equal to -2730C, which is 2730 below the freezing point of water. • To convert Celsius to Kelvin, add 273 to the Celsius reading. So, on the Kelvin scale, water freezes at 273 K and boils at 373 K.
Celsius and Fahrenheit • On the Fahrenheit scale, water freezes at 320F and boils at 2120F. • To convert from Celsius to Fahrenheit, use this equation: C = 5(F – 32)/9 • To convert Fahrenheit to Celsius use this formula: F = (1.8 x C) + 32
Temperature Scales absolute zero water freezes water boils • Fahrenheit -4600 320 2120 • Celsius -2730 00 1000 • Kelvin 0 273 373
Communicating With Graphs – Section 3 • A graph is a visual display of information or data. • A line graph can show any relationship where the dependent variable changes due to a change in the independent variable. • A bar graph is useful for comparing information collected by counting. • A circle graph, or pie graph, is used to show how some fixed quantity is broken down into parts. • The circular pie represents the total, and the slices represent the percentages of the total.
Making a Data Table As scientists collect data, it must be recorded in an organized fashion. Any time data is collected in an experiment, it is most often presented in a table. The data table must have a title, rows, columns, and headings. The title should be placed at the top and tells the observer what information is contained in the table. At the top of each column should be a heading that tells you what information is in the column.
Example 1: Make a data table for the following information The following data was collected for the growth of a plant. On day 0, there was 0 growth. On day 1, there was 2.0 cm of growth. On day 2, there was 5.3 cm of growth. On day 3, there was 6.1 cm of growth. On day 4, there was 8.4 cm of growth. On day 5, there was 11 cm of growth. The Growth of a Plant in Centimeters Day Growth 0 1 2 3 4 5 0 cm 2.0 cm 5.3 cm 6.1 cm 8.4 cm 11 cm In the top row, place the title of your data table. In the next row, place the two column heads. In the remaining rows, fill in the data.
Example 2: Make a data table for the following information The number of cricket chirps was recorded on two different nights at various temperatures (Celsius). On night 1, the following data was obtained: Temp 16, cricket chirps 33; Temp 18, cricket chirps 38; Temp 20, cricket chirps 42; Temp 22, cricket chirps 46; Temp 24, cricket chirps 50. On night 2, the following data was obtained: Temp 16, cricket chirps 32; Temp 18, cricket chirps 36; Temp 20, cricket chirps 41; Temp 22, cricket chirps 43; Temp 24, cricket chirps 51. The Number of Cricket Chirps Recorded at Different Temperatures In the top row, place the title of your data table. Night 1 Night 2 In the next row, place the two column heads. Since data were collected on two different nights, you will need 4 columns. Temp # Chirps Temp # Chirps 16 18 20 22 24 16 18 20 22 24 33 38 42 46 50 32 36 41 43 51 In the remaining rows, fill in the data.
Making a Line Graph Line graphs show data plotted as points that are connected by a line. Line graphs are often used to show change over time and can be used to compare two or more sets of data. Before a line graph can be constructed, you must identify the two variables that will serve as x andycoordinates on the graph. These are called the independent variable and the dependent variable.
Making a Line Graph The independent variable is the one being manipulated or changed during the experiment. The independent variable is always placed on the x-axis or horizontal axis. An easy way to remember this is to ask yourself the questions: “What did I know before I did the experiment?” (independent variable) “What did I learn by doing the experiment?” (dependent variable) The dependent variable is the observed result of the independent variable being changed. The dependent variable is always placed on they-axis or vertical axis.
Using the grid below, make a line graph using the information in Example 1. First determine which variable to place on the horizontal (x) axis and which variable to place on the vertical (y) axis. The Growth of Plants in Centimeters 2 4 6 8 10 12 Label each axis appropriately. Growth (cm) Scale each axis appropriately. Title your graph. 0 1 2 3 4 5 6 Plot the points on the graph. Time (days)
Using the grid below, make a line graph using the information in Example 2. First determine which variable to place on the horizontal (x) axis and which variable to place on the vertical (y) axis. Number of Cricket Chirps Recorded at Various Temperatures 0C Label each axis appropriately. 10 20 30 40 50 # cricket chirps Scale each axis appropriately. Title your graph. Plot the points on the graph. 16 18 20 22 24 Since this graph will have two different lines, be sure to label each line. Temp (0C)
Your graph should look like this: Since this graph will have two different lines, be sure to label each line.