Chapter 1: The Nature of Science

1.1 : The Methods of Science1.2 : Standards of Measurement

1.3 : Communicating with Graphs

1.1 The Methods of Science

Science

• A method for the study of the natural world

• A process that uses observation and investigation to gain knowledge about events in nature

Categories of Science

• Life Science – involves the study of living things

• Earth Science – involves the study of Earth and Space

• Physical Science – involves the study of matter and energy

Scientific Investigation

• Investigations can be done many different ways:

• Observations – simply looking at/watching an object(s) and recording what is taking place

• Experiments – testing the effect of one thing on another

Scientific Method

Scientific Method

• An organized set of 6 steps that scientists use to guide their investigations

1. State the problem – Why/How?

2. Gather Information – Learn as much as possible about the problem

• Some sources of scientific information are not accurate

3. Form a hypothesis – a possible explanation for a problem using what you know/observe

4. Test the hypothesis – Observations/Experiments

Scientific Method

• When testing the hypothesis:• Independent variable – the variable “you” change to see

how it will effect the dep. variable• Dependent variable – value changes according to changes

in other variables.[Cause and Effect Relationship]

• Constant – A factor that does not change• Control – the standard by which the experimental results

can be compared

All other variables should be help constant so that 1 variable is tested at a time

Scientific Method• Analyze Data – all data gained in the investigation should

be recorded, not just the data you like or think is right• This data can be organized into tables and graphs so that it

is easier to read

• Draw conclusions – Ask yourself if the data that you gained from the study supports or does not support your hypothesis• If your hypothesis is supported, you must repeat your study

to further prove that it is supported• If your hypothesis is NOT supported, you may want to go

back and reconsider the hypothesis

One should conduct repeated trials to limit random error in measurements

Scientific Bias

• Bias occurs when what the scientist expects changes how the results are viewed

• Findings are supportable when others can do the same experiment and get the same results

Models

• Models represent an idea, event, or object to better help people understand it

• Why create models?• Models are created in cases where objects are• Too large (ex. The solar system)• Too small (ex. Animal cells, the atom)• Too dangerous (ex. Computer models of nuclear

explosions)

Scientific Theory vs. Scientific Law

A theory can be used to explain a law!

Activity

1. Get into groups of four

2. On a sheet of paper to be turned in, put:• The problem• Information gathered (if applicable)• Form a hypothesis• How you would test your hypothesis (Include

dependent/independent variables, constant, control)• How you would analyze the data• Draw a conclusion and decide whether you support your

hypothesis or not

EXAMPLE

1. Problem – (Stated as a question) Does the temperature of a room affect the # of dreams you have?

2. Hypothesis • An educated guess • A possible answer to the problem• My hypothesis: If the room is hot, a subject will have

more dreams

EXAMPLE

3. Designing an Experiment• Control – 74° F• Constants – type of clothing, type of mattress, lighting,

same type of meal before bed, etc.• Independent variable - 45° F, 85° F, 95° F• Dependent variable – Number of dreams recorded the

next morning, or recording of brain activity

EXAMPLE

4. Analyzing the Data

Data Table – temperature vs. number of dreams

ex.

I could then place the information on a graph

Temperature Number of Dreams

74° F 2

45° F 4

85° F 7

95° F 7

EXAMPLE

5. Draw a conclusion

My data supports my hypothesis because the number of dreams increased as the

temperature of the room increased

Next, I would repeat the experiment several times to see if I get the same results

1.2 Standards of Measurement

Units and Standards

• Standard – an exact quantity that people agree to use to compare measurements• Ex. Using Feet/Hands to measure distance

across the room

• A measurement MUST include a number and a unit• English• Metric• SI

International System of Units (SI)

• Le Systeme Internationale d’Unites

• SI standards are accepted and understood by scientists around the world

• Each type of measurement has a base unit• Ex. Meter is the base unit for length, Liter for volume, Gram

for mass, second for time, kelvin for temp.

• Based on multiples of 10, prefixes are used with the names for the units to indicate the multiple of 10• ex. kilo – 1,000, so 1 kilometer = 1,000 meters

SI Base Units and Common SI Prefixes

SI Base Units

Quantity Measured

Unit Symbol

Length meter m

Mass kilogram kg

Time second s

Electric current ampere A

Temperature kelvin K

Amount of substance

mole mol

Intensity of light candela cd

Common SI Prefixes

Prefix Symbol Multiplying Factor

Kilo- k 1,000

Deci- d 0.1

Centi- c 0.01

Milli- m 0.001

Micro- μ 0.000 001

Nano- n 0.000 000 001

Dimensional Analysis

• Sometimes quantities are measured using different units

• To convert from one quantity to another conversion factors are used

1,000 mL/1 L = 1

• Ex: Convert 1.225 L to mL• Ex: Convert 3,075 mm to cm• Ex: Convert11 cm to mm• Ex: Convert 1 kg to g

Measuring Distance

Length – the distance between two points

• Choosing a Unit of length – the size of unit depends on what you are measuring• What measurement would you use to measure the

length of a pencil?• How about the distance to your house?

By using the correct unit, you avoid large numbers and numbers with many decimal places

Measuring Volume

• Volume (solid object) – the amount of space occupied by an object

V = l x w x h = units3

• Volume (liquid) – the capacity of the container that holds the amount of liquid1 mL = 1 cm3 (Easy to measure if you remember this when you use a graduated cylinder)

Ex. Convert 1.5 L to cm3

Measuring Matter

• Mass – a measurement of the quantity of matter in an object (golf ball vs. ping pong ball)

• Density – the mass per unit of volume of a material

Objects may have the same volume such as cylinders of aluminum, wood, or plastic

Even though they occupy the same space, the matter within them is packed differently

Density = Mass/Volume

• Derived Unit – a unit obtained by combining different SI units (g/cm3) / an SI unit multiplied by itself (m3)

Measuring Time & Temperature

• Temperature is a measure of how hot or how cold something isCelsius – common for measuring temperature

Fahrenheit

Kelvin – the SI unit of temperature

- 0 K is the coldest possible temp (absolute zero)

- Doesn’t use degrees

- Celsius = (F – 32)/1.8

- Kelvin = Celsius + 273

1.3 Communicating with Graphs

Graphs

• A graph is a visual display of information or data• Graphs make it easier to see patterns or trends in

experimental data

Line Graphs

Bar Graphs

Circle Graphs

Line Graphs

• Show any relationship where the dependent variable (y-axis) changes due to a change in the independent variable (x-axis)

• Best for showing continuous data

• Can you show more than one event on the same graph?• Yes! As long as the relationship between the variables

is the same

Line Graphs

Time*

Classroom Temperature

(C°)

A B C

0 16 16 16

5 17 17 16.5

10 19 19 17

15 20 21 17.5

20 20 23 18

25 20 25 18.5*minutes after turning on heat

0 5 10 15 20 2515

17

19

21

23

25

Classroom Temper-ature

ABCD

Time (min)

Tem

pera

ture

(C

els

ius)

Constructing Line Graphs

• Choose a scale with intervals on each axis in equal measurements

• Use the x-axis for the independent variable, just long enough to fit data

• Use the y-axis for the dependent variable with 2 data points more than is needed

• Use the same unit of measurement

• May need to show a break in the axis if your data is very large

Implications of Graphs

• Direct proportion – one variable increases as the other increases OR one variable decreases as the other decreases• Usually a straight line with

a positive slope• Shows a direct

relationship that changes at a constant rate

• What would a greater slope mean?

Implications of Graphs• Inverse proportion – the

product of two quantities is a constant• EX. V = f λ• Frequency and wavelength

are inversely proportional• As one quantity increases,

the other decreases

Bar Graphs

• Bar graphs are useful for comparing information collected by counting

• Each bar represents a quantity counted at a particular time

• Where should you plot independent and dependent variables?

• Points are not connected because the data is not showing how a change in one variable affects the other

Bar Graphs

20 21 22 23 24 250

1

2

3

4

5

6

Classroom Size

Number of Students

Nu

mb

er

of

class

room

s

Circle Graphs

• A circle (pie graph) is used to show how some fixed quantity is broken down into parts• Circle represents the

total• Slices represent the

parts, usually a percentage of the total

Gas50%

Steam25%

Electric10%

Coal10%

Other5%

Heating Fuel Usage

Making a Circle Graph

• Start with the total of what you are analyzing

• For each type, divide that amount by the total

• Multiply that decimal by 360° to determine the angle

• Ex. Total buildings = 7218 of the buildings use steam

18 ÷ 72 × 360° = 90°

Then, you would measure 90° on the circle to show 25%

Technology

• Technology is NOT the same as science

• Technology is the application of scientific discoveries to meet human needs and goals through the development of products and processes

• Engineering focuses on these processes by applying science to make products and design processes

Technological Design

• 4 Stages of Technological Design1. Problem identification

2. Solution design of a process or product

3. Implementation

4. Evaluation

• Requirements• Cost and time effectiveness• Materials that meet criteria (price, avaiblity, durability, not

harmful, etc.)

Benefits must exceed the risks

Scientific Investigation vs. Technological Design

Scientific Investigation Technological Design

Identifies a problem – asks a ? Identifies a problem or need

Researches related information Researches related information

Designs an investigation/experiment Designs a process or product

Conducts the investigation or experiment – repeated trials

Implements the design or the process – repeated testing

Analyzes the results Analyzes the results

Evaluates the conclusion – did the results refute or verify the hypothesis

Evaluates the process or product – did it meet the criteria

Communicates the findings Communicates the product or process

Science Labs and Safety Procedures

Labs

• In science labs, one uses various instruments to conduct investigations

• You must be able to identify and know how to use certain instruments

• You must always PUT SAFETY FIRST!!!

Graduated Cylinder – used to measure the volume of a liquid• Meniscus – the curve at the tip of a liquid in a graduated cylinder

• Measurements are read from the BOTTOM center of the meniscus

Thermometer – a device that measures temperature

Bunsen Burner

Funnel

Beaker

Pipette

Erlenmeyer flask

Measurements

• The last digit recorded is always estimated

• The more decimals in the recorded measurement, the greater the precision of the instrument• EX. A 100 mL graduated cylinder marked in 1 mL

increments measures exactly to the ones place

A 10 mL graduated cylinder marked in 0.1 mL increments can be read exactly to the tenths place

Which graduated cylinder is more precise?

Precision and Accuracy

• Precision – a measure of the degree to which measurements made in the same way agree with one another

• Accuracy – the degree to which the experimental value agrees with the true or accepted value

• It is possible to have high precision with low accuracy if the same error is involved in repeated trails of the experiment

Precision and Accuracy

Lab Safety

• Personal Safety –• Follow only designated lab procedures• Understand safety symbols• Wear proper clothing/shoes• Wear proper protective equipment (goggles, aprons)• Tie back loose hair• No eating/drinking• Use proper techniques for smelling, etc.

Lab Safety

• Work area safety –• Keep work area clear, uncluttered• Turn off burners/hot plates when leaving lab• Know locations and proper use of the fire extinguisher,

safety blanket, eyewash station, emergency shower, first aid kit

• Disconnect electrical devices• Clean up• Report incidents, spills, etc. to teacher IMMEDIATELY!