Scientific Method, Measurement, and Graphing

Scientific Method An organized way of

using evidence to learn about the natural world

A. Problem 1. observation- gathering

evidence using the senses (sight and hearing) Inference- a logical

interpretation based on prior knowledge or experience

A. Problem Observation- gathering evidence using

the senses (sight and hearing) Inference- a logical interpretation based

on prior knowledge or experience B. Hypothesis

A proposed scientific explanation to a problem

“if…then” statement

C. Experiment 1. Two parts to every experiment

A. control group- doesn’t receive a variable B. experimental group- receives a variables

2. Variable: the factors in an experiment that change (2 types) A. manipulated variable (independent variable)- the

variable that you can actually change Only one variable can be changed at a time On a graph, the IV is on the x axis

B. Responding variable (dependent variable)- the variable that will change or respond to the IV

3. Constant (controlled variable)- things that remain the same in an experiment

D. Record and Analyze Data Info collected during an experiment 2 main types of data:

1. Quantitative data- expressed as numbers obtained by counting or measuring

2. Qualitative data- descriptive and involves characteristics that can’t be counted

E. Conclusion Summary of experiment, using the data

to determine whether a hypothesis is supported or not

A conclusion must have 3 things Restate problem Briefly summarize results Does results support hypothesis?

Example: Do bacteria grow better at higher temps? Hypothesis: If the temp is higher, then the

bacteria will grow better Independent variable: temp Dependent variable: bacteria growth Constant: same type of bacteria, same type

and amount of agar Control: bacteria at room temp

Theory: a well tested explanation that unifies a broad range of observations. Theories can change.

Law: ideas that have been tested many times and accepted as true. Does NOT change.

II. Measurement Metric system (based on units of 10)

litterKm hecto deca meter dm m cm mm

gram

(Unusually)King Henry Died Drinking Chocolate Milk

Metric conversion examples 1. 100 L = ? mL 2. 2.5 m = ? km 3. 8 mg = ? g 4. 5.5 cm = ? mm 5. 4 kg = ? g

Metric conversion examples 1. 100 L = 100,000 ml 2. 2.5 m = 0.0025 km 3. 8 mg = 0.008 g 4. 5.5 cm = 55 mm 5. 4 kg = 4000 g

Measurement A. Length

1. Instrument = rulers, meter stick 2. Units = km, m, cm, mm

B. Mass- amount of matter in an object, doesn’t change Weight- measure of the pull of gravity,

changes 1. Instrument = triple beam balance 2. Units = kg, g, mg

C. Volume The amount of space an object takes up 1. Volume of a liquid:

A. instrument = graduated cylinder, beaker B. units= l , ml

Meniscus- curve in graduated cylinder 2. Volume of a regular-shaped solid:

Formula: length x width x height Unit = cubic centimeter (cm³)

3. Volume of an irregular-shaped object – water displacement

E. Temp 1. Instrument: thermometer 2. Units: degree Celsius 3. freezing point of water = 0ºC 32ºF Boiling point of water = 100ºC

212ºF Body Temp = 37ºC 98.6ºF

F. Density Mass per unit volume 1. Formula- mass/volume

Unit: g/ml 2. Ex: If the volume of a rock is 2 ml and the

mass is 4 g, what is the density? 4 g/ 2ml = 2 g/ml

III. GraphingA. Circle/Pie Graph- shows parts of a

whole (100%) Ex: Gases in the atmosphere

Nitrogen= 78%Oxygen = 21%Trace gases = 1%

B. Bar Graph Compares data - usually 1 quantitative,

1 qualitative data sets Example: Number of students taking a

foreign language 58 – Spanish 10 - German92 – French 9 – Italian

C. Line Graph Used to show change over time - 2

quantitative data sets

Temp (C) Number of bacterial colonies 10 1220 2530 5540 10050 82

Things to have on a graph: 1. Title 2. X and Y axis labeled

A. IV on X axis B. DV on Y axis

3. numbers on axis evenly distributed 4. Key if necessary