Unit 2 – Measurement & Data Notes
Unit Big Idea: Scientists use tools to collect, organize, and analyze data while conducting investigations.
Lesson 1 – Representing Data
Essential Question: How do scientists learn from data?
By the end of this lesson, you should be able to use tables and graphs to organize and analyze scientific
data.
- Data – facts, figures, and other evidence scientists gather when they conduct an investigation.
- data tables used to organize and record data collected
- Independent variable – variable that is manipulated in the investigation
- the “cause” in a cause and effect relationship – this is what you change
- found in the rows in a correctly set-up data table
- Dependent variable – variable that changes as a result of the manipulation of the independent variable
- the “effect” in a cause and effect relationship – this is the result/outcome. This is what you’re
doing the experiment to find out.
- found in the columns going across a correctly set-up data table
Different Types of Graphs/Charts
- Scatter plot – type of graph with points plotted to show a possible relationship between two sets of data
- horizontal x-axis (independent variable) and vertical y-axis (dependent variable)
- “line of best fit” – used to show the general relationship between the two variables – straight line
that is drawn to “fit” or come close to the most amount of data points
- bar graph – used to display and compare data that are in separate, or distinct, categories
- circle graph – used to show how each group of data relates to all of the data
- A trend shows the relationship between the variables studied in the experiment.
- Graphing data allows you to identify patterns, or trends, of the data.
- Graphing makes trends obvious to see – increasing, decreasing, staying the same
- line graph – shows continuous data, or data that can take on any value
- linear relationship – a line used in a line graph to show the relationship between the independent and
dependent variables
- line plot – shows frequency distribution of data, or how often data falls into certain intervals or
categories and a horizontal number line
- histogram – type of bar graph that also shows the frequency of data within equal intervals.
- use bars rather than Xs to represent data with each bar representing an interval
- no spaces between the bars
- Central tendency – describes a data set using only one number – the number is usually the middle
number. (ex. mean, median, & mode)
- range – how spread out the data are from the first point or value to the last – difference between the
largest & smallest numbers in a data set
- mean (average) – sum of all the values divided by the number of items in the data set.
- median – middle number in an ordered data set with an odd number of data points.
- begin by placing the data points in numerical order then find which is in the middle
- another way to describe the middle number with half the data above the median and half below.
- mode – number or numbers that occur most often in a data set
Lesson 2 Scientific Tools & Measurement
Essential Question: What are the tools and units used in science?
By the end of this lesson, you should be able to describe the different tools and units of measurement used
in scientific investigations.
- measurement – description that includes a number and a unit
- using standard units of measurement makes it possible for people in different places to work with
the same quantity and to repeat each other’s experiments
- International Systems of Units (SI) aka Metric System
- language for all scientific measurement
- seven base SI units for length, mass, time, temperature, amount of substance, electric current,
and light intensity
- each SI unit is represented by a symbol and measured with a specific tool or set of tools
- changing from one unit to another is easier because SI units are based on the number 10 – to
convert from one unit to another multiply or divide by a multiple of 10 (in other words move the
decimal either right or left by the number of zeros in the number you are multiplying or dividing
by)
Measurement
Length
Mass
Based Unit or Derived Unit Symbol
Meter
m
kilogram
kg
Time
Temperature
Volume
Second
Kelvin (Celsius)
Cubic decimeter (Liter)
Weight
Density
Newton
N
Grams per cubic centimeter g/cm3 or
(milliliter)
g/mL
s
K (C)
dm3 or L
Tools to Measure it
Meter stick, metric ruler, measuring tape
Balance (beam balance, electric balance)
and brass weight or weighted balance
Stopwatch
Thermometer
Graduated cylinder, beaker, volumetric
flask
Spring scale
Must be calculated using the equation:
Density = mass / volume
Prefix
kilohectodecadecicentimillimicro-
SI Prefixes
Symbol
Factor
k
1,000
h
100
da
10
1
d
0.1
c
0.01
m
0.001
μ
0.000001
- scientific notation – is a short way of
representing very large numbers or very small
numbers
- written in the form a x 10b
- ex. speed of light in standard notation is 300,000,000 m/s
Speed of light in scientific notation is 3 x 108 m/s
- the value of a is usually a number between 1 and 10
- the exponent b tells how many places the decimal is moved
- when decimal moves to the left, b is a positive number
- if the exponent is negative, move the decimal point b places to the left
- accuracy – is a description of how close a measurement is to the true value – it’s actual amount
- precision is the exactness of a measurement.
- the use of science for practical purposes is called technology.
- used to find information & solve problems
- contributes to progress of science
Lesson 3 – Models and Simulations
How do scientists use models & simulations?
By the end of this lesson, you should be able to explain how scientists use models and simulation to
represent systems, explain phenomena, and make predictions.
- model – shows the structure of an object, system, or concept
- used to represent complex real world interactions
- can be used to make predictions that affect daily lives (ex. weather model)
- simulations – use models to imitate the function, behavior, or process of whatever the models represent
- physical model – represents the physical structure of an object or system (ex. toy car represents real
car)
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- study objects or systems too small to see or too big to see completely
- used when objects too far away, too dangerous, too expensive to study, or no longer exist
- don’t always behave like the real thing
- easier and safer to work with than the real thing
scale models are used to estimate distance, volume, or quantity
scale – relationship between a model’s measurements and the real object’s measurements
life size model – same size as real object; used to study objects that are rare or are difficult to find in
natural world
mathematical model – uses different forms of data to represent the way a system or process works
- made up of numbers and equations
- often shown as graphs & used to predict future trends
- easy to change and adjust
- some systems or situation are too complex to model easily and may contain errors
- based on current data and may not be useful in the future
conceptual model – representation of how parts of a system are related or organized
- used to simplify complex relationships like identifying patterns & similarities for classification
- ex. periodic table – elements are horizontal rows have same number of electron shells with
elements in vertical rows having similar chemical properties
- can be used to represent processes that cannot be directly observed - ex. rock cycle
simulations use models to show how an object or system works
- used to improve the performance of a piece of technology
- helps with quality control, safety, training, and education
- in research, simulations allow scientists to control variables when conducting tests and to
determine what happens when variables are changed