Chapter Two Study Guide
The Work of Scientists
Metric System: International System of Units (SI)
 Based on the number 10 and multiples of 10
Kilo
(k)
Hecto
(h)
Deca
(da)
BASE
Meter
Liter
Gram
Deci
(d)
Centi
©
Milli
(m)
Mass: A measure of the amount of matter an object contains
Basic Unit of Mass: kilograms
Tool: Triple Beam Balance
Measures in grams
Mass = Weight
Weight is a measure of the force of gravity acting on an object
Volume: The amount of space an object takes up
Basic Unit of Volume: liter
Tool: Graduated cylinder
Metric Ruler
Meniscus: curved top surface of a liquid; we read the bottom of the curve
Formulas:
 Volume of a regular solid:
LxWxH
 Volume of an irregular solid: Vf (final volume) –Vi (initial volume)
Density: The quantity of mass contained in a given volume
All substances have a specific density
The size of an object does not change the density because as size increases so
does volume.
Basic Units of Volume: g/ml or g/cm
Tools: Triple Beam Balance (mass)
Graduated Cylinder (volume) or
Metric Ruler (volume)
Density of water = 1.0g/ml
Temperature: The measurement of how hot or cold something is
SI Unit: Kelvin (K)
Tool: Thermometer – we use
Celcius
Mathematics and Science
Estimation: an approximation of a number based on reasonable assumptions
Scientists rely on estimates when they can not obtain exact
Numbers
Accuracy and Precision
Accuracy: how close a measurement is to the true or
accepted value
Precision: how close a group of measurements are toe each other
Significant Figures: all the digits in a measurement that have been measured
exactly, plus one digit whose value has been estimated.
Rule for Adding or Subtracting significant figures
1. The answer can have only as many figures after the decimal point as the
measurement with the fewest figures after the decimal
Example: 5.3 cm (1 significant figure after the decimal)
+ 21.94 cm (2 significant figures after the decimal)
27.24 cm = 27.2 cm (b/c 5.3 has only 1 sig fig after the
decimal point)
Rule for Multiplying or Dividing significant figures
1. When multiplying or dividing, the answer can only have the same number of
significant figures as the measurement with the fewest significant figures.
Example: 2.25 m (3 significant figures)
X 3 m (1 significant figure)
6.75 m = 7m (1 significant figure)
The answer has 1 significant figure because the least precise
measurement (3 meters) has one significant figure
Percent Error: a calculation used to determine how accurate or close to the true
value an experimental value really is.
1. Formula to calculate Percent Error
Experimental value – True value
True value
100%
Low Percent Error: very accurate results
High Percent Error: not very accurate results
Mean, Median, Mode
Mean: numerical average
1. To find the mean: Add up all the numbers and divide by the total number
of items.
Example: 110 102 110 107 109 110 94
94+102+110+107+109+110+110 =742
742 7 = 106 (the average)
Median: middle number in a set of data; to find the median place all numbers in
order from smallest to largest
Odd number of entries: median is middle number
Even number of entries: median is two middle numbers added
Together and divided by 2
Example: 94 102 110 107 109 110 94 110
Order numbers:
94 102 107 109 110 110 110
Odd amount of numbers, 109 middle number
Mode: number that appears the most often in a list of numbers
Example: 94 102 107 109 110 110 110
Mode = 110 (110 occurs 3 times)
Graphs: a graph is a picture of your data which shows us patterns or trends
Graphs
1. Line Graph: shows how the responding variable changes in response to the
manipulated variable.
Parts of a Graph
1. Horizontal Axis: graph line that runs left to right
2. Vertical Axis: graph line that runs up and down
3. Origin: the point where the x-axis and y-axis cross
4. Coordinate: a pair of numbers used to determine the position of a point
on a graph
5. Data point: the point showing the location of a piece of date
6. Line of best fit: shows the overall trend in the data
**When no trend is identifiable in a graph there is not
relationship between the two variables.
7. Slope: the steepness of the graph line; the ratio of the vertical
Change (rise) to the horizontal change (run)
**Formula**
Slope = Rise = Y - Y
Run
X - X
Example:
Two coordinates (20,10)
(50,25)
Slope = 25-10 = 15 = 0.5
50-20
30