Chapter Two Study Guide - Council Rock School District



Chapter Two Study Guide

The Work of Scientists

Metric System: International System of Units (SI)

← Based on the number 10 and multiples of 10

| | | |BASE | | | |

|Kilo |Hecto |Deca | Meter |Deci |Centi |Milli |

|(k) | (h) | (da) | Liter | (d) | © | (m) |

Gram

Mass: A measure of the amount of matter an object contains

• Basic Unit of Mass: kilograms

• Tool: Triple Beam Balance

[pic]

• 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 [pic]

Metric Ruler

• Meniscus: curved top surface of a liquid; we read the bottom of the curve

• Formulas:

▪ Volume of a regular solid: L x W x H

▪ 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 100%

True value

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

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