Measurement and Graphing

Standard of Measurement

A standard is an exact quantity that people agree to use as a basis of comparison

SI - The International System of Units

Most of the world, and science, uses the SI - international system of units

SI uses standard prefixes, based on powers of 10

Metric Units Length - meter (m) Capacity (liquid measure) - liter (l) Weight - gram (g) Pressure - bar (b) Temperature

Celsius (°C) Kelvin (K)

Basic Units Are Designated by the Following Prefixs:

Kilo-1000 hecto-100 deka-10 Meter-1 deci-0.1 centi-0.01 milli-0.001

Metric Conversion Stair Chart

Measuring Liquids Reading a graduated cylinder:

A graduated cylinder is used to find the volume of a liquid

The marks on the cylinder are called graduations

Each mark on this cylinder is worth one milliliter

MeniscusWhen a liquid is put

into a cylinder, the surface curves

This curve is called a meniscus

When reading the volume of a liquid, always read at the bottom of this curve while holding the surface at eye level

The lettered arrows on the diagram to the left point to volume measurements. Arrow "A" reads 48 ml.

What are the answers to the other arrows?

Measuring Mass With a Triple-beam Balance

As you face the balance, the back beam is graduated in 10 gram steps

The middle beam is graduated in 100 gram steps The front beam is a sliding scale graduated in

grams

Reading a Thermometer Temperature is measured using an

instrument called a thermometer To read accurately your eyes

should be level with the top of the liquid in the tube

Handling the thermometer can affect its reading, as heat transfers from your hands

Graphing Graphs provide pictures of

numerical (number) relationships Scientists often use graphs to

illustrate comparisons or trends (patterns) that they’ve discovered.   The line graph and bar graph are

used most often in biology The type of information being

displayed determines which graph is used

Use a line graph to show a cause and affect relationship between two variables A line graph depicts how x affects y

 The x-axis: the horizontal line  The y-axis: the vertical line 

This line graph shows the average value of a pickup truck versus the mileage on the truck. When the truck is new, it costs $14000. The more the truck is driven, the more its value falls according to the curve above. Its value falls $2000 the first 20000 miles it is driven. When the mileage is 80000, the truck's value is about $4000.

Use a bar graph to show relative magnitudes A bar graph is used to show several comparisons

at once The values on the x-axis do not necessarily mean

an increase in value The x-axis will be what you are trying to compare The y-axis will be the magnitude of what you are

comparing 

The bar chart below shows the favorite cereals of a group of students. We can see that only 2 students prefer Cheerios, while 6 prefer Life.

Types of Variables

Independent variable: the variable set up by the experimenter. It is the variable that you are manipulating to see how the dependent variable changes Only one independent variable can be tested

at a time Plotted on the x-axis

Types of Variables  Dependent variable: the variable you measure

as a result of the independent variable Plotted on the y-axis  

Example: dissolved oxygen is oxygen that is in water that fish can use. You want to find out will happen to the amount of dissolved oxygen when water temperature goes up

  The independent variable is the temperature because

it is what you are going to change to see what happens (x-axis)

  The dependent variable is the amount of dissolved

oxygen (it changes when you change the temperature) (y-axis)

1. Label each axis: indicate on

each axis what is being measured. Include the unit

of measurement For example: temperature

(degrees Celsius) or time (minutes)

2. Include increments on each axis

To determine what increments to use solve this equation

Largest # on the graph line- smallest # on the same line

# Of available line on the graph paper The scale should be chosen so that it is easy to read,

and so that it makes the data occupy more than half of the paper

The zero of a scale does not need to appear on the graph

3. Place independent variable on the x-axis (the axes should be labeled with words and with units)

4. Place dependent variable on the y-axis (the axes should be labeled with words & units)

5. Connect the points or shade the bars

6. Give a title: the title should uniquely identify the graph, be short & descriptive