Measuring in SI

The metric system of measurement was developed in 1795. A modern form of the metric system, called the International System, or SI, was adopted in 1960. SI provides standard measurements that all scientists around the world can understand.
The metric system is convenient because unit sizes vary by multiples of 10. Prefixes are used to name units. Look at the table below for some common metric prefixes and their meanings. Do you see how the prefix kilo- attached to the unit gram is kilogram, or 1,000 g?

Measuring Length
Now look at the metric ruler on your desk. The centimeter lines are the long, numbered lines, and the shorter lines are millimeter lines. When using a metric ruler, line up the 0-cm mark with the end of the object being measured, and read the number of the unit where the object ends.

Liquid Volume
The unit that is used to measure liquids is the liter. A liter has the volume of 1,000 cm?. The prefix milli- means "thousandth (0.001)." A milliliter is one thousandth of 1 L and 1 L has the volume of 1,000 mL. One milliliter of liquid completely fills a cube measuring 1 cm on each side. Therefore, 1 mL equals 1 cm.

Beakers and graduated cylinders are used to measure liquid volume. The surface of liquids is always curved when viewed in a glass cylinder. This curved surface is the meniscus. A meniscus must be looked at along a horizontal line of sight as in the picture below. A graduated cylinder is marked from bottom to top in milliliters. This graduated cylinder contains 79 mL of a liquid.

Graduated cylinders measure liquid volume

Mass
Scientists measure mass in grams. You will use a beam balance similar to the one shown below. The balance has a pan on one side and a set of beams on the other side. Each beam has a rider that slides on the beam.


A triple beam balance is used to determine the mass of an object.

Before you find the mass of an object, slide all the riders back to the zero point. Check the pointer on the right to make sure it swings an equal distance above and below the zero point. If the swing is unequal, find and turn the adjusting screw until you have an equal swing.

Place an object on the pan. Slide the largest rider along its beam until the pointer drops below zero. Then move it back one notch. Repeat the process on each beam until the pointer swings an equal distance above and below the zero point. Sum the masses on each beam to find the mass of the object. Move all riders back to zero when finished.
You should never place a hot object on the pan or pour chemicals directly onto the pan. Instead, find the mass of a clean container. Remove the container from the pan, then place the chemicals in the container. Find the mass of the container with the chemicals in it. To find the mass of the chemicals, subtract the mass of the empty container from the mass of the filled container.

Metric Conversions

Some things to Remember when converting any type of measures:
To convert from a larger to smaller metric unit you always multiply To convert from a smaller to larger unit you always divide
The latin prefixes used in the metric system literally mean the number they represent. Example: 1 kilogram = 1000 grams A kilo is 1000 of something just like a dozen is 12 of something.
This is the metric conversion stair chart. You basically take a place value chart turn it sideways and expand it so it looks like stairs. The Latin prefixes literally mean the number indicated. Meter, liter or gram can be used interchangeably.
You use this chart to convert metric measurements like this:
If you are measuring length use meter.
If you are measuring dry weight use grams.
If you are measuring liquid capacity use liter
For every step upward on the chart you are dividing by 10 or moving the decimal one place to the left.. Example: To convert 1000 milligrams to grams you are moving upward on the stairs: Pretend you are standing on the milli-gram stair tread and to get to the 1-gram stair tread you move up 3 steps dividing by 10 each time. 1000/10 = 100 100/10 = 10 10/10 = 1 or
1000/1000 = 1 or use the shortcut and just move the decimal place one place to the left with each step
1000 milligrams = 1 gram.
When you move down the stairs you are multiplying by 10 for each step. SO you are adding a zero to your original number and moving the decimal one place to the right with each step. Example: To convert 2 kilometers to meters you move 3 steps down on the chart so you add 3 zeros to the 2. 2 kilometers = 2000 meters

Scientific Method

How can we determine if something is a fact or an opinion? How can we determine an answer to a problem? The answer is use the scientific method.

What is the Scientific Method? It is a series of steps used to help solve a problem.

• 1. Define the problem. Make sure only one problem is beingstudied.
• Step 2. Research the problem. Use all available resources to collect data on the subject being covered. Libraries, Internet, books, magazines, personal interviews, etc.
• Step 3. Develop a hypothesis (educated guess). Make it a short definitive statement. It should be an "if then" statement. The "if part will become the hypothesis and the then part should be the results received at the end of the controlled experiment. Remember your hypothesis can be changed it is not formed in concrete.
• Step 4. Develop a controlled experiment. A controlled experiment is an experiment that contains only one experimental variable. An experimental variable is the thing being tested. Everything else in the experiment or all other variables must be the same. These variables are also called the controlled variables. Keeping these variables the same allows the experimenter to show that it was the experimental variable that caused the results.
• 5. Analyze the data and come up with a conclusion. Theconclusion may or may not support the hypothesis. Additionalexperimentation must then take place to build documentationconcerning the problem. If the hypothesis is proven wrong, changethe hypothesis, not the data.

Graphing

Choosing the Right Graph

A BAR GRAPH is best used for comparing data quickly and easily, such as the grade distribution of students enrolled in science class.

A PIE GRAPH is best used for showing percentages, such as the percentage of th student body who picked certain entrees for lunch.

A LINE GRAPH is best used for looking at changes over time, such as the number of bathing suits sold each month during the year.

CREATING GRAPHS

*First, set up your graphs with an x-axis and a y-axis. The x-axis is horizontal and the y-axis is verticle. The axes represent different variables in an experiment.
*The x-axis represents the independant variable. The independent variable is the variable whose values are chosen by the experimenter. For example, the range of grades is the independant variable.
*The y-axis represents the dependent variable. The values for the dependaent variable are determined by the independent variable. If you are grouping students by grades, the number of students in each group depends on the grade they get.
*Next, choose a scale for each of the axes. Select evenly spaced intervals that include all of your data. When you label the axes, be sure to write the appropriate units where they apply.
*Next, plot your data on the graph. Make sure you double-check your numbers to ensure accuracy.
*Finally, give your graph a title. A title tells the reader what he or she is studying. A good title should explain the relationship between the variables. Your graph is then complete.