Name ______Date ______Hour _____
SI UNITS OF SCIENCE
(AKA METRICS)
Scientists all over the world use one system of measurement. This system is called the metric system. The official name of the metric system is Systeme Internationale d’Unites (international system of units), but is commonly abbreviated as SI.
The basic units of the SI system are meter, liter, and gram.
· The meter is used for linear measurements or measurements of length. In the United States, inches, feet, yards, or miles are commonly used for linear measurements. The symbol for meter is m.
· The liter is used for measuring volume. Today, in the United States, soft drinks are sold in liters instead of ounces, pints, quarts, or gallons. The symbol for liter is L.
· The gram is used to measure mass. The units on a triple beam balance are given in grams instead of ounces or pounds. The symbol for gram is g.
The metric system adds prefixes to these base units to make smaller or greater measurements. The prefixes are shown in the following table.
PREFIX / PREFIX MEANING / ABBREVIATIONLength Mass Volume
giga / 1 billion times the base unit / G / Gm / Gg / GL
mega / 1 million times the base unit / M / Mm / Mg / ML
kilo / 1000 times the base unit / k / km / kg / kL
hecto / 100 times the base unit / h / hm / hg / hL
deka (deca) / 10 times the base unit / da / dam / dag / daL
meter, gram, or liter / Base unit / m / g / L
deci / 1/10 of the base unit / d / dm / dg / dL
centi / 1/100 of the base unit / c / cm / cg / cL
milli / 1/1000 of the base unit / m / mm / mg / mL
micro / 1 millionth of the base unit / µ / µm / µg / µL
nano / 1 billionth of the base unit / n / nm / ng / nL
These prefixes can be added to any of the metric base units. For example, the base unit for length is the meter. To measure smaller lengths, scientists can use centimeters. Based on the definition for centi, which is 1/100 of the base unit, a centimeter is 1/100 of a meter. There are 100 centimeters in a meter. The prefixes mean the same things no matter which base unit is being used. One kilogram would be 1000 times the base unit, which is the same as 1000 grams.
USING SI UNITS
Underline the root word (basic unit) for each of the following:
1. kilogram 4. millimeter
2. decimeter 5. decagram
3. hectometer 6. centimeter
Underline the prefix for each of the following:
1. kilogram 4. hectometer
2. deciliter 5. milligram
3. decameter 6. centiliter
Write the symbols for the following:
1. kilogram 4. decagram
2. deciliter 5. millimeter
3. hectometer 6. centiliter
Use the correct units to complete the story below.
Mary Metric went to a football game. She arrived late and had to sit on a narrow 15 centi______bench. She cheered as the quarterback threw a magnificent 50 ______pass. Mary saw the large, 100 kilo______guard sack the quarterback. All this activity made Mary very thirsty. She bought a 0.5 ______cola to quench her thirst. After the game, Mary had to walk one kilo______to get to her car. She arrived at her car only to find it stuck in a puddle with about 5.5 deca______of water. Mary knew she had to hurry home if she wanted to make her curfew. Luckily the football team came by and pushed the 7,000 kilo______car out of the mud. Mary felt the car hesitate and realized that she was out of gas. She stopped at the Jiffy store and added 7 ______to her gas tank. Mary finally made it home, but was met at the door by her parents, who grounded her for being late. She also had to shovel 100 kilo______of manure onto their garden for expecting them to buy this alibi.
FINDING LENGTH
To measure length, we use a tool called a meter stick. For shorter lengths, a tool called a metric ruler can be used. Below you see a sample of the scale you will see on both the meter stick and the metric ruler. The length of an entire meter stick is one meter. It is divided into 100 parts called centimeters. A centimeter = .0l meter. These are the longer marks on the meter stick. They are usually numbered. The smallest marks on the meter stick are millimeters. There are 1,000 of these marks on each meter stick. A millimeter = .001 meter. Each centimeter is equal to ten millimeters. You could also say that a millimeter = .1 centimeter.
Notice that the line measures more than 5, but less than 6 centimeters. If you were to measure this line to the nearest centimeter, You would say it is 6 centimeters long since it is closer to 6 cm than 5 cm. This is not very precise, however. You might say that the line measures 5 cm and 7 mm, but this is not convenient to record and it is considered bad form to mix metric units. Since each millimeter equals .1 cm, you might say that the line is 5.7 cm long. You might also say that the line is 57 mm long since there are 10 millimeters in each centimeter. Either way, you would be correct. Let’s see if you understand how to use a metric ruler to measure length.
DRAWING LENGTHS – Draw line segments the following lengths.
1. 64 mm
2. 13.5 cm
3. 10 cm 3 mm
4. 0.08 m
5. Draw a line two inches long and measure it to the nearest tenth of a cm. Include units with your answer.
MYSTERY OBJECT – Using the direction below, draw the mystery object.
1. Toward the bottom of this page, draw rectangle 1 with 27 mm sides and a 75 mm top and bottom.
2. Centered on the top of rectangle 1, draw a trapezoid with 24 mm sides, a 75 mm bottom, and a 40 mm top.
3. Centered in the right half of rectangle 1, draw rectangle 2 (see step four for dimensions) so it rests on the bottom line of rectangle 1 10 mm from the right side.
4. Draw rectangle 2 with 17 mm sides and a 12 mm top and bottom.
5. Centered in the left half of rectangle 1, draw rectangle 3 measuring 2 cm2.
6. Centered on the top line of your trapezoid, draw a square measuring 1 cm2.
MEASURING LENGTH
On the illustration below, find the length of the numbered lines. Place your answers on the lines below. Answers must be given in millimeters and centimeters.
Measurement # / Length in cm / Length in mm / Measurement # / Length in cm / Length in mm1 / 6
2 / 7
3 / 8
4 / 9
5 / 10
FINDING VOLUME –
VOLUME OF A FLUID
Earlier you were told that in science, we measure volume in liters. Volume is the amount of space occupied by matter. Usually when we think of volume, we think about liquids. There are other ways of calculating volume which will be discussed later.
To measure liquid The volume we use of a beaker or liquid is calculated by placing the liquid in a container (beaker, flask, graduated cylinder. The marks on these containers that indicate the number of milliliters are called graduations. When measuring a liquid in one of these containers, you should view the liquid at eye level as shown in the diagram. If you are using a graduated cylinder made of glass, you will notice that the upper surface of the liquid is curved or crescentshaped. This curved surface is called a meniscus. The liquid volume should be read from the bottom of the meniscus. A plastic container will not have a meniscus. The volume is simply read from the level of the liquid. The volume of the liquid in the diagram is 35 mL., etc.) which has marking for measuring. Some containers measure more accurately than others as you will observe in the examples below. In science, fluids are usually measured in kL, L, or mL.
You will notice that some containers measure more accurately than others as you will observe in the examples below. In the diagram above, the difference between one graduation and the next is two. This is known as the scale of the graduated cylinder. Determine and record the scale and correct volume for each example below. Make sure you include the correct unit when measuring the volume.
A B C D
Grad Cyl / A / B / C / DScale
Volume
A B C
Beaker / A / B / CScale
Volume
1. Which graduated cylinder measures liquids more accurately based on the scale you found for each one?
2. Which beaker measures liquids more accurately based on the scale you found for each one?
3. Is a graduated cylinder or a beaker more accurate or precise? Explain.
FINDING VOLUME – VOLUME OF A SOLID
To calculate the volume of a solid object, there are two methods. The first method is usually used to determine the volume of objects with geometrical shapes. To find the volume using this method, you would need to measure the dimensions of the object.
When calculating area (two dimensions), you multiply length and width (length x width). To calculate volume, you must add the measurement of a third dimension. The third dimension is called height. Therefore, when determining the volume of an object, you must multiply length, width, and height (length x width x height). The unit of volume for this method is cm3 (cm x cm x cm = cm3).
Using the information you just read: label the length, width, and height. Then, calculate the volume of the box. Show your work. Don’t forget to include the correct unit.
Volume = ______
One thing to take note of is that it takes one milliliter to fill one cubic centimeter of space (1 cm3 = 1 mL). This means that these units are interchangeable.
FINDING VOLUME – VOLUME OF AN IRREGULAR SHAPED SOLID
How could you find the volume of the object (sphere) above? When you are trying to find the volume of an incomplete geometric shape such as the sphere above, there are two methods that can be used. The first is based on pure mathematical calculations. The second is called displacement. In science, we most often use displacement to find the volume of these irregular shaped objects.
When you place an object in a container of liquid, the level of the liquid rises. This happens because the object, which takes up space, pushes the water upward in the container. The amount of water that is displaced (rises upward) represents the volume of the object. The unit for this volume is often mL.
Using the information you just read, find the volume of the object below. Don’t forget to include the correct units.
Initial Volume (Liquid Only) / Final Volume(Liquid plus Object) / Difference
(Object Only)
CALCULATING MASS
It is important to know that there is a difference between mass and weight. Mass refers to the amount of matter an object has. Weight refers to the amount of force gravity exerts on an object. For most practical purposes the two are interchangeable and are treated as if they are the same, but it is important to keep in mind that there is a difference. As you know, the basic unit of mass is grams.
You will be using a triple beam balance to determine the mass of substances in class. It is called a triple beam balance because it has three beams or arms that support rider masses. The rider masses are moved horizontally until the pointer indicates that the mass of the riders and the substance are the same.
Each rider represents a different multiple for the basic unit gram. The larger rider usually represents increases of 100 grams per notch and is located at the back. The center beam usually has the rider that represents increases of 10 grams per notch. The third beam, usually has a rider that indicates both grams and decigrams. The grams are marked with number and the decigrams are the small lines in between. Remember that 1 gram = 10 decigrams.
The disc that holds the substance being massed is called the pan. The level indicator (pointer) is attached to the beams at the end opposite the pan. The level indicator moves vertically along the scale. When the level indicator is at zero on the scale, this indicates the balance is ready for use. Before you begin, use the zero adjusting knob to set the level indicator at zero if it is not already there. The zero adjusting knob will be located somewhere under the pan (ask your teacher if you are not sure).
Based upon what you just read, correctly label the parts of the triple beam balance pictured below.
USING THE TIPLE BEAM BALANCE
To find the mass of a substance, you will use the following steps.