si – international system of units

SI - (AKA International System of Units or S.I.) is a measuring system based on units of 10.

Math – the language of scienceUnits in the S.I. are: meter (m), which is used for measuring

length. liter (l), which is used to measure volume.

* gram (g), which is used to measure mass.

SI – International System of Units

Kilo (k)

Hecto (h)

Deka (de) or deca (da)

Base Unit (m, l, or g)

Deci (d)

Centi (c)

Milli (m)

1000

100

10

1 0.1

0.01

.001

1000/1 100/1 10/1

1

1/10

1/100 1/1000

SI (metric) prefixes

STOP DO NOT WRITE UNTIL I TELL YOU TO The three prefixes that we will use the

most are:◦ kilo◦ centi◦ milli

kilo hecto deca

Base Unitsmete

rgramliter

deci centi milli

These prefixes are based on powers of 10. What does this mean?◦From each prefix every “step” is

either: 10 times larger

or 10 times smaller

◦For example Centimeters are 10 times larger than

millimeters 1 centimeter = 10 millimeters kilo hecto deca

Base Unitsmetergramliter

deci centi milli

An easy way to move within the metric system is by moving the decimal point one place for each “step” desired (swoop method)Example: change meters to centimeters

1 meter = 10 decimeters = 100 centimetersor1.00 meter = 10.0 decimeters = 100. centimeters

kilo hecto decameterliter

gramdeci centi milli

If you move to the left in the diagram, move the decimal to the left

If you move to the right in the diagram, move the decimal to the right

kilo hecto decameterliter

gramdeci centi milli

YES WRITE THESE NOTES: Summary

◦ Base units in the SI (metric system) are meter, liter, gram

◦ Metric system is based on powers of 10◦ For conversions within the SI, each “step” is 1

decimal place to the right or left◦ Using the diagram below, converting to the right,

moves the decimal to the right and vice versa

kilo hecto deca

BASE UNITSmeterliter

gram

deci centi milli

Practice problems:

Base SI UnitsQuantity Unit Symbol

Length meter mMass kilogram kgTemperature kelvin KTime second sAmount of Substance

mole mol

Luminous Intensity

candela cd

Electric Current ampere a

Other - SI Unit PrefixesName Symbolgiga- G 109

mega- M 106

kilo- k 103

deci- d 10-1

centi- c 10-2

milli- m 10-3

micro- μ 10-6

nano- n 10-9

pico- p 10-12

Derived SI Units (examples)

Quantity unit Symbol

Volume cubic meter m3

Density kilograms per cubic meter

kg/m3

Speed meter per second m/s

Newton kg m/ s2 N

Energy Joule (kg m2/s2) J

Pressure Pascal (kg/(ms2) Pa

Units for Volume m3

cm3

L

mL

When do you use m3 ? irregular objects?

1cm3= 1mL

Tools for measuring:

1. Using a RulerCentimeters and Millimeters

1. Begin on the 1cm mark and make your recording.2. Subtract 1 from the number your recorded to get your answer. For example: 1.5cm - 1.0 cm = 0.5 cm Make sure you include 1 digit after the

decimal. This is usually an estimate.

How to use a metric ruler

3.85 cm - 1.0 cm = 2.85 cm

Let’s Practice

◦ Centimeters are 10 times larger than millimeters so it takes more millimeters for the same length

1 centimeter = 10 millimeter

1 mm

1 mm

1 mm

1 mm

1 mm

1 mm

1 mm

1 mm

1 mm

1 mm

1 cm

4 00

41

411

40

1. Place the graduated cylinder on a flat surface.2. Read from the bottom of the meniscus (bubble) at EYE LEVEL.3. Again you want to estimate.

2. Graduated cylinder

How to read a graduated cylinder

Graduated Cylinder - Meniscus

1. Move all sliders/masses to the left.

2. Check to see if the mark on the moving arm

lines up with the 0 on the balance.

3. Place specimen on pan then move the sliders

until the marks line up at 0.

3. Triple – beam balance

How to use a triple-beam balance

Let’s Practice

1. Place the electronic balance on a flat, stable surface indoors. 2. Press the "ON" button and wait for the balance to show zeroes on the digital

screen.3. Use a container for your object to be massed (never place directly on the

balance).4. Press the "Tare" or "Zero" button to automatically deduct the weight of the

container from future calculations. The digital display will show zero again, indicating that the container's mass is stored in the balance's memory.

5. Carefully add the substance to the container. Ideally this is done with the container still on the platform, but it may be removed if necessary. Avoid placing the container on surfaces that may have substances which will add mass to the container such as powders or grease.

6. Place the container with the substance back on the balance platform if necessary and record the mass as indicated by the digital display

4. Digital BalanceHow to use a digital balance

Picture here,..

Why do we use the SI/Metric System?

To making accurate and precise measurements.

Percent Error

% Error= |experimental –accepted| x100

accepted value