SI – International System of Units

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# SI – International System of Units - PowerPoint PPT Presentation

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 science Units in the S.I. are: meter (m), which is used for measuring length. liter (l), which is used to measure volume. *

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## SI – International System of Units

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Presentation Transcript
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 science

Units in the S.I. are:

• meter(m), which is used for measuring length.
• liter (l), whichis used to measure volume. *
• gram (g), whichis used to measure mass.
STOP DO NOT WRITE UNTIL I TELL YOU TO 
• The three prefixes that we will use the most are:
• kilo
• centi
• milli
• 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
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 centimeters

or

1.00 meter = 10.0 decimeters = 100. centimeters

• If you move to the right in the diagram, move the decimal to the right
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
m3

cm3

L

mL

When do you use m3 ? irregular objects?

1cm3= 1mL

Units for Volume
How to use a metric ruler

1. Begin on the 1cm mark and make your

recording.

2. Subtract 1 from the number your recorded

1.5cm - 1.0 cm = 0.5 cm

• Make sure you include 1 digit after the decimal. This is usually an estimate.
Let’s Practice
• 3.85 cm - 1.0 cm = 2.85 cm
Centimeters are 10 times larger than millimeters so it takes more millimeters for the same length

1 centimeter = 10 millimeter

4 00

411

40

41

1 cm

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.

3. Triple – beam balanceHow to use a triple-beam balance

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.

4. Digital BalanceHow to use a digital balance

1. Place the electronic balance on a flat, stable surface indoors.

• Press the "ON" button and wait for the balance to show zeroes on the digital screen.
• Use a container for your object to be massed (never place directly on the balance).
• 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.
• 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.
• Place the container with the substance back on the balance platform if necessary and record the mass as indicated by the digital display

### Why do we use the SI/Metric System?

To making accurate and precise measurements.

Percent Error

% Error=|experimental –accepted| x100

accepted value