In science class there are NO NAKED NUMBERS- make them appropriate with a unit!
5.
Precision Vs. Accuracy
Precision is how closely repeated measurements match each other .
If you can measure something 1000 times and every time you get the same measurement, you are precise.
Accuracy is how closely a measurement matches the correct or expected value .
If you measure something very closely to the measurement that it is supposed to be, you are accurate.
A ball player's height can be measured precisely, but still not be accurate.
6.
How tall is that horse?
In the past it was common to measure the height of a horse in hands.
Measure the height of your desk in hands and write it below:
Is this a good system for measuring?
7.
The International System of Units
ALL SCIENTISTS us the International System of Units.
We abbreviate it as SI.
Some good things about measuring in SI:
It is based on multiples of 10 .
There are no fractions- we use decimals in the metric system.
All scientists use the International System of Units.
8.
Who uses the SI system?
In everyday life, just about everyone except for US!
These countries do not use the metric system:
The United States of America
Liberia
Myanmar
ALL SCIENTISTS IN THE WORLD USE THE SI SYSTEM OF MEASUREMENT!
9.
What are prefixes?
Pre means “before”
A prefix is a small part of a word that comes before the word.
Metric prefixes equal a number.
10.
Common Metric Prefixes 0.000 000 001 or 10 -9 n nano- 1 000 000 000 or 10 9 G Giga- 1 000 000 or 10 6 M Mega- 0.001 (one thousandth) m milli- 0.01 (one hundredth) c centi- 0.1 (one tenth) d deci- 10 da deka- 100 h hecto- 1000 k kilo- Meaning Symbol Prefix
11.
12.
How can you put those numbers in your calculator?
Try these:
10 4
10 -4
10 -2
10 2
10 3
13.
Adding prefixes
When we measure, we can add a prefix to change the value.
1 nanosecond = how many seconds?
Find nano- on your chart.
What does it mean?
1 nanosecond = 10 -9 seconds
1 kilometer = 1000 meters
1 milligram = 0.001 grams
14.
Rules for writing metric symbols
Do not use a period.
7 s [not 7sec.]
Leave a space.
6 kg [not 6kg]
Do not add an s to the symbol.
10 Kilometers = 10 km [not 10 kms]
Do not capitalize, unless it is supposed to be capital.
Milliliter = ml [not Ml]
Do not use p for per.
miles per hour = mi/hr [not mph]
15.
Write the correct units
mm = millimeter
mg = milligrams
L = liter
Mg = Megagram
m = meter
dam = decameter
g = gram cm = centimeters ns = nanosecond
16.
Which number is bigger?
4 cm or 4 hm
10 km or 10 mm
12g or 12 kg
17.
What will we measure?
Length
Distance between two points.
Mass
Amount of material in an object.
Temperature
Amount of heat a material has.
Volume
Amount of space an object takes up.
18.
What are BASE UNITS?
A base unit is the standard unit of measurement that we will use to measure .
We will add prefixes to the base units .
19.
Measuring LENGTH
The SI base unit of measurement for length is the METER .
1 meter = 1m
Your desk is about one meter tall.
You can use a METRIC RULER or a METERSTICK to measure length.
20.
21.
Other units of length
If you wanted to measure between cities, you would use KILOMETERS.
A kilometer is equal to 1,000 meters.
If you wanted to measure small lengths, you would use a centimeter or a millimeter.
There are 100 cent imeters in a meter.
Just like there are 100 cent s in a dollar.
There are 1000 millimeters in a meter.
22.
SURFACE AREA
Surface area is the space that a surface covers.
If you wanted to buy carpet or floor tile, you will have to know the SURFACE AREA of the floor.
23.
Calculating SURFACE AREA
To find the area of a rectangle, multiply length X width.
AREA = Length X Width
What is the area of this rectangle?
10cm
5cm
A = L X W
= 10 cm X 5 cm
= 50 cm 2
24.
Practice!
How much carpet do you need to cover the floor in a room that measures 7 meters long and 5 meters wide?
L = 7 m
W = 5 m
A = L X W
A = 7 m X 5 m
A = 35m 2
25.
26.
Measuring VOLUME of a liquid
The SI base unit of measurement for volume is the LITER .
1 Liter = 1L
You will use different units and tools to measure volume of a liquid or a solid.
You can use a GRADUATED CYLINDER to measure the volume of a liquid.
27.
28.
Graduated cylinders measure in mL or milliliters.
The plastic ring around a graduated cylinder prevents breaking.
To read a graduated cylinder:
Move to eye level.
Read the bottom of the meniscus .
29.
How much water is in this graduated cylinder? Image from ChemPages Laboratory Resources http://jchemed.chem.wisc.edu/JCESoft/Programs/CPL/Sample/modules/gradcyl/grad100mL.htm
30.
VOLUME of a solid
If you are trying to find the volume of a solid, you cannot pour it into a graduated cylinder.
Methods:
Water displacement
Calculating volume
31.
Water Displacement
32.
What steps will you take to measure with water displacement?
Put water in the graduated cylinder.
Record the measurement.
Tilt the graduated cylinder to the side.
Gently lower the object into the graduated cylinder. (Make sure that the whole object is under water.)
Record the measurement.
Water & Object – Water = Object’s volume
REMEMBER 1 ml = 1 cm 3 = 1 cc
33.
Calculating Volume of a Block
To find the volume of a regular (block or box shaped) solid, you need to measure the length, width and height IN THE SAME UNIT and multiply these three numbers together. V= L X W X H
What is the volume of the black cube?
What is the volume of the bigger cube?
Volume = length X width X height
V = 3 cm X 2 cm X 2 cm
V = 12 cm 3
34.
Units of VOLUME
1 liter = 1 L
1 milliliter = 1 mL
1 centimeter cubed = 1 cubic centimeter = 1 cm 3 = 1 cc
1 L = 1000 mL
1 mL = 1 cm 3
1 L = ___________cm 3
35.
36.
Measuring MASS
The SI base unit of measurement for mass is the GRAM .
1 gram = 1g
A paperclip is about 1 gram.
You can use a TRIPLE BEAM BALANCE or an ELECTRONIC SCALE to measure mass.
37.
38.
Using an electronic balance
They are very sensitive.
DO NOT place heavy objects or press down with your hand.
DO NOT put liquid, powder or crystals directly on the tray.
39.
Other units of mass
If you wanted to measure large masses you would use KILOGRAMS.
1 Liter of pop has a mass of about 1 kilogram.
If you wanted to measure the mass of smaller objects, you would use milligrams or centigrams.
When have you heard someone say milligrams?
40.
41.
Measuring TEMPERATURE
The SI base unit of measurement for temperature is Kelvin (K) .
A more common unit is DEGREES CELSIUS.
1 degrees Celsius = 1ºC
You can use a THERMOMETER to measure temperature.
42.
43.
Look at the picture to compare ºF and ºC.
44.
45.
Measuring TIME
The SI base unit of measurement for time is the SECOND .
1 second = 1s
We will use a STOPWATCH to measure time in science class.
46.
Time (s)
47.
How do you change from one unit to another?
From another system to metrics or changing metrics FACTOR LABEL METHOD .
From metrics to metrics, MOVE THE DECIMAL.
48.
from Industry Week , 1981 November 30
49.
FACTOR LABEL METHOD
Write down what you know.
Write down what you know about those two units.
Multiply by a fraction.
Cancel out like units.
Do the math.
50.
Let’s Practice!
600 mm = ? m
1 m = 1000 mm or 1 mm = 0.001 m
600 mm X 1 m = 0.6 m
1000 mm
51.
0.35 liters = ? milliliters
52.
1050 grams = ? kilograms
53.
4 years = ? days
54.
20 kilograms = ? milligrams
55.
3500 seconds = ? hours
56.
Moving the decimal Metric unit conversion is simply a matter of moving the decimal in the correct direction and the correct number of places.
57.
Write this chart:
Find the unit you are starting with.
Find the unit you want to change to.
Count the number of spaces you have to move.
Which way did you move?
Move the decimal in that direction that number of spaces.
10 -3
10 -2
10 -1
10 1
10 2
10 3
0.001 0.01 0.1 gram (g) meter ( m) liter (L) second (s) 10 100 1000 m c d da h k milli centi deci BASE UNIT deca hecto kilo
58.
Convert these:
35 ml = ? dl
2000 mm = ? km
0.752 hg = ? cg
10 -3
10 -2
10 -1
10 1
10 2
10 3
0.001 0.01 0.1 gram (g) meter ( m) liter (L) second (s) 10 100 1000 m c d da h k milli centi deci BASE UNIT deca hecto kilo
59.
How can we remember the order of the chart?
K ids H ave D ropped OVER D ead C onverting M etrics