This presentation is the property of its rightful owner.
1 / 24

# Measurements and Conversions PowerPoint PPT Presentation

Measurements and Conversions. Why Measure?. Measurements give specific information Different types: - Base Units: System International Units (or Metric) Standard for many scientific measurements - Derived Units Combinations of base units Ex: density or volume. Metric Units

Measurements and Conversions

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.

- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -

## Measurements and Conversions

### Why Measure?

• Measurements give specific information

• Different types:

- Base Units: System International Units (or Metric)

• Standard for many scientific measurements

- Derived Units

• Combinations of base units

• Ex: density or volume

Metric Units

Mass – the amount of matter in an object, grams (g)

Volume – the amount of space an object occupies, liter (L)

Length – distance between two points, meter (m)

### Metric Prefixes

• Converting with metric units

• K H D __ d c m

• Place 1 under starting prefix

• Place 2 under ending prefix

• Draw an arrow from 1 to 2. This is the direction to move the decimal point.

• Count the number of places to go from 1 to 2. Be sure to count the __ space.

• Move decimal point and rewrite number.

Make the following metric conversions

13.5 g  ___ kg2.75 mL  ___ L

150 mm  ___cm0.0150 m  ___cm

0.195 cg  ___ mg0.750 L  ___mL

2.46 mg ___ kg5.79 HL  ___ L

7.53 km  ___cm0.0432 g  ___mg

4150 cL ___ L739 dm  ___ m

81.8 cg  ___kg418.2 m  ___ km

• Scientific Notation – a way of showing very large or small numbers.

• 4.7 x 1034.7 E 34.7 exp3

• 4.7 x 10 x 10 x 10 = 4,700

• Only significant numbers remain

• The “number out front” is only allowed to have one nonzero digit to the left of the decimal point.

### Converting TO Scientific Notation

• Place the decimal after the first digit

• Count from the original decimal place to the new location.

• That number will become the exponent.

• If you counted:

• To the left (starting # > 1) then + exponent

• To the right (starting #< 1) then - exponent

• Write “new” number x 10exponent

• Do not write any placeholding zeros

• Non-significant numbers

### Converting FROM Scientific Notation

• The exponent or power tells how many places the decimal point will be moved.

• If the exponent is positive, the decimal point moves to the right.

- The number will be > 1

• If the exponent is negative, the decimal point moves to the left.

- The number will be < 1

### Warm-Up

• Convert the following:

1. 41,300 L to kL

2. 13,200 kg to g

3. 72 cm to mm

• 41.3 kL

• 13,200,000g

• 720mm

### Warm-Up

• Express is Scientific Notation:

• 1600

• 0.0053

• 134.8

1. 1.6 x 103

2. 5.3 x 10-3

3. 1.348 x 102

### Reliability of Measurements

• Exact numbers - counting numbers

- Not measurements

- A stated value that is certain

• Example: 100 years = 1 century, 1 foot = 12 inches

• Measured numbers- have uncertainty because of the equipment/device used and the observer

• ### Accuracy and Precision

• Accuracy

- How close the measured value is to the accepted value

• Precision

- How close a series of measurements are to each other

### Significant Figures

• Scientists use significant figures to show how precisely an experiment was performed

• Significant Figures (sig figs) – all known digits in a measurement plus one estimated digit.

• Scientists use rules to determine the number of significant figures in a particular value

### When to use Sig Fig

• When something is MEASURED

• Not when something is COUNTED

### Coast to Coast Sig Figs

Atlantic/Pacific Rule:

• If a decimal point is absent, count from the Atlantic (right) side starting with the first nonzero digit.

• If a decimal point is present, count from the Pacific (left) side starting with the first nonzero digit

• 47.08020

• 10

• 5400600

• 1.158

• 0.007013

• 100.

### Rounding numbers in calculations

• Add/subtract: the answer will have the same number of places past the decimal point as the measurement with the fewest places past the decimal point.

• Multiply/divide: the answer will have the same number of sig figs as the measurement with the fewest number of sig figs.

• Rounding off numbers: 0-4 drop, 5-9 add 1

• Defined or exact numbers have an infinite number of significant figures.

### WHEN to round off significant figures

• When the rules for rounding change

• i.e. going from addition  division or

• At the end of the problem, and you are giving the final answer

### Conversions that you are responsible for knowing…

• 12 in = 1 ft

• 3 ft = 1 yd

• 5280 ft = 1 mile

• 60 sec = 1 min

• 60 min = 1 hr

• 24 hr = 1 day

• 7 day = 1 wk

• 365.25 days = 1 yr

• 16 oz = 1 lb

• 2000 lb = 1 ton

• 8 oz = 1 cup

• 2 cups = 1 pint

• 2 pints = 1 quart

• 4 quarts = 1 gallon

### Unit Analysis/Dimensional Analysis

• A method of converting from 1 set of units to another set of units using a series of conversion factors.

• A conversion factor is a fraction made from the two parts of the equivalency.

• 12 in. = 1 ft

• Each equivalency can produce two conversion factors.

### Convert 22 inches to feet

• List possible conversion factors:

• Set up grid with starting number and units in the upper left side

• Plug in conversions so that the same units are on the diagonal

### Unit Analysis Practice

• 5.75 min  months

• 135 km  cm

• 17.5 oz  gal

• 1.5 mile  inch

• 145 mg  hg

• 135 mL  L

• 5.75 min  month

• 5.75 min_ 1 hr 1 day 1 yr 12 mos= 1.31 x 104 months

• 60 min 24 hr365.25 day 1 yr

• 135 km  cm

• 135 km1000 m 1 cm = 13,500,000 cm

• 1 km 0.01 m

• 17.5 oz  gal

• 17.5 oz 1 qt 1 gal = 0.138 gal

• 32 oz4 qt

• 1.5 mile  inch

• 1.5 mile5280 ft12 in = 95,000 in

• 1 mile1 ft