Density & Graphing

Density

- The density of an object is it's mass divided by it's volume.

formula:

d=m/v

And is usually expressed in kg/L, kg/m cubed, or g/m cubed

Example

- Determine the density of a statue that has a mass of 135kg and a  volume of 65L

d= m/v

d= 135 kg/ 65L = 2.1 kg/L

Graphing


- All graphs must contain 5 important things:

1. Labelled axes
2. Appropriate scale
3. Title
4. Data points
5. Line of best fit

- There are 3 important things you can do with a graph:

1. Read the graph
2. Find the slope
3. Calculate the area

Archimedes Density and Dispalcement theory

 density measurement  device

 

Legend says that Archimedes discovered the principle of displacement while stepping into a full bath. He realized that the water that ran over equaled in volume the submerged part of his body. Through further experiments, he deduced the above mentioned Archimedes' principle. 

description source : http://www.juliantrubin.com/bigten/archimedesprinciple.html

Jomar Delos Santos

Block E

Dimensional Analysis

- Just like converting between currencies in Chemistry it is usually necessary to convert between units.
- This process is called Dimensional Analysis

Steps

1. Find a unit equality

2. Find the conversion factors

3. Apply conversion factor

4. Cancel units

Example

- How many miles are equal to 120 km?

1 mile = 1.6 km                               Unit equality

1 = 1 mile                                       Conversion factor

      1.6 km

(120 km)(1 mile)                            Use the conversion factor

               1.6 km 

= 75                                               Cancel units

Heres a short and simple way to explain if your on the right track: da_flow_chart.gif

Scientific Notation and S.D

Significant Digits

-non zero digits are always significant
-if the zero is a place keeper it is generally not significant
-any numbers to the right of a decimal point are significant if they come after a non zero number
-When adding or subtracting round to the least precise number
     -Example 7.4212-3.54=3.8812 --->3.88
                     12.3+10.771=23.071--->23.1
-When you multiply or divide round to the number with the fewest S.D's
     -Example 2.5x5.55=13.875--->14
-Constants on the data sheet have infinite S.D's

Scientific Notation
-used if we need to write a number like 1000 with only 2 S.D's
-used if we want to write the number thirty three billion four hundred million without taking up an entire line
-shows really big or really small numbers easily

Here is a video on Scientific notation and S.D http://www.youtube.com/watch?v=IIQPHC5gZT8

-Kerr Pili

SI System and Percent Error Summary

SI Prefixes


The SI system uses many prefixes to show very large or very very small amounts of numbers.

Eg.

Tera (T) 10^12
Giga (G) 10^9
Mega (M) 10^6
Kilo (K) 10^3
Hecto (h) 10^2
Deca (da) 10^1
Fundamental Units
Deci (d) 10^-1
Centi (c) 10^-2
Milli (m) 10^-3
Micro (u) 10^-6
Nano (n) 10^-9
Pico (p) 10^-12
Femto (fm) 10^-15

Here's a link where you can learn more about the SI System

http://www.youtube.com/watch?v=ruBZ_yj1mEY

Experimental Accuracy


The maximum accuracy of any measurement  is one half of the smallest division of the measuring instrument.

Eg. Ruler with the lowest of measurements is millimeters. It has a maximum accuracy of +/- 0.5mm

Eg2. The odometer in a car has a maximum accuracy of +/- 50m

Eg3. Graduated cylinder has units of 1.0mL so the accuracy of  a cylinder is around +/-0.5mL

Expressing Error

Finding error is part of science!

There are usually 3 reasons why there is error.

1. Physical errors in the measuring device
2. 'Sloppy' measuring
3. Changing ambient conditions

Calculated Errors


There are two possibilities of calculated errors.

1. Absolute Error
2. Percentage Error

Absolute Error = Measured - Accepted

Positive numbers means you're over the accepted value and negative numbers means you're under the accepted value.

Percent Error


Percent error is the most common out of all the errors.

Percent error can be calculated by

% Error = [Measured - Accepted/Accepted] x 100
(The symbols '[ ]' represent the it's absolute value)

Eg.

[17.5N - 15N/17.5N] x100
= 14%

For more information about Percent Error can be found on this link below :

http://www.youtube.com/watch?v=jm7qUpPyY7w

-Meldrick Mendoza productions. : )

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