Scientific Measurements

Accuracy and Sensitivity of Measuring Devices

Accuracy 

- It is the degree of closeness of the measurements to the actual or true value.
- The extent to which a given measurement agrees with the standard value for that measurement.


Sensitivity

- It measures the proportion of actual positives which are correctly identified.

- An ability to differentiate fluctuations in a given observed or tested event.

Getting the Accuracy and the Sensitivity

- After getting the Accuracy it will be easier to get the sensitivity.

Getting the Accuracy

- It  is how close the measured values are to each other.

NOTE: Accuracy depends on the instrument you are measuring with. But as a general rule: The degree of accuracy is half a unit each side of the unit of measure.

Getting the Sensitivity

- In getting the sensitivity it is the next calibration to the accuracy. But it is not represented by a line on the measuring tool.

- In other words, it is the next place value after your accuracy. Or sometimes, it depends on the picture.

Example:

The accuracy from this ruler is 

TENTHS.

The sensitivity is HUDREDTHS.

Accuracy and Precision

- Accuracy is the degree of veracity while precision is the degree of reproducibility.

Precision

- It is a system, also called reproducibility or repeatability, is the degree to which repeated measurements under unchanged conditions show the same results.

NOTE: 
- A measurement system can be accurate but not precise, precise but not accurate, neither, or both.

• Good precision simply tells how well a series of measurements cluster around the average result. The precision is good in Figure 3 and Figure 4. The precision is poor in Figure 1 and Figure 2.

• Figure 1 and Figure 3 shows good accuracy. If the average value is close to the middle, then we have good accuracy. We can have good accuracy even when the precision is poor.

Bias is a systematic (built in) error which makes all measurements wrong by a certain amount.

Examples!

How To Compute For Percentage Error
- The calculation for percentage error is used to evaluate the degree of error in calculations and data.

- The calculation for percentage error is simple and straightforward. 

FORMULA FOR PERCENTAGE ERROR:

Example on how to do Percentage Error!

A student measures the mass and volume of a piece of copper in the laboratory and uses his data to calculate the density o the metal.  According to his results, the copper has a density of 8.37 g/cm³.   Curious about the accuracy of his results, the student consults a reference table and finds that the accepted value for the density of copper is 8.92 g/cm³.   What would be the student's percent error?

Step 1 - Determine which values are known.
                       The students result, or the observed value = 8.37 g/cm³.
                       The accepted, or true value = 8.92 g/cm³.

Step 2 - Substitute the values in the percent error calculation.

Step 3 - Solve for the unknown, and round to correct significant digits.

Percentage Error = -6.17%

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Group 3

Mendoza

Trillanes

Meily

Manibog

Macomb

Scientific Measurements

Measurements:
-quantitative observations 
-include 3 pieces of information 
1.magnitude 
2.unit 
3.uncertainty 
-measurements are not numbers 
-numbers are obtained by counting or by definition; measurements are obtained by comparing an object with a standard "unit" 
-numbers are exact; measurements are inexact 
-mathematics is based on numbers; science is based on measurement.

Units of Measurements:

A unit of measurement is a definite magnitude of a physical quantity, defined and adopted by convention and/or by law, that is used as a standard for measurement of the same physical quantity. Any other value of the physical quantity can be expressed as a simple multiple of the unit of measurement.

Calibrations:

 is a comparison between measurements - one of known magnitude or correctness made or set with one device and another measurement made in as similar a way as possible with a second device.

Accuracy:

refers to how closely the measured value of a quantity corresponds to its “true” value.

Sensitivity:

- Place value that is no longer represented in the calibration

- Place value that is already approximated/estimated

- Place value after the accuracy 

Precision:

expresses the degree of reproducibility, or agreement between repeated measurements.

Identifying Place Values:

- Each measuring device is accurate only up to a certain value.

- This place value is the smallest place value represented or that can read from measuring device

- The estimated place value is the next place value after the place value to which the instrument is accurate. 

Maegan Zablan

Romina Espuerta

Pamela Lopez

Tina Silvestre

Jam Villanueva 

Quantum Numbers

QUANTUM NUMBERS 

1)The Principle Quantum Number "n" :  This quantum number was the first one discovered and it was done so by Niels Bohr in 1913. Bohr thought that each electron was in its own unique energy level, which he called a "stationary state," and that each electron would have a unique value of 'n'

               :In this idea, Bohr was wrong. It very quickly was discovered that more than one electron could have a given 'n' value. For example, it was eventually discovered that when n=3, eighteen different electrons could have that value.


               :Keep in mind that it is the set of four quantum numbers that is important. As you will see, each of the 18 electrons just mention will have its own unique set of n, l, m, and s.


               :Finally, there is a rule for what values 'n' can assume. It is:

n = 1, 2, 3, and so on.

       : n Will always be a whole number NEVER less than one.

          :One point: n does not refer to any particular location in space or any particular shape. It is one component (of four) that will uniquely identify each electron in an atom.    

2) The Azimuthal Quantum Number "l" : about 1914-1915, Arnold Sommerfeld realized that Bohr's 'n' was insufficient. In other words, more equations were needed to properly describe how electrons behaved. In fact, Sommerfeld realized that TWO more quantum numbers were needed.  

                 :The first of these is the quantum number signified by 'l.' When Sommerfeld started this work, he used n' (n prime), but he shifted it to 'l' after some years. I'm not sure why, but it seems easier to print l than n prime and what if the printer (of a textbook) accidentally dumps a few prime symbols, leaving just the letter 'n?'


                 :The rule for selecting the proper values of 'l' is as follows:

l = 0, 1, 2, . . . , n-1

                 :l will always be a whole number and will NEVER be as large as the 'n' value it is associated with.


3) Magnetic Quantum Number "ml" : 
Specifies the orientation in space of an orbital of a given energy (n) and shape (l). This number divides the subshell into individual orbitals which hold the electrons; there are 2l+1 orbitals in each subshell. Thus thes subshell has only one orbital, the p subshell has three orbitals, and so on.
 
4) Spin Quantum number "ms" : Specifies the orientation of the spin axis of an electron. An electron can spin in only one of two directions (sometimes called up and down).
         : The Pauli exclusion principle (Wolfgang Pauli, Nobel Prize 1945) states that no two electrons in the same atom can have identical values for all four of their quantum numbers. What this means is that no more than two electrons can occupy the same orbital, and that two electrons in the same orbital must have opposite spins


            : Because an electron spins, it creates a magnetic field, which can be oriented in one of two directions. For two electrons in the same orbital, the spins must be opposite to each other; the spins are said to be paired. These substances are not attracted to magnets and are said to be diamagnetic. Atoms with more electrons that spin in one direction than another contain unpaired electrons. These substances are weakly attracted to magnets and are said to be paramagnetic.

ATOMS

SUB ATOMIC PARTICLES

• Particles that are smaller than the atom.
• Small particles composing of nucleons and atoms.
• 3 main sub atomic particles that make up the atom are the Protons, Neutrons and Electrons.

Eugene Goldstein.

PROTONS

• Positively charges sub atomic particles.
• The existence of protons was first discovered by Eugene Goldstein in 1886.
• He observed a cathode ray tube and found rays traveling in the direction opposite to that of the cathode rays. He called those canal rays and concluded that they were composed of positive particles. He called those canal rays and concluded that they were composed of positive particles. 
•   Each proton has a mass about 1840 times that of an electron.

Model of the Canal Rays Goldstein observed.

ELECTRONS

•  Negatively charged subatomic particles.
• Discovered by J. J Thomson in 1897.
•   Thomson performed experiments wherein high voltage electricity was applied across electrically charged plates in a cathode ray tube containing a very small amount of gas, a ray coming from the negatively charged electrode, the cathode was observed.

Cathode Rays observed by J.J Thomson

NEUTRONS

James Chadwick

• Neutrons are sub atomic particles with no charge but with a mass nearly equal to the proton's.
• Sir James Chadwick confirmed the discovery of another atomic particle’s existence: the Neutron.

NOTE:

ü  All atoms are made up of subatomic particles protons, neutrons and electron.

ü  The electronic charge is measured in coulombs (C).

ATOMIC NUMBER (Z)

• Indicates the number of protons and defines the element.

Example: 

<--- Gold's Atomic Number is 79. It has 79 protons and electrons and is also the 79th element in the periodic table :D

ATOMIC MASS (A)

•        The average mass of an atom of an element.

 Gold's Atomic Mass is 197 :D (Remember to round off decimals)---->

A.Z.P.E.N

•          AZPEN stands for Atomic Mass(A), Atomic Number(Z), Proton(P), Electron(E), 
  Neutron (N)
  
  
  Example:
  
  

* A chart that makes us see a more organized data for each element.

IONS

•          Atoms or groups with a positive or negative charge.
•          Formed when electrons are removed or added to a neutral atom, a charged particle of the same element is formed.
•          An ion with a positive charge is called a cation.

•         An ion with a negative charge is called an anion.

ISOTOPES

• Atoms that have the same number of protons and electrons but they each have different number of neutrons.
•            Atoms that have the same number of protons but different numbers of neutron.

Example:

Isotopes of Magnesium

Lithium-6

Lithium-7

Lithium- 8

Submitted By: Group 5

Mia San Juan

Alex Vergara

Cierra Mortega

Jhoanne Sanchez

Elma Tejada