Processing Lab DataMRS. PAGE

2014-2015

After Collecting Data = Process Data

Raw Data: the data you collect during lab without any calculations Qualitative Data: Descriptive data – observed with senses, (i.e. what does it

look like, sound like, feel like)

Quantitative Data: Measured data using tools. Will be number values.

Processed Data: data as a result of performing calculations AFTER all data has been collected

Raw Data & Processed Data are kept on SEPARATE DATA TABLES!!!

DENSITY

Density is a physical property of matter Density refers to how tightly packed the particles are in an

objectTightly packed = more denseLoosely packed = less dense

or Units for density are or (note:

Practice Calculating Density

If you measure an object that has a mass of 8.47 g and a volume of 3.1 cm3. Calculate the density of the object.

¿2 .7𝑔𝑐𝑚3

Remember Sig. Fig. Rules

YOU TRY

What is the density of an 84.70 g sample of an unknown substance if the sample occupies 49.6 mL?

What volume would be occupied by 7.75 g of the same substance? (Use the density from the first problem)

𝟏 .𝟕𝟏𝑔𝑚𝐿

𝟒 .𝟓𝟑𝒎𝑳

Accuracy vs. Precision

Accuracy: how close a measurement is to an accepted value (literature value)

Precision: how close the measurements are to each other

Percentage Error

You can determine how accurate your data is by calculating the percentage error

The larger the percentage error, the more inaccurate your data is The smaller the percentage error, the more accurate and reliable

your results are. Note: error can be positive or negative, this just means your values

are higher or lower than the accepted value

Practice Calculating Percentage Error

What is the percentage error for a mass measurement of 17.8 g, given that the correct value is 21.2 g?

% 𝐸𝑟𝑟𝑜𝑟=𝐴𝑐𝑡𝑢𝑎𝑙−𝐴𝑐𝑐𝑒𝑝𝑡𝑒𝑑

𝐴𝑐𝑐𝑒𝑝𝑡𝑒𝑑×100

% 𝐸𝑟𝑟𝑜𝑟=17.8−21.221.2

×100 ¿−3.421.2

×100 ¿−16.0%

Remember Sig. Fig. Rules

YOU TRY…

A volume is measured experimentally as 4.26 mL. What is the percentage error, given that the correct value is 4.15 mL?

A student measures the mass and volume of a substance and calculates its density as 1.40 g/mL. The correct, accepted, value of the density is 1.30 g/mL. What is the percentage error of the student’s measurement?

𝟐 .𝟕%

𝟕 .𝟕%

Experimental Errors

2 Types: Random & Systematic Random Errors: unpredictable, chance variations that experimenter

has little control over– using many trials and averaging results helps alleviate this type of error. (ex: parallax error)

Systematic Errors: caused by the way in which the experiment was conducted (design). Systematic errors can not be eliminated by averaging. Must change how experiment is conducted. (ex: not calibrating instruments)

Human Error: should not occur if you are focused and careful

HOMEWORK

Read/review pages 44-57 in your textbook.

Complete questions 1-8 on page 57. SHOW ALL WORK.