Transcript Processing Lab Data

Processing Lab Data
MRS. 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
object
 Tightly
packed = more dense
 Loosely


𝐷𝑒𝑛𝑠𝑖𝑡𝑦 =
packed = less dense
𝑚𝑎𝑠𝑠
𝑉𝑜𝑙𝑢𝑚𝑒
or 𝐷 =
Units for density are
𝑔
𝑚𝐿
𝑚
𝑉
or
𝑔
𝑐𝑚3
(note: 1𝑚𝐿 = 1𝑐𝑚3 )
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.
𝐷=
𝑚
𝑉
=
8.47𝑔
3.1𝑐𝑚3
=
8.4𝑔
3.1𝑐𝑚3
= 2.7
𝑔
𝑐𝑚3
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?
𝟏. 𝟕𝟏
𝑔
𝑚𝐿
 What
volume would be occupied by 7.75 g of the
same substance? (Use the density from the first
problem)
𝟒. 𝟓𝟑 𝒎𝑳
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

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
𝐸𝑥𝑝𝑒𝑟𝑖𝑚𝑒𝑛𝑡𝑎𝑙 𝑉𝑎𝑙𝑢𝑒 −𝐴𝑐𝑐𝑒𝑝𝑡𝑒𝑑 𝑉𝑎𝑙𝑢𝑒
𝐴𝑐𝑐𝑒𝑝𝑡𝑒𝑑 𝑉𝑎𝑙𝑢𝑒
× 100
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?
𝐴𝑐𝑡𝑢𝑎𝑙 − 𝐴𝑐𝑐𝑒𝑝𝑡𝑒𝑑
% 𝐸𝑟𝑟𝑜𝑟 =
× 100
𝐴𝑐𝑐𝑒𝑝𝑡𝑒𝑑
17.8 − 21.2
% 𝐸𝑟𝑟𝑜𝑟 =
× 100
21.2
−3.4
=
× 100
21.2
= −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?
𝟐. 𝟕%

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?
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.