Laboratory techniques and measurements

LABORATORY TECHNIQUES AND MEASUREMENTS

University affiliation

Abstract

This practicalwas conducted to introduce us laboratory techniques and measurements.Techniques are the methods employed in the lab to collect informationthat are used to study various concepts. The experiment begins withmeasuring the length that is then converted to other units. Thesecond part is the measurement of the temperature of ice and tapwater. The third part involved volumetric measurements where pipettewas employed to measure volume, both for liquid and solid materials.The fourth part introduces measuring mass using the electronicweighing equipment. The next part involved calculation of densityfrom volume and mass. The Archimedes principle is then employed inthe calculation of volume. Archimedes principle and waterdisplacement method are used when calculating of the density ofirregular objects. The last part of this experiment was anintroduction to dilution technique.

Experiment andobservation

The temperature,mass, length and volume of various objects were measured and recordedin the below tables. The procedures used in each case were adoptedfrom the lab instructions on “Laboratory Techniques andMeasurements”.

Table 1: length

Object

Length (cm)

Length (mm)

Nickel

2

20

AA Battery

4.8

48

Clothes Pin

7.8

78

Table 2: Temperature

Water

Temperature (0C)

Hot water from tap

51

Boiling water

95

Boiling water after 5 minutes

97

Cold water from tap

19

Ice water

9

Ice water after 5 minutes

4

Table 3: Volumetric measurement

Test tube volume

Number of drops in 1ml

Pipette volume

9 ml

27 drops/ml

4 ml

Table 4: Measurement of mass

Object

Estimated mass (g)

Actual Mass (g)

Nickel

2

4.9

AA battery

15

23.7

Clothes pin

8

5.5

Baseball

120

145

Tungsten wedding band

7.5

9.7

Steel BB

2

2.1

Army ID

3

4.1

Table 5:Measurement of density

Object

Mass of cylinder +substance (g)

Graduated cylinder

Mass of substance (g)

Volume of substance (ml)

Density

(g/ml)

Water

21.4

16.5

4.9

5

0.98

Isopropyl alcohol

21

16.5

4.5

5

0.9

Saturated salt solution

22.5

16.5

6

5

1.2

Table 6: density of irregular objects

Water displacement

Object

Cylinder volume (ml)

Cylinder volume + object (ml)

Object volume (ml)

Object mass

(g)

Density

(g/ml)

Metal bolt

12.5

13.5

1

8.0

8.0

Magnet

12.5

13.5

1

4.6

4.6

Archimedes method

Object

Displaced volume

Mass of object

density

Metal bolt

1.0 cc

8 g

8.0 g/cc or 8 g/ml

Magnet

1.0 cc

4.6 g

4.6 g/cc or 4.6 g/ml

Math calculation method

Object

Volume

Mass

Density (Mass/volume)

Magnet

1.27 cm3

4.6g

3.63 g/cm3

Dilution of solution

The volume a solution of known concentration was measured using apipette and poured in a volumetric flask. Distilled water was addedcarefully to the mark. The flask with the solution was turned upsidedown 3 times to ensure homogenous solution.

Calculation and errors

The data collected during the experiment may not be precise sincethey were collected through measurement. Inaccuracy of themeasurements may be caused by faulty measuring apparatus such as thepipette, thermometer and the weighing machine. Incorrect observationmay also have been the cause of errors in the experiment. Forexample, when reading the volume of water in the cylinder, takingreading of the volume by noting the meniscus is the appropriate.Apart from this, the reading is considered inaccurate. There werechallenges encountered during the measurement of mass of salt and themass recorded may not be the exact mass of the salt.

Discussion

The main purpose of this experiment was to act as an introduction tochemistry especially laboratory techniques and measurements. Themeasurements that were focused in this experiment include mass,temperature, length, volume, density and dilution of solution. Thesemeasurements are important in chemistry as they involved mostexperiments conducted in the chemical laboratories. The experimentenabled me to gain an understanding of the importance of accuracyduring observation and recording of the collected data. Theconclusions of various experiments greatly depend on the datacollected. Therefore, their accuracy is much importance during anyexperiment.

Questions

Q. A

Water boils at 100 0C at sea level but in this experiment the highesttemperature recorded was 97 0C. The boiling point of water decreaseswith increase in altitude and due to the fact that the experiment wasconducted at 6600 ft. above the sea level, the boiling point of waterwas lower its actual boiling point.

Q B

%error=

%error=

=2%

%error=

=-0.8%

Percentage error= 2% and -0.8%

Q C: An unknown, rectangular substance measures 3.6 cm high, 4.21 cmlong, and 1.17 cm wide. If the mass is 21.3g, what is thissubstance’s density?

Density=

Density=

=1.2 g/cm3

Q D: A sample of gold (Au) has a mass of 26.15 g. Given that thetheoretical density is 19.30 g/mL, what is the volume of the goldsample?

Volume=

=

=1.35 cm3

Q E

The method which is more accurate is the water displacement method.This is because the object only displaces its own volume whereas inthe Archimedes method, the volume used in calculation also includedthe volume of the string suspending the objects.

Q F

In Archimedes method, the focus is on the volume of water the objectdisplaces and not its volume. When the object is not suspended usingstring, the weight of the object will be measured instead of thewater.

Q G

The density obtained through Archimedes’ method was higher thanthat obtain through math calculation. The masses were the same butthe volumes differed resulting to different volumes. The mathcalculation method of density calculation seems to be more accurateas the Archimedes’ method is associated with more errors.

Q H

The density of gold is 19.3 g/cm3 but the density of gold in thiscase is 15 g/cm3. This can be as a result of impurities in the goldthat lowers its mass given that the volume is maintained.

Additional questions

Q 1

Volume of 1M HCl to be used=

=2.5 ml

Volume of distilled water to be added= 10-2.5 =7.5 ml

Moles in 25 ml drink=

= 0.06075 moles

Concentration of the drink in 250 ml volumetric flask= 1000 X0.06075/250= 0.243M HCl.

Q 2.

The color of the drink will be lighter. This is because it containsless moles/particles that make the drink.

Q 3.

The boiling point of water decreases with increase in altitude andhence the boiling point of water will be lower than the actualboiling point.

Q4

  1. Mass of mercury= =

=

Volume of mercury at 50 0C= (V1x0.9954) mm

  1. 1.36 x 1026

Q5.

  1. Mass of gold= 19.3 x volume ((22/7) x 4.12 X 21)

=21412.578 g

Mass of the can= 3 x ((22/7) X 4.12 x 21)

=3328.38 g

  1. The alarm will trip because sand and the gold do not have the same mass despite them having the same volume.

Reference

Muncaster, R. (2003).&nbspA-level physics. Cheltenham:Thornes.

Nitz, O. W., Ondrus, M. G., &amp Melton, T. (1993).&nbspLaboratorymanual for introductory chemistry. Dubuque, Iowa: Wm. C. Brown.

Bauer, R. C., Birk, J. P., &amp Sawyer, D. J. (2009).&nbspLaboratoryinquiry in chemistry. Belmont, CA: Brooks/Cole, CENGAGE Learning.