EXPERIMENT - 1

Measurements

INTRODUCTION- In all sciences, measurements are essential. The most fundamental properties that can be measured are length, mass, and time. In chemistry, temperature is also treated as a fundamental property. Other properties of matter such as volume, area, and density are ratios or products of the fundamental properties. For example;

(a)units of area are (length x width)

(b)units of volume are (length x width x height) or (length3)

(c)units of density are (mass/length3)

The metric system is used almost exclusively in all sciences. The meter, kilogram, and the second are the basic units in the Systeme International (SI), but the meter and the kilogram are generally too large for convenient use in the chemistry laboratory.

Units in metric system are related to each other as multiples of ten and associated with prefixes such as, pico (10-12), nano (10-9), micro (10-6), milli (10-3), centi (10-2), deci (10-1), kilo (103), and mega (106).

This experiment has been designed to acquaint you with several types of measurements and measuring devices.

One of the fundamental properties of any sample of matter is its density. This property is dependent on the mass and the volume of a sample of matter. The relationship between density, mass, and volume is as follows:

Density = mass/volume or D = M / V

The density of a liquid or of a solution is usually reported in units of g/ml. The density of a solid is reported in units of grams per cubic centimeter (g/cm3). Because 1 ml is equivalent to 1 cm3, these units are interchangeable. The density of water is exactly 1.00000 g/cm3 at 4 0C and is slightly less than one at room temperature (0.9970 g/cm3 at 25 0C).

For any density determination, two quantities must be determined: the mass and the volume of a given quantity of matter. The mass can easily be determined by weighing a sample of the substance on a balance.

The mass of a sample of liquid in a container can be found by taking the difference between the mass of the container plus the liquid and the mass of the empty container.

The volume of a liquid can easily be determined by means of graduated containers such as graduated cylinders, pipettes, or others for routine measurements. The volume of a solid can be determined by direct measurement if the solid has a regular geometric shape such as a cube, rectangle, or cylinder.

A convenient way to determine the volume of a solid (usually irregular-shaped) is to measure accurately the volume of liquid displaced (raised) when an amount of the solid is dropped (immersed) in the liquid. The volume of the solid will equal the volume of liquid which it displaces.

Experimental Procedure

A. Mass Measurements

After cleaning the pan and zeroing the balance, take a coin (penny) and measure its mass to +/- 0.01 g. Record the mass on the report page in g and mg. Repeat the measurement for two other coins.

B. Volume Measurements
  1. Read the volume of liquid in the graduated cylinder designated by instructor to +/- 0.1 ml
  2. Using a dropper, measure the volume of 20 drops of tap water in a 10-ml graduated cylinder.
  3. Using a 10-ml pipette, transfer 10 ml tap water to a 25-ml graduated cylinder and read the volume of tap water in the graduated cylinder.
  4. Using a ruler or meter stick, measure the length, width, and height (thickness) of a given wooden block and calculate the volume of the block.
  5. Measure the volume of a given irregular shaped solid by water displacement method.
C. Temperature Measurements

Using a thermometer, determine the temperature of the following:

I. 50 ml tap water in a 150-ml beaker

II. 50/50 mixture of tap water and ice in a 150-ml beaker

III. 50/50 mixture of tap water and hot water in a 150-ml beaker

D. Density Measurements

Solid:

Method I. Weigh a given solid on a balance to the nearest 0.01g. Make sure you zero the balance before proceeding with each measurement.

Insert the solid into a 100-ml graduated cylinder filled one-half with tap water. Note and record as precisely as the initial water level, and the water level after the solid is immersed. Read the lowest point of the meniscus in determining and estimating the water level to the nearest 0.1 ml. Discard the water and repeat this measurement twice. Calculate the average density of the solid.

Method II. Weigh a given solid on a balance to the nearest 0.01g. Make sure you zero the balance before proceeding with each measurement.

Measure the dimensions of the solid with a measuring stick ruled in centimeters. Repeat these measurements twice. Determine the volume of the solid from these dimensions. Calculate the average density of the solid.

Liquid:

Weigh a 50-ml Erlenmeyer flask. Use a 10-ml graduated cylinder and add 10 ml rubbing alcohol (isopropyl alcohol) into the flask and reweigh. Repeat these measurements twice. Calculate the average density of the alcohol.

EXPERIMENT – 1

REPORT FORMName ______

Instructor ______

Date ______

A. Mass Measurement

Mass of a penny ______g ______mg

B. Volume Measurements

I. Volume of water in graduated table ______ml

II. Volume of 20 drops water ______ml

III. Volume of water delivered by pipet in graduated cylinder ______ml

IV. Dimensions: L = ______cmW = ______cm H = ______cm

Volume = ______cm3 (show your calculation)

V. Volume of solid by water displacement method ______ml

C. Temperature Measurements

I. Temperature of tap water ______0C______0F

( show calculation for conversion of 0C to 0F)

II. Temperature of tap water + ice______0C

III. Temperature of tap water + hot water______0C

D. Density Measurements

Solid:

Method (I)

Mass of solid ______g______g

Initial volume of water (V1)______ml______ml

Final volume of water (V2)______ml______ml

Volume of solid (V2 - V1)______ml______ml

Density of solid (show your calculation) ______g/ml______g/ml

Average density______g/ml

Method (II)

Mass of solid ______g

Dimensions of solid: L = ______cm W = ______cm H = ______cm

______cm ______cm ______cm

Volume of solid (show your calculation) V = ______cm3

Density of solid (show your calculation) D = ______g/ cm3 ______g/ cm3

Average density ______g/cm3

Liquid

Mass of empty 50-ml flask______g ______g average ______g

Mass of flask + 10.0 ml alcohol______g ______g average ______g

Mass of alcohol (average) ______g

Density of alcohol (show your calculation) ______g/ cm3

EXPERIMENT – 1 Name

Pre- laboratory Questions and Exercises

Due before lab begins. Answer in space provided.

  1. Define the terms precision and accuracy in such a way as to distinguish between them.
  1. Give four intensive properties that are frequently measured in Laboratory.
  1. A 24.20 g solid metal displaces 1.26 ml of water. Calculate the density of solid metal.
  1. A perfect cube of aluminum metal was found to weigh 20.00 g. The density of aluminum is 2.70

g/ml. What are the dimensions of the cube?

  1. What is the equivalent 0C for –40 0F?

EXPERIMENT – 1 Name

Post- laboratory Questions and Exercises

Due after completing lab.Answer in space provided.

1. How do you distinguish between mass and weight of material?

2. Calculate the density of a rectangular solid, which has a mass of 25.71 g. It is 2.30 cm long,

4.01 cm wide, and 1.82 cm high.

3. What is the difference, if any, between specific gravity and density in metric units? What is the

specific gravity of alcohol having a density of 0.79 g/ml?

4. If 15 drops of ethanol from a medicine dropper weigh 0.60 grams, how many drops does it take

from a dropper to dispense 1.0 ml of ethanol? The density of ethanol is 0.80 g/ ml.

5. Using appropriate table in Handbook of chemistry and physics, report the density of each of the

following substances;

a) Mercury metalb) Wood alcohol (methanol)c) zinc chloride

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