LABORATORY ACTIVITIES FOR REGENTS CHEMISTRY. Many laboratory activities require measurements....

LABORATORY ACTIVITIES FOR REGENTS CHEMISTRY

Many laboratory activities require measurements.

Science uses the S.I. (Metric System) of measurements.

Types of measurements:

–Linear (length or distance)

–Mass (weight)

–Volume

–Temperature

All measuring instruments have calibrations. These are the markings or divisions on the measuring tool.

Linear measurements are made using a Meter Stick or Metric Ruler.

Metric Ruler

Meter Stick

The basic unit for linear measurement is the meter (m.). Other commonly used units are the centimeter (cm.) and millimeter (mm.).One advantage of the metric system is that everything is based on the number, 10, or some multiple of 10.

10 mm. = 1 cm. (and 1 mm. = 0.1 cm.)

100 cm. = 1 m. (and 1 cm. = 0.01 m.)

Also, 1000 m. = 1 kilogram (kg.).

A metric ruler

cm. marks mm. marks

When making measurements, scientists use a concept and a practice known as significant

figures (Sig. Figs.)

Significant figures include an estimated digit that is always one place beyond the calibrations on any measuring instrument.

Estimating the last digit in a measurement

You might estimate the end of the cylinder to be half-way between the lines or 0.05 cm. This digit must be included in the measurement.

Estimating the last digit in a measurement

This measurement should be read as 4.95 cm. This measurement has 3 significant figures.

Reading a metric ruler correctly:

This point can be read as 1.65 cm. or 16.5 mm.

Reading a metric ruler correctly:

This point can be read as 6.70 cm. or 67.0 mm.

Mass measurements are made using a balance.

There are several kinds of balances:

• Triple beam balance

• Dial-a-gram balance

• Electronic/ digital balance

• Analytical balance

The triple beam balance:

The dial-a-gram balance:

The electronic/ digital balance:

When using this balance, it is not necessary to estimate any places.

The analytical balance:

This is used for very technical, precise applications.

Mass, in the metric system, is measured in grams (g.), centigrams (cg.) or milligrams

(mg.).

10 mg. = 1 cg. (and 1 mg. = 0.1 cg.)

100 cg. = 1 g. (and 1 cg. = 0.01 g.)

Also, 1000 g. = 1 kilogram (kg.)

As with all measuring instruments, Sig. Fig. Rules must be followed when reading a balance.

How would you read this measurement?How would you read this measurement?

This should be read as 105.00 grams (g.)This should be read as 105.00 grams (g.)

How would you read this measurement?

CHEMISTRY PART DEUX

COMMON PROCEDURES

Techniques used

for various

Activities

FILTRATIONPurpose and Definitions

•Used to separate suspensions.

•Filtrate is the liquid portion which passes through the filter paper.

•Residue (precipitate) is the portion which remains in the paper.

1. Fold a circular piece of filter paper into quarters to form a cone.

2. Insert into a funnel and dampen

Diluting Acids

ALWAYS DILUTE

BY ADDING

ACID TO WATER

Do what ya oughta add the acid to the water.

Constructing Data Tables

1. Identify the variables in the experiment.

2. Set up tables using appropriate labels and state units of measurements.

Sample Data Table for Melting Pt. Lab.Time in sec. Temp.O C

0 0

5 1

10 4

15 9

20 15

25 15

30 15

35 15

40 18

45 24

Graphing

Label the X and Y axis

The X axis is the independent variable

(consistent variable such as time)

The Y axis is the changing variable

Tem

p. C

Time in Sec. 0 5 10 15 20 25 30 35 40 45

0

4

8

12

16

20

24

Tem

p. C

Time in Sec. 0 5 10 15 20 25 30 35 40 45

0

4

8

12

16

20

24

Tem

p. C

Time in Sec. 0 5 10 15 20 25 30 35 40 45

0

4

8

12

16

20

24

Tem

p. C

Time in Sec. 0 5 10 15 20 25 30 35 40 45

0

4

8

12

16

20

24

The melting point of this substance is 15 0C as indicated by the plateau.

Final Review of Specific Labs

• Heating / Cooling Curve

• Density of solids and liquids

• Solubility Curves• % Composition

Tem

p. C

Time in Sec. 0 5 10 15 20 25 30 35 40 45 50 55 60

0

4

8

12

16

20

24

28

32

HEATING / COOLING CURVE

Solid

Liquid

Gas

Plateaus indicate change of phase. Two

phases co-exist

Solid-liquid

Liquid-gas

KNO3 saturated 110g @ 600C

Unsaturated 135g @ 800C

Super Saturated

85 g @ 400C

FINIS