Writing a Lab Report

Introduction• Background Information

– What you already know, research, related information, etc.

• Observations– Feel, Touch, Appearance, etc.– Be Consistent

• Problem– Experimental question.

• Hypothesis– Possible explanation for a set of observations.– Your statement must relate to the problem and why you feel

that way (Experience, Background Information, and Observations.

Procedure

• Materials– Equipment and anything else used to carry

out the present experiment.– Do not write “Pen” or “Paper”

• Methods– Experimental design, exact procedure

followed.– Someone else should be able to do precisely

what you did.

Results and Discussion

• Data Collected– Graphs, Data Table and Text reporting findings.– You need to have a TABLE, a GRAPH, and

PARAGRAPHS reporting your data.

• Discussion and explanation of findings.– Interpret data and explain HOW and WHY your

data was as it is.– Explain Everything!

Conclusions• Brief Summary of Important Data.• Was your hypothesis proved? Why?

– Support your answer

• Causes of possible error or uncertainty regarding any portion of the experiment.– If there is none, say that.

• Your expert opinion of Why and How the results were as you found them to be.– Take some guesses, Go out on a limb.

• Recommendations for future researchers and other related studies that should be done.– What else needs to be studied to gain a better

understanding of the current material?

Paper Towel Absorbency Test

Towel Area (sq cm)

Amount of Water Absorbed

trial 1 (ml) trial 2 (ml)

Fold 15 x 15 cm 225 32 33

20 x 20 cm 400 42 43

Bounty 15 x 15 cm 225 52 53

20 x 20 cm 400 62 63

Standard 15 x 15 cm 225 12 13

20 x 20 cm 400 22 23

Paper Towel Absorbency TestCreate a Title For this Graph

0

10

20

30

40

50

60

70

0 50 100 150 200 250 300 350 400 450

Label Your Independent Variable

Lab

el Y

ou

r D

epen

den

t V

aria

ble

Fold 15 x 15 cm Fold 20 x 20 cm Bounty 15 x 15 cm Bounty 20 x 20 cm Standard 15 x 15 cm Standard 20 x 20 cm

Scientific Notation

Scientific Notation

• 299,800,000 m/sec is the speed of light in a vacuum

• 602,000,000,000,000,000,000,000 is the number of atoms in 1 mol Carbon

• 0.000000000000000000000001674 g is the mass of one hydrogen atom

Scientific Notation

it is extremely cumbersome to do calculations with very large and small numbers so…

c x 10n

where c is the coefficient and n is the exponent

Scientific Notation

• 2.998 x 108 m/sec (the speed of light in a vacuum)   

         

• 6.02 x 1023 atoms (the number of atoms in 1 mol of carbon)

• 1.674 x 10-24 g (the mass of one hydrogen atom)

Scientific Notation

1. Move the decimal point so that there is only one digit to the left of the decimal.

2. Count the number of places the decimal moves.

3. If the decimal moves to the left, the exponent on 10 is equal to the number of places the decimal was moved and has a positive sign.

4. If the decimal moves to the right, the exponent on 10 is equal to the number of places the decimal was moved and  has a negative sign.

Practice Problems

7,910,000

.00000000345

1,200,000,000.0

.000098

Practice Problems

0.00416 x 106

24.8 x 10-3

0.716 x 10-4

3410 x 102

Significant Figures

Sig Figs

Significant Figures

Used to convey the confidence we have in the accuracy of our measuring methods

and measurements

8 ± 1 mL (beaker)

8.0 ± 0.1 mL (graduated cylinder)

8.00 ± 0.01 mL (buret)

How many sig figs are in the following???

23.4g 555001.0100 atoms

200mL 74.221g

3.100mm 0.001201kg

Significant Figures

Rules for Sig Fig

Rule 1

Zeros between other nonzero digits are significant.

Examples

a. 50.3 m has three significant figuresb. 3.0025 s has five significant figures

Rules for Sig Fig

Rule 2

Zeros in front of nonzero digits are not significant.

Examples

a. 0.892 has three significant figuresb. 0.0008 s has one significant figure

Rules for Sig Fig

Rule 3

Zeros that are at the end of a number and also to the right of a decimal point are significant.

Examples

a. 57.00 g has four significant figuresb. 2.000 000 kg has seven significant figure

Rules for Sig Fig

Rule 4

Zeros that are at the end of a number but left of the decimal point are not significant.

Examples

a. 100 m has ONE significant figureb. 20 m has ONE significant figure

Rules for Sig. Fig.

Extra Rule

Zeros that are at the end of a number but left of the decimal point that are measured to be significant are indeed significant.

Examples

a. A scale measures 1200. kg has four significant figures and is written in scientific notation:

1.200 x 10 kg so Rule 3 applies3

Rules for Sig Fig

Put the following into scientific notation…

23.4g 555001.0100 atoms

200mL 74.221g

3.100mm 0.001201kg

Significant Figures

Significant Figures

Round the following to the indicated number of significant figures.

23.4 g (2 sig figs)

555001.0100 atoms (3 sig figs)

2001.0345mL (5 sig figs)

74.221g (3 sig figs)

3.100mm (3 sig figs)

0.001201kg (3 sig figs)

Rules for Calculating with Significant Figures