Guess My Rul e
Directions: Look at the patterns below and add the numbers or shapes
that continue the same pattern. After you have continued the pattern,
write the rule that you used to complete the pattern.
1.
1
2
3
4
_____ _____ _____ _____
2
4
6
8
_____ _____ _____ _____
Rule:
2.
Rule:
3.
_____ _____ _____ _____
Rule:
4.
_____ _____ _____ _____
Rule:
5.
_____
Rule:
6.
1
Rule:
7.
Rule:
4
9
16
_____ _____ _____ _____
Density is a Periodi c Property
Discovering an Element
Introduction
Directions: Read the passage and answer the questions that follow.
Dmitri Mendeleev thought of the rules for classifying elements in 1869-1871.
Because of the rules he used to classify the elements, Mendeleev was able to
predict the physical properties of three elements that had not been discovered
yet.
When Medeleev began his famous work with the elements, 63 elements had
been discovered. The physical and chemical properties of these elements had
been studied and their atomic masses measured. Mendeleev put the elements
in a table of rows and columns that looked like a calendar. The elements were in
order of increasing atomic mass and repeating physical and chemical properties.
When Mendeleev looked at the patterns on his periodic table, he noticed that in
order to keep the pattern going, there must be missing elements. Mendeleev
was able to predict the physical properties (atomic mass, melting point, density,
and specific heat) of the elements that had not been discovered yet.
In 1886, the element germanium was discovered by a German chemist named
Clemens Winkler. Germanium was one of the elements that Mendeleev had
predicted by using his rules, 15 years earlier. Two other elements were soon
discovered that also had properties very similar to those predicted by Mendeleev.
The periodic table that you use in your science class is organized in order of
increasing atomic number (number of protons) instead of atomic mass, but is still
very similar to Mendeleev’s periodic table.
Problem
Today you will be using your knowledge of the periodic table to predict one of the
physical properties of Mendeleev’s missing element…Germanium.
1. Who was Dmitri Mendeleev?
2. How many elements had been discovered when he began his work?
3. How was Mendeleev’s periodic table organized?
4. What could Mendeleev do that was so amazing?
5. Pre-Lab Questions
Element
Aluminum
“Mystery Element”
Indium
Thallium
Period
3
4
5
6
Density (g/cm3)
2.70
7.31
11.85
1. One of the elements that Mendeleev predicted was in the fourth period
(row) of the periodic table, in Group 3. Use the graph above to predict the
density of the mystery element.
Density of mystery element = _________________________________
Hint: To get your answer draw a best-fit line, the best straight line that you can
draw that includes at least 2 points. You are not connecting all three points.
Materials
Each group will need:
Lead Shot, 35 -40g
Silicon lumps, 8-10 g
Tin shot, 25-30 g
Water
Paper towels
Marking pen or pencil
Triple-Beam Balance
3 x 50 mL beakers, or small cups
Forceps or tongs
25 mL graduated cylinder
Safety Information
Lead powder is toxic by inhalation and ingestion. Using lead shot does not
present a powder or dust hazard. Do not work with lead powder. Silicon in
powder form is slightly toxic. Do not handle fine silicon powder at the bottom of
the beaker or bottle. Wear chemical splash goggles and chemical-resistant
gloves and apron. Wash your hands with soap and water before leaving the
classroom.
Procedure
Part 1: Silicon
1.
Take one of your 50 mL beakers, and label it Silicon.
2.
Find the mass of the beaker, using the triple beam balance and record
it on the data table.
3.
Add about 8 g silicon to the beaker. Take the mass of the beaker and
the silicon. Record this on your data table.
4.
Place 10 mL of water in a 25 mL graduated cylinder. Record in the
data table.
5.
Using forceps or tongs, carefully add the silicon chunks to the
graduated cylinder. Add the solid slowly, to avoid splashing water
or avoid breaking the graduated cylinder.
6.
Measure the new volume of the water and silicon chunks. Record this
value in the data table.
7.
Empty the water from the graduated cylinder and pour the silicon
chunks onto a paper towel to dry. Do not let any of the solid go
down the drain.
8.
Rinse the graduated cylinder with water to make sure all of the solid
has been removed.
Part 2: Tin
9.
Take the second 50 mL beaker, and label it Tin.
10. Find the mass of the beaker, using the triple beam balance and record
it on the data table.
11. Add about 25 g tin to the beaker. Take the mass of the beaker and the
tin. Record this on your data table.
12. Place 10 mL of water in a 25 mL graduated cylinder. Record in the
data table.
13.
14.
15.
16.
Using forceps or tongs, carefully add the tin shot to the graduated
cylinder. Add the solid slowly, to avoid splashing water or avoid
breaking the graduated cylinder.
Measure the new volume of the water and tin. Record this value in the
data table.
Empty the water from the graduated cylinder and pour the tin shot onto
a paper towel to dry. Do not let any of the solid go down the drain.
Rinse the graduated cylinder with water to make sure all of the solid
has been removed.
Part 3: Lead
17. Take the third 50 mL beaker and label it lead.
18. Find the mass of the beaker, using the triple beam balance and record
it on the data table.
19. Add about 35 g lead to the beaker. Take the mass of the beaker and
the lead. Record this on your data table.
20. Place 10 mL of water in a 25 mL graduated cylinder. Record in the
data table.
21. Using forceps or tongs, carefully add the lead shot to the graduated
cylinder. Add the solid slowly, to avoid splashing water or avoid
breaking the graduated cylinder.
22. Measure the new volume of the water and lead shot. Record this value
in the data table.
23. Empty the water from the graduated cylinder and pour the lead shot
onto a paper towel to dry. Do not let any of the solid go down the
drain.
24. Rinse the graduated cylinder with water to make sure all of the solid
has been removed.
Period
Data Table 1
Mass
Mass
Mass Volume Volume Volume Density=
Element
of
of
of
of
of
of
mass
Beaker Beaker Sample Water
Water Sample volume
and
and
Sample
(g)
(g)
Sample
(mL)
(mL)
(g/cm3)
(g)
(mL)
Silicon
Tin
Lead
10 mL
Data Analysis
Directions: Complete the following calculations using information from
Data Table 1.
1. Calculate the mass for all three samples.
(mass of beaker and sample – mass of beaker = mass of sample)
2. Calculate the volume for all three samples.
(volume of water and sample – volume of water = volume of sample)
3. Using the mass and volume, calculate the density of each sample.
(density = mass ÷ volume or density = mass )
volume
4. Use your periodic table of elements to find the periods for Silicon, Tin, and
Lead. Record onto Data Table 1.
5. On the graph below, plot the points that show the relationship between Density
(on the y-axis) and Period Number (on the x-axis).
Title:
6. Using a ruler, draw a “best-fit” line through the data points on your graph. Use
this line to predict the density of germanium.
Density of germanium=___________________________________________
Conclusion
Directions: Pick 4 of the prompts to write about in your journal.
7. Who was Dmitri Mendeleev? Why do we study him in science class?
8. Describe how you and Mendeleev were able to make accurate predictions about
the properties of elements on the periodic table.
9. Compare and contrast Mendeleev’s periodic table with the one that we use
today.
10. Write an email to a friend that summarizes today’s lab procedure.
11. Two of your lab partners are arguing about the lab vocabulary and about how to
measure volume of a liquid using a graduated cylinder. One says to measure
from the bottom of the ponoscus, one says to measure from the top of the
meniscus. Write what you would say to your partners so they could complete
the procedure correctly.
12. How would you calculate the density of an object that had a mass of 4 g and
volume of 8 mL? Include your formula in your work.
13. Write 3 new things you learned while doing this lab exercise. Write 3 things,
related to this lab, that you still need/want to learn more about.
Density is a Periodic Property
Make notes and get some classmate names as you
Find Someone Who…
1. Knows how many elements were discovered when Dmitri Mendeleev
began his work
Answer
Name
2. Knows the formula for density
Answer
Name
3. Knows the name of the scientist who first organized the periodic table by
atomic mass
Answer
Name
4. Knows how the periodic table is organized today
Answer
Name
5. Knows the density of an object with a volume of 6 mL and a mass of 3
grams.
Answer
Name
6. Knows the name for the “dip” in the water in a glass-graduated cylinder
Answer
Name
7. Knows how Mendeleev was able to predict the properties of undiscovered
elements.
Answer
Name
8. Knows what periodic means
Answer
Name