No, 14-carat gold is not pure gold. While the density of pure gold is 19.3 g/cm^3, the lower density of the 14-carat gold (157 g/13.8 cm^3 = 11.4 g/cm^3) indicates it contains other metals mixed in besides gold.

1. 12/12 B Day
LEQ: How can we use density to tell if
an element is pure?
1. What is one element that has similar
properties to hydrogen?
2. Would you expect sodium (Na) to be
malleable?
3. Why or why not? (Explain your answer!)
4. Would you expect xenon (Xe) to be ductile?
5. Why or why not? (Explain your answer!)

2. Today’s LEQ: How can we use density
to tell if an element is pure?
By the end of today, you should be able to…
1. SOLVE to find the density of an object using
the density equation.
2. Use data on density to determine if an
element is pure

3. Focus Vocabulary:
77. Mass
78. Volume

4. Activating Strategy
14-carat 24-carat
Which ring would you rather have?

5. Draw this in your notes:
=

6. Draw this in your notes:
MASS = how much
matter is in an object
(how many ATOMS
are in something)
=

8. Draw this in your notes:
MASS = how much
matter is in an object
(how many ATOMS
are in something)
VOLUME = how
=
much space an object
takes up (how BIG is
the object?)

9. Volume: how much space an object
takes up

10. Draw this in your notes:
MASS = how much
matter is in an object DENSITY
(how many ATOMS (how many
are in something)
VOLUME = how
= atoms
there are
in a certain
much space an object
takes up (how BIG is
space)
the object?)

11. More Dense Less Dense

12. BrainPop: Density

14. MASS = grams (g)
VOLUME = milliliters (mL) OR
3
centimeters cubed (cm )
DENSITY = grams per milliliter
(g/mL) OR grams per centimeter
3
cubed (g/cm )

15. SOLVE: D=
M
Mass: 15 g V
Volume: 3 mL
15 g
= 5 g/mL
3 mL

16. SOLVE:
Mass: 24 g
3
Volume: 4 cm
24 g 3
3 = 6 g/cm
4 cm

17. SOLVE:
Density: 4 g/mL
Mass: 12 g WHAT NOW?!
12 g
= 4 g/mL
?

18. Density Triangle:
M
÷ ÷
D V
x

19. How to use the triangle…
1. When given mass and volume:
D 2. When given mass and density:
÷ M
V=
S D
3. When given density and volume:
x D×V=M

20. SOLVE:
4 g/mL
12 g 12 g
12 g =V
4 g/mL
4 g/mL V = 3 mL

21. SOLVE:
16 g
4 mL 16 g
16 g =S
4 mL
4 mL S = 4 g/mL

22. SOLVE:
8 g/mL
4 mL 4 mL x 8 g/mL = M
M = 32 g
4 mL 8 g/mL

23. 1. 200 g
3
4,000 cm
2. 100 g 0.8 g/mL
3. 625 mL 0.64 g/mL
4. 16,000 g 625 cm
3
3
5. 150 g 0.75 g/cm

24. LAB TIME!
Using a triple beam balance scale:
http://www.youtube.com/watch?v=jknT_OKb6yM

25. LAB TIME!
1. Write the formula for density
2. Fill in the density triangle
3. Use the scale to measure and record
the MASS of each object
4. Use your calculator to calculate the
density or the volume of each object
(don’t forget the units!)

26. EVERY ELEMENT
HAS ITS OWN
UNIQUE
DENSITY!

27. WE CAN USE
DENSITY TO
IDENTIFY
ELEMENTS!

28. HOT Q:
Unknown substance:
Mass: 12.96
Volume: 4.8
2.7
Density:________
What is the unknown
substance?!
ALUMINUM!

29. Summarizer:
3
Density of pure gold: 19.3 g/cm
Density of a 14-carat gold ring:
Mass: 157 g
3
Volume: 13.8 cm
Is 14-carat gold pure gold?
Why or why not?!