density a physical property of matter property = a characteristic that gives a substance identity...
TRANSCRIPT
Density
a physical property of matter
Property = a characteristic that gives a substance identity
Properties of Vinegar:
- clear liquid
- strong odor
- reacts with baking soda
- acidic
Physical Properties
can be observed without changing the composition of the substance
Examples;
-Color
-Texture
-Shape
-Hardness
-Buoyancy
-Viscosity
-Miscibility
-Density
DENSITYDENSITYStyrofoamStyrofoam BrickBrick
Brick is more dense than Styrofoam because there is
more mass
packed into the
same volume
(more molecules or atoms in the same space.)
Density
Density can be defined as “unit mass per unit volume”
Density = Mass / Volume
D = m / v
Example: DensityDensity is a property of matter. If you measure the mass and the volume of an object, you can calculate it’s density using the formula:
(g) (mL)
D = m/v
Density = mass/volumeSo, the units of density must be…. g/mL
The Units for density come from this formula…
• Why is density measured in g/mL?
Because the formula for density is
(aka “grams per milliliter”) (not “gee slash em-ell”)
m mass (in grams) g
D = ----- = ------------ -------------- ----
v volume (in milliliters) mL
Measurement
Metric System
s second Time
K or o C Kelvin or
degree celsiusTemperature
Lliter Volume
g gram Mass
m meterLength
Unit Symbol UnitQuantity
Volume is special
because:
• Volume can be measured in
liters (L),
milliliters (mL), etc. s
or…
OR…
• Volume can be measured in
cubic meters (m3)
centimeters (cm3),
…..etc.
Remember;
1 cm1 cm3 3 = 1 mL = 1 mL
Remember this geometry?• Volume of a cube is ….
l x w x hi.e. 4cm x 5cm x 2cm = 40 cm3
i.e. x (5cm)2 x 10cm = 250 cm3
•Volume of a cylinder is ….
r2 h
Determining the Volume of an Irregularly Shaped Solid
22 mL 32 mL
Units of Density:– Mass is measured in g.– Volume is measured in mL or cm3.– Density is mass / volume,
(g) / (mL) (g) / (cm3) ,so..
density is measured in:
g/mLor
g/cm3
1 cm1 cm3 3 = 1 mL = 1 mL
DENSITY - an important and useful physical property
Density mass (g)volume (cm3)
Density mass (g)volume (cm3)
13.6 g/cm13.6 g/cm33 21.5 g/cm21.5 g/cm33
Aluminum
2.7 g/cm2.7 g/cm33
PlatinumMercury
Density of Gold:
19.30 g/mL
Silver:
10.50 g/mL
Aluminum: 2.70 g/mL
Atoms of some elements are more dense Atoms of some elements are more dense than others. than others.
Substance Density (g/mL)
• Air 0.0013 g/mL
• Wood (Oak) 0.80 g/mL
• Steel 7.80 g/mL
•Water 1.00 g/mL
Sample Problem
• What is the density of 5.0 g of tin that has a volume of 1.2 mL?
D = m / v
= 4.2 g/mL
D = ?
m = 5.0 g
v = 1.2 mL
Steps for Solving Problems
1. Write the shopping list:
• the unknown variable. (what’s the question asking for?)
• all of the known variables.
2. Write the formula you will be using.
3. Calculate the final answer and include the units.
Sample Problem
• What is the density of 45.0 g of a liquid that has a volume of 62.5 mL?
D = m / v
= g/mL
D = ?
m = 45.0 g
v = 62.5 mL
Variations of the Density Formula:
D = m/v
v = m/D
m = v • D
D v
m
Sample Problem
What is the volume of 21.0 g of tin? (Density of Tin = 4.2 g/mL)
v = ?
D = 4.2 g/mL
m = 21.0 g
v = m / D
v = 5 mL
Sample Problem
What is the mass of 20 cm3 of tin? (Density of Tin = 4.2 g/mL)
m = ?
D = 4.2 g/mL
v = 20 cm3
m = v D
m = 84 g = 4.2 g/cm3
= 20 mL
Review:
3 methods of measuring volume:
• directly using glassware
• geometry (e.g. l • w • h )• water displacement (vf – vi)
Variations of the Density Formula:
D = m/v
v = m/D
m = v • D
1. Write the unknown variable.
2. Write all the known variables.
3. Convert all variables to similar units.
4. Write formula you will be using.
5. Calculate: “Plug and Chug”
6. Circle your final answer with correct units.