Density

=Density and Temperature =

__**Clarifying Important Terms**__
- __Density__ is the ratio of an object's mass to its volume. - __Mass__ is the measure of the amount of matter that an object contains; the SI base unit for mass is the kilogram. - __Volume__ is a measure of the space occupied by a sample of matter.

**__The Key Concept__**
- The __**volume**__ of most substances **increases** as the temperature increases. - The mass remains the same despite the volume change and the temperature. **- The density of a substance generally decreases as its temperature increases.** - **Density** changes with temperature because the volume changes with temperature. - When the temperature increases, The volume, the space occupied by the matter is getting bigger/increases, but the mass is staying the same, so it is becoming less dense. - Over a certain range of temperature, the volume of water increases as its temperature decreases. Ice, or solid water, floats because it is less dense than liquid water.

=Calculating Density =

__mass__- units g, kg, ect.. __volume__- units cm3, m3, ect... __Density__- units g/cm3, ect..

**Problem**:
A block of aluminum has a volume of 15.0 mL and a mass of 40.5 g. What is the density?

1. **Analyze**: list the known facts and the unknown.
- mass= 40.5 g - volume= 15.0 mL __**Unknown**__ - density= ?
 * __Known__**

2. **Calculate**: solve for the unknown
- substitute the known information and calculate.

D= Mass/volume = 40.5 g/ 15.0 mL = 2.70 g/mL

3. **Evaluate**: does this make sense__**?**__
= Using Density to Calculate Volume = - What is the volume of a pure silver coin that has a mass of 14 g? The density of a silver (AG) is 10.5 g/cm3.

** 1. Analyze: **List the knowns and the unknown.
__**Knowns**__ Mass of coin = 14g Density of silver= 10.5 g/cm3

__**Unkown**__ Volume of coin= ? cm3.

- Solve this problem by using density as a conversion factor. You need to convert the mass of the coin into a corresponding volume. The density gives the following relationship between volume and mass.

1 cm3 Ag= 10.5 g Ag

- Notice that the known unit is in the denominator and the unknown unit is in the numerator.

** 2. Calculate: **Solve for the unknown
- Multiply the mass of the coin by the conversion factor to yield an answer in cm3. 14 g Ag X 1 cm3 Ag/ 10.5 g Ag= 1.3 cm3 Ag.

** 3. Evaluate: **Does this make sense?
=[|Density work sheet]= = =

1. a. 1.98 g/mL b. 2 g/mL c. 1.26 g/ mL d. 7.8 X 10 ^-3 g/mL e. 7.95 g/ml 2. a. 3.54 ml b. 316.6 ml

The rest of the worksheet doesn’t pertain to the chapter, so don’t do the rest of the problems