DensityDensity All substances have different densities, therefore, you All substances have different densities, therefore, you

can identify a substance if you know its densitycan identify a substance if you know its density

The formula to calculate somethingThe formula to calculate something’’s density is:s density is:

When we calculate density, the units we use are either When we calculate density, the units we use are either g/mLg/mL or or g/cmg/cm33. How do we know which set of units to . How do we know which set of units to use?use?

M

D V

g/ml - g/ml - liquidsliquids volume of liquids are measured in millilitersvolume of liquids are measured in milliliters

g/cmg/cm3 3 for for solidssolids Volume of solids are measured in cmVolume of solids are measured in cm33

MassMass

To find mass, we put the object on a To find mass, we put the object on a balancebalance Mass is always in gramsMass is always in grams

How do we find volume?How do we find volume?

Volume - two optionsVolume - two options

LiquidsLiquids Use a graduated cylinder to find the volume in Use a graduated cylinder to find the volume in

mLmL SolidsSolids

If possible, measure length, width, and height; If possible, measure length, width, and height; then multiply to get your volume in cmthen multiply to get your volume in cm33

If not, use displacement of water to measure If not, use displacement of water to measure volume (you will need to convert to cmvolume (you will need to convert to cm33 when when you are done because it is a solid)you are done because it is a solid)

Measuring Solid Volume

10 cm

9 cm

8 cm

We can measure the volume of regular object using the formula length x width x height.

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We can measure the volume of irregular object using water displacement.

Amount of H2O with object = ______

About of H2O without object = ______

Difference = Volume = ______

Calculate the volume:

WaterWater

What is the density of water?What is the density of water?

Now you know how to find mass and Now you know how to find mass and volume, you can find the density of volume, you can find the density of objects.objects.

Practice 1Practice 1

V = 15 mLV = 15 mL M = 45 gM = 45 g D = ?D = ?

D = m/vD = m/v

D = 45 g/ 15mLD = 45 g/ 15mL

D = 3g/mLD = 3g/mL

Practice 2Practice 2

V = 10 mLV = 10 mL M = 100 gM = 100 g D = ?D = ?

D = m/vD = m/v

=100 g/10mL=100 g/10mL

D = 10 g/mLD = 10 g/mL

Practice 3Practice 3

V = 17 mLV = 17 mL M = 34 gM = 34 g D = ?D = ?

D = M/VD = M/V 34 g/ 17 ml34 g/ 17 ml

D = 2 g/mLD = 2 g/mL

Practice 4Practice 4

M = 45 gM = 45 g D = 9 g/cmD = 9 g/cm33

V = ?V = ?

V = m/dV = m/d 45 g/ 9 g/ cm45 g/ 9 g/ cm33 V = 5 cmV = 5 cm33

Practice 5Practice 5

M = 144 gM = 144 g D = 12 g/cmD = 12 g/cm33

V = ?V = ?

V= m/dV= m/d 144 g/12 cm144 g/12 cm33

V = 12 cmV = 12 cm33

Practice 6Practice 6

M = 27 gM = 27 g D = 108 g/cmD = 108 g/cm33

V = ?V = ?

v = m/dv = m/d 27 g/ 108 g/cm27 g/ 108 g/cm33

V = .25 cmV = .25 cm33

Practice 7Practice 7

D = 12 g/mLD = 12 g/mL V = 3 mLV = 3 mL M = ?M = ?

M = d x vM = d x v 12 g/mL x 3 mL12 g/mL x 3 mL

M = 36 gM = 36 g

Practice 8Practice 8

D = 1445 g/mLD = 1445 g/mL V = 2 mLV = 2 mL M = ?M = ?

M = d x vM = d x v 1445 g/mL x 2 mL 1445 g/mL x 2 mL M = 2890 gM = 2890 g

Practice 9Practice 9

D = 3.54 g/mLD = 3.54 g/mL V = 22 mLV = 22 mL M = ?M = ?

M = d x vM = d x v 3.54 g/mL x 22 mL 3.54 g/mL x 22 mL

M = 77.88 gM = 77.88 g