Density All substances have different densities, therefore, you can identify a substance if you know its density The formula to calculate something’s density is: When we calculate density, the units we use are either g/mL or g/cm3. How do we know which set of units to use? M D V

g/ml - liquids g/cm3 for solids volume of liquids are measured in milliliters g/cm3 for solids Volume of solids are measured in cm3

Mass To find mass, we put the object on a balance Mass is always in grams How do we find volume?

Volume - two options Liquids Solids Use a graduated cylinder to find the volume in mL Solids If possible, measure length, width, and height; then multiply to get your volume in cm3 If not, use displacement of water to measure volume (you will need to convert to cm3 when 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. _____ X _____ X _____ = _____ http://resources.edb.gov.hk/~s1sci/R_S1Science/sp/en/syllabus/unit14/new/testingmain1.htm 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:

Water What is the density of water? Now you know how to find mass and volume, you can find the density of objects.

Practice 1 V = 15 mL M = 45 g D = ? D = m/v D = 45 g/ 15mL D = 3g/mL

Practice 2 V = 10 mL M = 100 g D = ? D = m/v =100 g/10mL D = 10 g/mL

Practice 3 V = 17 mL M = 34 g D = ? D = M/V 34 g/ 17 ml D = 2 g/mL

Practice 4 M = 45 g D = 9 g/cm3 V = ? V = m/d 45 g/ 9 g/ cm3 V = 5 cm3

Practice 5 M = 144 g D = 12 g/cm3 V = ? V= m/d 144 g/12 cm3 V = 12 cm3

Practice 6 M = 27 g D = 108 g/cm3 V = ? v = m/d 27 g/ 108 g/cm3 V = .25 cm3

Practice 7 D = 12 g/mL V = 3 mL M = ? M = d x v 12 g/mL x 3 mL M = 36 g

Practice 8 D = 1445 g/mL V = 2 mL M = ? M = d x v 1445 g/mL x 2 mL M = 2890 g

Practice 9 D = 3.54 g/mL V = 22 mL M = ? M = d x v 3.54 g/mL x 22 mL M = 77.88 g