Density Density describes how heavy an object is compared to its size. Think of two cubes that are the same size. One is made of metal and the other is made of Styrofoam. Which will be heavier? All substances have different densities, therefore, you can identify a substance if you know its density

Mass Mass is the amount of substance in an object It is constant no matter where you go, even the moon. To find mass, we put the object on a balance Mass is always in grams

Volume - two options Volume is how much space an object takes up. To find the volume of Liquids Use a graduated cylinder to find the volume It will be measured in mL To find the volume of rectangular Solids Measure length, width, and height; then multiply. It will be measured in cm3

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 an irregular object using water displacement. Amount of H2O with object = ______ About of H2O without object = ______ Difference = Volume = ______

Calculate the volume:

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

Water What is the density of water? If an object is less dense than water it will float. If an object has a greater density than water it will sink.

To Calculate Density The formula to calculate something’s density is: D = density M = mass V = volume M D V

Practice 1 V = 15 mL M = 45 g D = ? D = m/v 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 M = 45 g D = 9 g/cm3 V = ? V = m/d 45 g/ 9 g/ cm3 V = 5 cm3

Practice 4 M = 144 g D = 12 g/cm3 V = ? V= m/d 144 g/12 cm3 V = 12 cm3

Practice 5 D = 12 g/mL V = 3 mL M = ? M = d x v 12 g/mL x 3 mL M = 36 g

Practice 6 D = 3.54 g/mL V = 22 mL M = ? M = d x v 3.54 g/mL x 22 mL M = 77.88 g