Density, Mass, Volume

Mass  The amount of matter in a substance.  Solids, liquids and gases have a mass.  Measured with a balance  Triple Beam  Electronic  Units: Grams, Kilograms

Volume  The quantity (amount) of space an object takes up.  Solids and liquids have a definite volume…gases do not.  Graduated cylinder is used for measurement of the following:  volume of liquids  irregularly shaped objects (displacement)  Difference in water level in a graduated cylinder after the object is added to an existing amount of water.  Units = mL

Volume by Displacement

Volume Continued  Volume of symmetrical objects can be measured using a ruler and equation.  Units = cm 3  Rectangle – LxWxH  Cube – L 3  Cylinder – πr 2 h

Density  The mass per unit volume of a substance.  In other words – how much matter is packed into a space.  Every kind of matter has a density which can be measured  Density is a constant property for “pure substances.”  If an object is cut in half – its density would be the same as the whole.

Density Does Not Change  Density of Gold Bar = 19.3 g/cm 3  Density of ½ Gold Bar = 19.3 g/cm 3  Density of Aluminum = 2.7 g/cm 3  Density of Aluminum Can = 2.7 g/cm 3  Density of Pyrite = 4.9 g/cm 3

Balloons and Bowling Balls…  Objects of the same volume (space an object takes up) can have very different densities…  A balloon and bowling ball of the same volume have much different masses therefore much different densities.

Density is how much “stuff” is packed into a given space. Which is more dense in each group of two? A B A A B B Hint B is 2x the size of A

Density Affects Floating & Sinking  A granite rock is more dense than water, so it sinks, while certain pieces of wood may be less dense than water so they float.  Heat rises while cold sinks. Why?

The Density of Water  Water is very unique because-  Water is more dense in its liquid form than its solid form… this is why ice floats.

Hydrometer  Instrument used to measure the relative density of liquids.  Water has a density of 1 g/mL or 1 g/cm 3  Objects with a density greater than water (>1 g/mL) sink  Objects with a density less than water (<1g/ml) float

Which liquid is denser? AB

More Liquid Densities Rubbing Alcohol.79 Lamp Oil.80 Baby Oil.83 Vegetable Oil.92 Ice Cube.92 Water1.00 Milk1.03 Dawn Dish Soap1.06 Light Corn Syrup1.33 Maple Syrup1.37 Honey1.42

Convection  The transfer of heat within liquids & gases  Heat moves atoms apart creating a lower density – why heat rises & cold sinks.  eattransfer/ eattransfer/ eattransfer/  We will revisit convection later when we discuss why volcanoes erupt, why oceans have currents, and why we have weather.

Calculating Density, Mass or Volume D M V D = m / v V = m / d M = dv  To find the density of an object you need to first measure the mass and volume.  To find the mass of an object you need to first measure the volume and know the density.  To find the volume of an object you need to first measure the mass and know the density. Units D = g/mL or g/cm 3 V = mL or cm 3 M = g

You have a mineral that has a mass of 32 g and a volume of 4 mL. What is the density?  Mass = 32 g  Volume = 4 mL  Density = 32 g / 4 mL  Density = 8 g/mL Equations D = m / v V = m / d M = dv Units D = g/mL or g/cm 3 V = mL or cm 3 M = g Asking ForEquationInfoDo the MathAnswer (with Units) ___ = _______

You have a mineral that has a density of 10 g/cm 3 and a mass of 62 g. What is the volume?  Mass = 62 g  Density = 10 g/cm 3  Volume = 62 g / 10 g/cm 3  Volume = 6.2 cm 3 Equations D = m / v V = m / d M = dv Units D = g/mL or g/cm3 V = mL or cm3 M = g Asking ForEquationInfoDo the MathAnswer (with Units) ___ = _______

You have a mineral that has a density of 7 g/cm 3 and a volume of 6 cm 3. What is the mass?  Density = 7 g/cm 3  Volume = 6 cm 3  Mass = 7 g/cm 3 x 6 cm 3  Mass = 42 g Equations D = m / v V = m / d M = dv Units D = g/mL or g/cm3 V = mL or cm3 M = g Asking ForEquationInfoDo the MathAnswer (with Units) ___ = _______

You have an object that has a mass of 21 g. You cannot measure the volume by doing L x W x H. You have use a graduated cylinder. There is 25 mL of water in the cylinder prior to sliding the object in. After you have slid the object in the cylinder shows 28 mL. What is the density?  Mass = 21 g  Volume = displacement -> 28 – 25 = 3 mL  Density = 21 g / 3 mL  Density = 7 g/mL Equations D = m / v V = m / d M = dv Units D = g/mL or g/cm 3 V = mL or cm 3 M = g Asking ForEquationInfoDo the MathAnswer (with Units) ___ = _______