 # Density. Which do you think would have the greater mass? Greater volume? Why?  1 kg of feathers  1 kg of rock  Same mass!  Larger volume  Same mass!

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Density

Which do you think would have the greater mass? Greater volume? Why?  1 kg of feathers  1 kg of rock  Same mass!  Larger volume  Same mass!  Smaller volume

Volume vs. Mass Volume is the amount of space something takes up Mass is the amount of matter in an object (how “heavy” something is)

Finding Mass Place the object on a scale or balance Units should be grams (g) or kilograms (kg)

Finding Volume of a Regular Shape An object with a “regular” shape is measurable and symmetric 1.Measure length (L), width (W) and height (H) 2.Multiply L x W x H 3.Make sure units make sense (cm 3, m 3 ) 4 cm x 6 cm x 5 cm = 120 cm 3 Conversion Factor: 1 cm 3 = 1mL

Finding Volume of an Irregular Shape An object that can not easily be measured 1.Use displacement  Fill a graduated cylinder or overflow can with water  Measure how much water goes up/spills out when object is placed in water Remember: 1 cm 3 = 1mL

Density is defined as mass per unit volume. It is a measure of how tightly packed and how heavy the molecules are in an object. Density is the amount of matter within a certain volume (how much “stuff” is crammed into something) Units of Density: g/cm 3 or g/mL Depends on the units used for mass and volume

Density of Phases of Matter Which phase of matter is the densest? Which phase of matter is the least dense? *Usually the solid phase of a substance will sink in it’s liquid phase because it is more dense Water is an exception! Because water expands when it freezes, solid water (ice) is actually less dense than liquid water SOLID GAS

Solids Bone2 Brick1.8 Cork0.2 Ice0.92 Marble2.7 Paraffin0.9 Rubber1.2 Bamboo0.3 Oak Wood0.7 Pine Wood0.6 Densities of Common Substances (g/mL) Metals Aluminum2.7 Copper8.9 Gold19.3 Iron7.8 Lead11.3 Silver10.5 Liquids Pure Water1.0 Sea Water1.03 Alcohol0.8 Gylcerine1.3 Milk1.03 Turpentine0.9 Mercury13.6 Gasoline0.7 Note: The density of a substance will always be the same, regardless of it’s shape or size i.e. the density of pure water is always 1 g/mL

Finding Density Formula: M = mass V= volume D = density D = M / V M = D x V V = M / D Density (D) is mass (m) per unit volume (v) per = divided by D = m/v (m ÷ v) Divided by Multiplied by

Practice Problem #1 If the mass of an object is 35 grams and it takes up 7 cm 3 of space, calculate the density. Given: Mass = 35 grams Volume = 7 cm 3 Density = ? (g/ cm 3 ) Formula: D = M / V Solution: D = 35 g / 7 cm 3 D = 5 g/cm 3

Practice Problem #2 A rectangular block of copper metal has a mass of 1896 g. The dimensions of the block are 8.4 cm by 5.5 cm by 4.6 cm. From this data, what is the density of copper? Given: M = 1896 grams V = 8.4 cm x 5.5 cm x 4.6 cm = 212.52 cm 3 D = ? (g/ cm 3 ) Formula: D = M / V Solution: D = 1896 g / 212.52 cm 3 D = 8.92 g/cm 3

Practice Problem #3 Find the mass of 250.0 mL of benzene. The density of benzene is 0.8765 g/mL. Given: V = 250.0 mL D = 0.8765 g/mL M = ? g Formula: M = D x V Solution: M = 0.8765 g/ mL x 250.0 mL M = 219.13 g

Practice Problem #4 What volume of silver metal will has a mass of exactly 2500.0 g. The density of silver is 10.5 g/cm 3. Given: M = 2500.0 g D = 10.5 g/cm 3 V = ? cm 3 Formula: V = M / D Solution: V = 2500.0 g / 10.5 g/cm 3 V = 238.10 cm 3

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