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Density

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**Comparing Feathers and Rocks**

Which do you think would have the greater mass? Which do you think would have the greater volume? 1 kg of feathers 1 kg of rock

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**Density Density is defined as mass per unit volume.**

Density is a measure of how tightly packed molecules are in an object. Basically, it is the amount of matter within a certain volume. Density is the amount of matter within a certain volume.

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**The Math… The Units: Mass = Grams (g) Volume (2 ways) Density (2 ways)**

Ruler = cm3 Displacement = ml Density (2 ways) Ruler = g/cm3 Displacement = g/ml

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**IRON! It has the most mass for that volume.**

What is Density? If you take the same volume of different substances, then they will weigh different amounts. Water Iron Wood 1 cm3 0.50 g 1.00 g 8.00 g Q) Which of these is most dense? Why? IRON! It has the most mass for that volume.

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**Density for different things…**

Substance Density (g/cm3) Hydrogen Helium Air (atmospheric air) Carbon Monoxide Carbon Dioxide Gasoline 0.70 Ice 0.922 Water 20deg C) 0.998 Water 4deg C) 1.000 Milk 1.03 Magnesium 1.07 Water in the Dead Sea (31.5% salt in the water) 1.24 Aluminum 2.7 Iron 7.8 Lead 11.3 Mercury 13.6 Gold 19.3 21.4 Each substance has it’s own density. It does not matter how much of a substance you have, it will have the same density. 1 gram of water will have the same density as 100 grams of water Distilled Water has a density of 1 g/cm3 (This is the only density you need to memorize!)

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**Density for different things…**

Substance Density (g/cm3) Hydrogen Helium Air (atmospheric air) Carbon Monoxide Carbon Dioxide Gasoline 0.70 Ice 0.922 Water 20deg C) 0.998 Water 4deg C) 1.000 Milk 1.03 Magnesium 1.07 Water in the Dead Sea (31.5% salt in the water) 1.24 Aluminum 2.7 Iron 7.8 Lead 11.3 Mercury 13.6 Gold 19.3 21.4 Objects with different densities interact in a very predictable way The more dense object will sink, the less dense will rise to the top…

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**Different objects have different densities**

Is the ice or the water more dense? The water is more dense than the ice because the ice floats! Objects with less than 1 g/cm3 density will float in tap water (ex: ice at 0.93) Objects with more than 1 g/cm3 density will sink in tap water (ex: gold at 19.3)

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Sidenote… Sulfur hexaflouride. Density? Explain this.

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**The Math… The Units: Mass = Grams (g) Volume (2 ways) Density (2 ways)**

Ruler = cm3 Displacement = ml Density (2 ways) Ruler = g/cm3 Displacement = g/ml

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**Find the mass of the object**

Determining Density Step 1: Find the mass of the object

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**Determining Density STEP 2: Determine Volume**

We have 2 ways to determine VOLUME. Measure Cube = L * W * H Cylinder = Πr2H Sphere = (4Πr3)/3 Calculate Displacement Displacement is how much liquid is moved out of the way to make room for the object placed in water

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**Determining Volume: Displacement**

Calculate Displacement Displacement is how much liquid is moved out of the way to make room for the object placed in water

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**Determining Density Step 3: Calculate Density = Mass Volume Units:**

For ruler: g/cm3 For displacement: g/ml

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To find density: Find the mass of the object Find the volume of the object Divide : Density = Mass / Volume Ex. If the mass of an object is 35 grams and it takes up 7 cm3 of space, calculate the density.

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To find density: Find the mass of the object Find the volume of the object Divide : Density = Mass / Volume Ex. If the mass of an object is 35 grams and it takes up 7 cm3 of space, calculate the density. Set up your density problems like this: Known: Mass = 35 grams Unknown: Density (g/cm3) Volume = 7 cm3 Formula: D = M / V Solution: D = 35g / 7cm3 D = 5g/cm3

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**Practice Problem 1 Osmium is a very dense metal. What is its**

density in g/cm3 if g of the metal occupies a volume of 2.22cm3? 1) g/cm3 2) 22.5 g/cm3 3) 111 g/cm3

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Practice Problem #3 What is the density (g/cm3) of 48 g of a metal if the metal raises the level of water in a graduated cylinder from 25 mL to 33 mL? A) 0.2 g/ cm B) 6 g/cm3 C) g/cm3 25 ml mL lecturePLUS Timberlake

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