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8 Note Boxes Needed. Density. Bit of Review. Box #1. Mass: the amount of matter in an object (how heavy) Volume: the amount of space an object takes up. Once you have balanced the scale, you add up the amounts on each beam to find the total mass.
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8 Note Boxes Needed Density
Bit of Review Box #1 • Mass: the amount of matter in an object (how heavy) • Volume: the amount of space an object takes up
Once you have balanced the scale, you add up the amounts on each beam to find the total mass. What would be the mass of the object measured in the picture? _______ + ______ + _______ = ________ g Measuring Mass We will be using triple-beam balances to find the mass of various objects. The objects are placed on the scale and then you move the weights on the beams until you get the lines on the right-side of the scale to match up.
Calculate the volume of this prism. 6 cm 8 cm 5 cm
The volume is 240 cubic cm.6 x 5 x 8 6 cm 8 cm 5 cm
The volume is 125 cubic cm or 125 cm35 x 5 x 5 5 cm 5 cm 5 cm
Density Box #2 • Density is the measure of the “compactness” of a material • The proximity of like atoms or molecules • More than just the “heaviness” of a substance, density includes how much space an object takes up!!
States of Matter Density • All substances have density including liquids, solids, and gases • Which state of matter is the most dense?
So why do floaties need air? • The proximity of molecules is spread out-lots of air= overall less density!
Density Box #3 • Density compares the mass of an object to its volume • The density of water is 1 g/mL • So…object’s density>1 then it will sink • If <1 then will float
Density Box #4 D = mass = g or g volume mL cm3 Note: 1 mL = 1 cm3
Learning Check 1 Osmium is a very dense metal. What is its density in g/cm3 if 50.00 g of the metal occupies a volume of 2.22cm3?
Learning Check 2 Find the density of 500 grams of a substance if its volume is 125 cm3?
Learning Check 3 • The density of glass is 2.50 g/cm3 and it displaced 3 mL of water. What was the mass of the glass?
Learning Check 4 The density of octane, a component of gasoline, is 0.702 g/mL. What is the mass of 875 mL of octane?
Box #5 So what sinks, and what floats? • Dense objects sink Dense=Down • Buoyant objects float
So why is it that… but…
So what about that soda? • If both coke and diet coke have a volume of 255 mL, why does the diet one float and the regular soda sink?
Learning Check… but… Salt Water Fresh Water
Archimedes • Archimedes Principle: An object displaces an amount of water equal to its mass
Remember • Noah’s ARKfloated because of ARCHimedes’ Prinicple
Volume Displacement A solid displaces water and that amount of displacement is equal to its volume (space taken up)! 33 mL 25 mL Box #6
Learning Check 5 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? 33 mL 25 mL
Learning Check 6 You have 3 metal samples. Which one will displace the greatest volume of water? 25 g Al 2.70 g/mL 45 g of gold 19.3 g/mL 75 g of Lead 11.3 g/mL
Buoyancy Box #7 • A buoy floats on water to show boaters where to avoid underwater objects. • A buoy floats because of buoyancy. • Buoyancy: the upward force of water on an object • A boat floats because the water pushes UP on it!
Learning Check Which diagram represents the liquid layers in the cylinder? (K) Karo syrup (1.4 g/mL), (V) vegetable oil (0.91 g/mL,) (W) water (1.0 g/mL) 1) 2) 3) K W V V K W W V K
Solution • (K) Karo syrup (1.4 g/mL), (V) vegetable oil (0.91 g/mL,) (W) water (1.0 g/mL) • Anything with a density greater than 1 g/mL will sink! Less than 1 g/mL will float! V W K
Box #8 So what happens if… • What happens to the density of an object if you cut it half? • The density remains the Same!
