# What weighs more, a pound of bricks

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What weighs more, a pound of bricks
DENSITY Here's an old joke: What weighs more, a pound of bricks or a pound of feathers? The answer is they both weigh the same. Which  takes up more space though? Obviously, the pound of feathers takes up way  more space (has a greater volume). This leads to a  very useful property of matter called DENSITY.

The bottom line is that density is not constant.
DENSITY FACTS Most kinds of matter expand when  their temperatures rise and contract  when their temperatures drop. Thus, density changes with temperature. Very cold water is  denser than hot water because the  water molecules are closer together. So as temperature increases, density decreases. The bottom line is that density is not constant. At 4°C pure water has a density of about 1 g/cu.cm, 1 g/ml. What is the density of ice?

Demonstrations:  Water and ice: What can you infer  about the density of these items?

Gases are always less dense than liquids and solids.
That’s why air bubbles in a glass of water  move upward and escape. The solid states of matter generally  have higher densities than do the  liquids. One very important exception to this rule  is ordinary water. Water expands when  it freezes. The H2O molecules arrange  themselves in a pattern that takes up  more space than when the molecules  are in the liquid state. Therefore, ice floats in water.

Water and oil: What can you infer  about the density of these items?  Soda vs. Diet Soda: What can you  infer about the density of these items? Demonstrations: Dead Sea

Life jackets make us less dense than water, so we float.
Substances that have a density less than  water's will float in water. Substances with a  greater density than water's will sink. Life jackets make us less  dense than water, so we float. Submarines can change  depth in the water when  they remove or add water  to special tanks called  ballast tanks. When water  is removed from the tanks,  the submarine loses mass.  It floats higher in the  water. When water is  added to the tanks, the  submarine gains mass. It  sinks lower in the water  because its density is now  greater.

What is the density of a rock that has a mass of 25
What is the density of a rock that has a mass of 25.2 g  and a volume of 11.9 mL? Use the 3-step method to solve this problem: 1) Write the formula.  D = M/V 2) Plug in the numbers and units.  D = 25.2g / 11.9 mL 3) Complete the calculation and show the correct unit for density.  D = 2.1 g/mL

D stands for density, M stands for mass, and V stands for volume.
Density is a measure of how closely the  particles of a substance are packed into a  given space. Density is found by measuring mass and  volume and then dividing the mass by the  volume. The formula for density is: D = M/V D stands for density, M stands for mass,  and V stands for volume.

What is the density of a rock that has a mass of 32
What is the density of a rock that has a mass of  32.5 g and a volume of 12.8 mL? Use the 3-step method to solve this problem: 1) Write the formula.  D = M/V 2) Plug in the numbers and units. 3) Complete the calculation and show the correct unit for density.

What is the density of a rock that has a mass of 32
What is the density of a rock that has a mass of  32.5 g and a volume of 12.8 mL?

You have a rock with a volume of 15cm3 and a mass of 45 g
You have a rock with a volume of 15cm3 and a mass of 45 g. What is its density? Click for  answer You have a different rock with a volume of 30cm3 and a mass of 60g. What is its density? Click for  answer What is the density of a board whose dimensions are  5.54 cm x 10.6 cm x 199 cm and whose mass is 28.6 Kg? Show your answer in grams/cubic centimeters. Click for  answer

You have a rock with a volume of 15cm3 and a mass of 45 g
You have a rock with a volume of 15cm3 and a mass of 45 g. What is its density? Back to  Problems

You have a different rock with a volume of 30cm3 and a mass of 60g
You have a different rock with a volume of 30cm3 and a mass of 60g. What is its density? Back to  Problems

What is the density of a board whose dimensions are 5. 54 cm x 10
What is the density of a board whose dimensions are  5.54 cm x 10.6 cm x 199 cm and whose mass is 28.6 Kg? D = M/V 5.54 cm x 10.6 cm x 199 cm = cm3 cm3 28.6 Kg D= kg/cm3

D= kg/cm3 k   h   da   g    d   c   m D = 2.45 g /cm3 Back to  Problems

Substance Density (g/cm3) Platinum 21.4 Seawater 1.025 Gold 19.3 Water 1.00 Mercury 13.6 Ice 0.92 Lead 11.3 Oil 0.90 Silver 10.5 Paraffin (wax) 0.87 Copper 8.9 Gasoline 0.7 Brass 8.5 Wood (oak) Iron 7.9 Wood (pine) 0.4 Steel 7.8 Cork 0.24 Aluminum 2.7 Oxygen 0.0014 Marble 2.69 Air 0.0013 Rubber 1.1 Helium 0.0002

Work these problems in your notebook.....
1. A man is buying a copper bowl because he heard it is the best material to whip egg whites in. If the bowl has a mass of 142 g and a volume of mL, is it a real copper bowl?. 2. What volume would a gram sample of air occupy if the density of air is 1.29g/L? 3. Explain the beaker in the front of the room in terms of density.

1. A man is buying a copper bowl because he heard it is the best material to whip egg whites in. If the bowl has a mass of 142 g and a volume of mL, is it a real copper bowl? D= 142g / mL D= 8.9 g/mL Is it copper? YES! 2. What volume would a gram sample of air occupy if the density of air is 1.29g/L? D= M/V 1.29 g/L = g/ V make it simple 12=36/3 1.29 g/L = 0.451g/ .349 L

3. Explain the beaker in the front of the room in terms of density.
The yellow liquid at the top of the beaker is less dense than the other substances. The bluish substance is more dense than the top substance, but less dense than the bottom substance. The red bottom substance is the most dense.

Together, we can feed the world.
Essays must be between 700 to 1,000 words in length, include a list of research sources, and fall under one of these four categories: Together, we can feed the world. Together, we can build a secure energy future. Together, we can protect people and the environment. Together, we can be innovative anywhere. Dupont Science Essay Challenge

Write the following in each line, from most dense to least dense....
water, oil, ice gasoline, mercury, iron air, oxygen, helium sea water, ice, water

water, ice, oil mercury, iron , gasoline  oxygen, air, helium seawater, water, ice

Acrylic-clear Aluminum- shiny silver Brass- gold colored Copper- copper, reddish Oak-darker wood Pine-lighter wood Polypropylene-cloudy PVC-dark gray Steel-lighter gray, metallic, heavy

D=M/V Acrylic Substance H Density (g/cm3) Sink or Float? Aluminum
Mass  (g) L (cm) W H Volume (cm3) Density  (g/cm3) Sink or  Float? Acrylic Aluminum Brass Copper Oak Pine Polypropylene PVC Steel D=M/V WRITE EQUATIONS IN MARGIN

Acrylic Substance W (cm) H (cm) Volume (cm3) Density (g/cm3)
Mass (g) L (cm) W (cm) H (cm) Volume (cm3) Density (g/cm3) Sink or  Float? Acrylic 18 g 2.5cm 15.6 cm3 g/cm3 S Aluminum 43 g 2.7 g/cm3 Brass 134 g g/cm3 Copper 144.3 g 8.94 g/cm3 Oak 11.0 g g/cm3 F Pine 7.5 g g/cm3 Polypropylene 15 g g/cm3 PVC 22.2 g g/cm3 Steel 126.2 g 7.9 g/cm3

Density Lab INTRO: Understanding the concept of density is very important in the world of science as well is in our  everyday lives. Scientists use density calculations to help  analyze how “tightly packed” a material’s particles are.  They also use this calculation to be able to identify  various materials due to the fact that each substance has  a unique density. In our lives, we use the concept of  density to understand the relationship between different  types of materials. We use terms such as hardness or  heaviness to describe the density of various items in our  daily language. PURPOSE: The purpose of this lab is for you to practice gathering mass and volume measurements as well as to use  your collected data to make density calculations.

Substance Mass(g) Volume (cm3 or mL) How you  found  volume Density (g/ml or  g/cm3(three-step  method) Glycerine Methyl  Alcohol Wood Rubber  Stopper Wax Rock  (Granite) Mineral Oil Water

APPLYING WHAT WE HAVE LEARNED
Would gasoline float OR sink if mixed with water? _______________ Would an ice cube float OR sink if dropped in oil? _______________ Does helium gas float OR sink in air? _______________ Mercury is a liquid at room temperature. Would an iron bolt float OR sink in mercury? _______________ Write the formula for density: ________________________________________ What equipment is used to measure an item’s volume? ______________________ What label(s) do we commonly use to represent volume? ____________________ What equipment is used to measure a substance’s mass? _____________________ What label do we commonly use to represent mass? _______________ Is it easier to measure the volume of a liquid or a solid? Explain your answer.  __________________________________________________________________ __________________________________________________________________ Do you feel that this lab has helped you develop a better understanding of the concept of density? Explain.

Density Worksheet Density is the ratio of the mass of the substance to the volume of the substance at a given temperature. Density has units of g/ cm3 or g/cc or g/mL for liquids and solids, and g/L for gases. SHOW YOUR WORK! 1. A gold-colored ring has a mass of 18.9 grams and a volume of 1.12 mL. Is the ring pure gold? (The density of gold is 19.3 g/mL.) 2. What volume would a gram sample of air occupy if the density of air is 1.29 g/L? 1.29g/L = 0.871g / V (4= 12/3) .871g/1.29g/L= .675 L D=18.9g / 1.12 mL D= g/mL

D= . 95 Yes, pumice will float in water!
3. Pumice is volcanic rock that contains many trapped air bubbles. A 225 gram sample occupied mL. What is the density of pumice? Will pumice float on water? D = 225g/236.6mL D= Yes, pumice will float in water! 4. A cup of sugar has a volume of 237 mL. What is the mass of the cup of sugar if the density is 1.59 g/mL? 1.59g/mL = m / 237 mL 9 = 27/3 1.59 x 237 = m = g

5. From their density values, decide whether each of the following substances will sink or float when placed in sea water, which has a density of g/mL. Float Gasoline 0.66 g/m Sink Mercury 10.6 g/mL Float Cork 0.26 g/mL 6. A sample of lead is found to have a mass of 32.6 g. A graduated cylinder contains 2.8 mL of water. After the lead sample is added to the cylinder the water level reads 5.7 mL. Calculate the density of the lead sample. 5.7 mL -2.8 mL 2.9 mL D= 32.6 g / 2.9 mL D=11.24 g/mL

Mass to Volume must be greater than 1 g/mL 450cm3 = 450 mL
7. A little aluminum boat (mass of g) has a volume of cm3. The boat is place in a small pool of water and carefully filled with pennies. If each penny has a mass of 2.50 g, how many pennies can be added to the boat before it sinks? Mass to Volume must be greater than 1 g/mL 450cm3 = 450 mL needs to be greater than 450 g to sink 450 g g of boat = g 435.5 g/ 2.5 g (penny) 174.2 pennies to equal density 175 pennies to sink da boat!

8. Density varies with change in temperature. Why?
If the temperature changes, then the particles move further apart, cause thermal expansion to occur, which would make a higher volume, which would cause a change in density.

9. The King of Artemesia was given a gift of a crown of gold, but he suspected that he was being fooled. He asked his court scientist (that’s you) to prove if the crown was really gold or not. You found the mass of the crown was g. The volume of the crown was 53.2 ml. Is the crown made of gold? Include as much detail as you possibly can to prove your point. Use your Density Reading for help. If the crown is not made of gold, what material is it made of? How do you know? D= g / 53.2 mL D = 8.50 g/mL The crown can not be gold, as the density of gold is 19.3 g/mL. With a density of 8.5 g/mL, the crown must be made out of brass. Brass looks like gold, but is not gold at all! Brass is made up of an alloy of zinc and copper.