All that Glitters

Density of solids

All that glitters…

• In order to distinguish one form of matter from another, it is often necessary to examine the properties of each substance.

King Hiero and the crown

King Hiero commissioned a golden crown from a group of goldsmiths.

Over time, he became convinced that the artisans cheated him by not making the crown out of solid gold.

He asked Archimedes to determine if the crown was made out of solid gold WITHOUT damaging it in any way

Chem Catalyst

• Archimedes did think of a way to successfully test whether the crown was fake. – How did he do it?– What equipment did he need if he did the same

experiment today?– What information would he need to derive from

the data?

Answer

• Water• Measured Container (graduated

cylinder/beaker)• Scale to measure mass

Unit 1 • Investigation I

The Big Question

– How can we use mass and volume to prove whether or not a substance is gold?

Simple answer

• There is a intrinsic property of gold that sets it apart from all other pure materials…

• It’s Density

• Intrinsic means that any size piece of gold has the same value for that property

Unit 1 • Investigation I

You will be able to:

– Find the mass, volume, and density of solid objects.

Unit 1 • Investigation I

– Mass is the amount of stuff or

substance. We measure mass by measuring weight on a scale or balance.

– Volume refers to the amount of space occupied by a substance.

Notes

Units for mass and volume

• Mass – Measured in grams (g) for chemistry

VolumeMeasured in cm3 for solids and ml for liquids

1 ml = 1 cm3

How to find mass or volume

• To find mass, use a electric balance or scale

• To find the volume, either calculate using - A formula

- A graduated cylinder:Fill cylinder to a certain level (note amount). Add object (level of water should rise). Difference in amounts equals volume of object

Density

Measure of how much mass of an object is placed within the volume it occupies

How much stuff is in a certain space

A ratio

Density equation

• Density = mass / volume

• D = m/V (remember the heart formula!)

• Units for density: g/cm3 = g/ml

Unit 1 • Investigation I

– Density is defined as the mass per unit volume or how much “stuff” there is in a certain space.

d = m v (heart)

– The intrinsic property of a substance is a property that doesn’t depend on size and shape (for the same temperature).

Notes

groups

• Up to eight

• Once selected, Write full names in book

• Create materials list and Chart

Each group gets…

• One graduated cylinder (plastic)• One griffin Beaker (250 ml), with water• A question/density data sheet• A eye dropper (for measuring with water)

• 6 objects from the tan box in the front of the room, 3 of which will be a gold 2 inch rod, silver 2 inch rod and silver 4 inch rod

Unit 1 • Investigation I

Data and Calculations

Metal Mass

(g)

Volume of

water

(mL)

Volume of

water with

metal (mL)

Volume of

metal

(mL)

2-inch longgold-colored rod

2-inch longsilver-colored rod

4-inch longsilver-colored rod

(cont.)

(cont.)

Once you have determined the density of your objects:

1) Determine what the objects are made out of using the following density data.

2) The small silver rod was made out of aluminum and gold rod is brass. How close are your calculated values to the stated values in the table?

3) Was there a difference of density between the large and small aluminum rods? Explain

Unit 1 • Investigation I

Densities of metals

copper zinc gold aluminum brass

9.0 g/mL

lead

11.3 g/ml

7.1 g/mL

steel

7.67 g/ml

19.3

g/mL

silver

10.5

g/ml

2.7 g/mL

nickel

8.9 g/ml

8.0-8.6

g/ml

Iron

7.7 g/ml

(cont.)

Unit 1 • Investigation I

Activity

• Purpose: It is not always easy to tell one form of matter from another. This activity will show you how to differentiate between different forms of matter by examining density, one of the physical properties of matter.

• density = mass ÷ volume

(cont.)

Unit 1 • Investigation I

Making Sense

– Could you use density information to determine if the golden penny you made in class is gold? Why or why not?

Unit 1 • Investigation I

Check-In• In 1999 the United States Mint produced

a coin called the Golden Dollar. It features an image of Sacagawea, the famous Native American guide for Lewis and Clark. It has a mass of 9.8 g and a volume of 1.1 ml. – What is the density of this coin?– The density of gold is 19.4 g/ml. Is this

coin truly gold? Explain.

Check in question 2

a) What determines if a person floats or sinks in a pool?

b) If you take a deep breath an hold it, do your chances improve for being able to float? Explain your answer.

Unit 1 • Investigation I

Wrap-Up

– Density is an intrinsic physical property of matter. It is a measure of the mass per unit of volume of a substance.

– One substance can be distinguished from another by examining its intrinsic physical properties.