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

The Big Question How can we use mass and volume to prove whether or not a substance is gold? Unit 1 • Investigation I

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

You will be able to: Find the mass, volume, and density of solid objects. Unit 1 • Investigation I

Notes 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. Unit 1 • Investigation I

Units for mass and volume Measured in grams (g) for chemistry Volume Measured 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

Notes 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). Unit 1 • Investigation I

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

(cont.) Data and Calculations Metal Mass (g) Volume of water (mL) Volume of water with metal (mL) Volume of metal (mL) 2-inch long gold-colored rod 2-inch long silver-colored rod 4-inch long silver-colored rod (cont.) Unit 1 • Investigation I

Once you have determined the density of your objects: Determine what the objects are made out of using the following density data. 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? Was there a difference of density between the large and small aluminum rods? Explain

(cont.) 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 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. Unit 1 • Investigation I

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.

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. Unit 1 • Investigation I