1. Challenge 2 L. LaRosa http://www.middleschoolscience.com for T. Trimpe 2008 http://sciencespot.net/

2. The International System of Units  In the late 1700s, the French Academy of Sciences set out to make a simple and reliable measurement system. This system is now the International System of Units (SI).  Because all SI units are expressed in multiples of 10, changing from one unit to another is easy.

3. MASS  Mass can be defined as the amount of matter in an object. The kilogram is the basic SI unit for mass.  The kilogram is used to describe the mass of large objects.  1000 g = 1 kg  1 mg =.000001 kg  1 metric ton = 1000 kg

4. VOLUME  Volume is the amount of space that something occupies.  Liquid volume is expressed in liters (L).  Volumes of solids are expressed as cubic centimeters (cm 3 )  1 L = 1000 ml  1 ml = 1 cm 3

5. What is Density?  DENSITY is a physical property of matter, as each element and compound has a unique density associated with it.  For example the known density of water is 1 g /ml.  You can think of density in a qualitative manner as the measure of the relative "heaviness" of objects with a constant volume.

6. Density Formula  Density is defined as the amount of matter in a given volume. Density = mass volume Units for density may be seen as g/ml or g/cm3

7. Density in Comparison to Water  In chemistry, the density of many substances is compared to the density of water. Does an object float on water or sink in the water? If an object such as a piece of wood floats on water it is less dense than water vs. if a rock sinks, it is more dense than water.

8. Will it float in water? Determine if the following shapes will float in water by calculating the density for each item. D = M / V Mass: 15 g Volume: 20 mL Mass: 1000 g Volume: 50 mL Mass: 225 g Volume: 100 mL Mass: 10 g Volume: 200 mL www.middleschoolscience.comwww.middleschoolscience.com 2008

9. Will it float in water? Determine if the following shapes will float in water by calculating the density for each item. D = M / V Mass: 15 g Volume: 20 mL Density: 0.75 g/mL Mass: 1000 g Volume: 50 mL Density: 20.0 g/mL Mass: 225 g Volume: 100 mL Density: 2.25 g/mL Mass: 10 g Volume: 200 mL Density: 0.05 g/mL www.middleschoolscience.comwww.middleschoolscience.com 2008 If the density is less than 1.0 g/cm 3 then it will float. 1 g/mL = 1 g/cm 3