T. Trimpe 2008 http://sciencespot.net/ Lesson 2: Mass T. Trimpe 2008 http://sciencespot.net/

Mass is a measure of the quantity of (stuff) matter present Units of Mass Mass is a measure of the quantity of (stuff) matter present Weight is a force that measures the pull by gravity on matter- it changes with location Mass is constant, regardless of location

Weight is the Pull of Gravity Weight is a measure of the pull of gravity. Weight is measured with a spring that is compressed or stretched. 3

All Matter has Gravity The elephant has more matter so it has more mass, so it has more gravity. Even dust is matter so it pulls other dust together by gravity. 4

Mass Does Not Change While on the Earth I will place an object on one side of a balance and an equal amount of water on the other side. Now I will travel to the moon. Once on the moon I will repeat the experiment. Although the moon pulls 1/6th as hard on the object, it also pulls 1/6th as hard on the water, so it still balances. For this reason scientists prefer to measure matter by it’s mass not weight. 5

Units for Measuring Mass Mass – amount of substance present. Does not change when going to the moon. Mass is measured on a pan balance. Weight – related to gravity. Your weight is about 1/3 on the moon and 3X on Jupiter. As gravity increases your weight increases. Pull of gravity on jet fighter planes – make your arms and legs very heavy and g-forces increase. Weight is measured on a scale. 1 kg = 2.20 lb Timberlake, Chemistry 7th Edition, page 3

Quantities of Mass Giga- Mega- Kilo- base milli- micro- nano- pico- Earth’s atmosphere to 2500 km 1018 g 1015 g 1012 g Ocean liner Giga- Mega- Kilo- base milli- micro- nano- pico- femto- atomo- 109 g Indian elephant 106 g Average human 103 g 1.0 liter of water 100 g 10-3 g 10-6 g Grain of table salt 10-9 g 10-12 g 10-15 g 10-18 g Typical protein 10-21 g Uranium atom 10-24 g Water molecule Kelter, Carr, Scott, Chemistry A Wolrd of Choices 1999, page 25

Mass 1 kg = 2.2 lbs 1 g = 1 paper clip 1 mg = 10 grains of salt or 2 drops of water.

English vs. Metric Units 1 pound = 453.6 grams Which is larger? 1. 1 Pound or 100 Grams 2. 1 Kilogram or 1 Pound 3. 1 Ounce or 1000 Milligrams 100 kilogram = 220 pounds 1 ounce of gold = 28,349.5 milligrams

Metric Units kg g cg mg Kilogram Prototype Mass refers to the amount of matter in an object. The base unit of mass in the metric system in the kilogram and is represented by kg. Standard: 1 kilogram is equal to the mass of the International Prototype Kilogram (IPK), a platinum-iridium cylinder kept by the BIPM at Sèvres, France. Metric Units 1 Kilogram (km) = 1000 Grams (g) 1 Gram (g) = 1000 Milligrams (mg) Click the image to watch a short video about mass. Which is larger? A. 1 kilogram or 1500 grams B. 1200 milligrams or 1 gram C. 12 milligrams or 12 kilograms D. 4 kilograms or 4500 grams Kilogram Prototype Image - http://en.wikipedia.org/wiki/Kilogram

_______ + ______ + _______ = ________ 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. 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 Top Image: http://www.southwestscales.com/Ohaus_Triple_Beam_750-SO.jpg Bottom Image: http://www.regentsprep.org/Regents/biology/units/laboratory/graphics/triplebeambalance.jpg

Measuring Mass – Triple-Beam Balance 1st – Place the object to be massed (not weighed) on the scale. 2nd – Slide the large weight to the right until the arm drops below the line. Move the rider back one groove. Make sure it “locks” into place. 3rd – Repeat this process with the top weight. When the arm moves below the line, back it up one groove. 4th – Slide the small weight on the front beam until the lines match up. 5th – Add the amounts on each beam to find the total mass to the nearest tenth of a gram. Click here to try an online activity.