1. What is Density?

2. Chemistry – How many particles per unit area?

3. Units for Density Density = mass/volume or D = m/v. Density is the mass of an object divided by the volume Mass = gram (g) Volume = centimeters cubed cm 3 or ml So, the overall units for density are g/cm 3 or g/ml

4. Do Not Write Density and Phases of Matter Phases of matter are solids, liquids, gasses Solids are the most dense objects because they have more particles close together and very little movement. Liquids are next because the particles have more movement and are moving (flowing) around. The least dense liquid will collect on top of the most dense object. Gasses are least dense because the particles are moving quickly past each other and are spaced far apart.

6. Regular Shaped Object These are objects with fixed shapes, having defined edges like a rectangle or a square To find the mass use a triple beam balance or an electronic balance using grams as the unit. To find the volume you have to measure 3 sides of the object: length, width, height and multiply the numbers together. L x W x H = _____ cm 3. Note that cm 3 is the volume unit for a regular shaped object Density unit for a RSO will be g/cm 3

7. L x W x H (cm)

8. Irregular Shaped Object These are objects with no fixed shape and do not have defined edges like a rock or a cylinder. To find the mass use a triple beam balance or an electronic balance using grams as the unit. To find the volume you have to use the Water Displacement Method. Using a graduated cylinder, place enough water in the cylinder to cover the object. Place the ISO in the cylinder. The water level will rise. The difference between the starting volume and the ending volume will be the volume of the object. So, use this equation: ending volume (EV) – starting volume (SV) = volume of object in ml. Density unit for an ISO will be g/ml

9. Liquid Liquids have no fixed shape because they take the shape of the container. To measure the mass of a liquid, first mass an empty graduated cylinder in grams then pour some liquid into the cylinder and mass again. The difference between the ending mass and starting mass is the mass of the liquid. So, use this equation: ending mass (EM) – starting mass (SM) = mass of object in g. To get the volume just read the meniscus on the graduated cylinder.

10. Measuring Liquid Volume Images created at http://www.standards.dfes.gov.uk/primaryframework/downloads/SWF/measuring_cylinder.swf What is the volume of water in each cylinder? Pay attention to the scales for each cylinder.

11. Measuring Solid Volume Click here for an online activity about volumeClick here for an online activity about volume. Choose Lessons  Volume & Displacement 10 cm 9 cm 8 cm We can measure the volume of regular object using the formula length x width x height. _____ X _____ X _____ = _____ http://resources.edb.gov.hk/~s1sci/R_S1Science/sp/e n/syllabus/unit14/new/testingmain1.htm We can measure the volume of irregular object using water displacement. Amount of H 2 O with object = ______ About of H 2 O without object = ______ Difference = Volume = ______

13. Find the density of the object below. The mass An object was dropped into a graduated cylinder that contained 20 mL. Determine the volume of that object. The object was placed on a triple beam balance. Image from http://ritter.tea.state.tx.us/Image from http://genchem.rutgers.edu/bal3b2.html

14. The solution … Volume = Volume of water & object – volume of water Volume = 43 mL – 20 mL V = 23 mL M = 373.3 g Density = Mass ÷ Volume D = 373.3 g ÷ 23 mL D = 16.23 g/mL

15. Find the density of the box below. 12.5 cm 5.6 cm Mass 456 g

16. The solution … Volume = length x width x height V = 12.5 cm x 5.6 cm x 5.6 cm V = 392 cm 3 M = 456 g Density = Mass ÷ Volume D = 456 g ÷ 392 cm 3 D = 1.16 g/cm 3 **The box would sink!

17. Practice A student in lab measured the mass of a rectangle to be 23.7 g. The length was 21.0 cm. The width was 7.0 cm. The height was 5.0 cm. What is the density of the object? Show all work and units!!!

18. V = L x W x H = 21.0cm x 7.0cm x 5.0cm = 735.0 cm 3 Answer D = Mass = 23.7 g = 0.032 g/cm 3 Volume 735cm 3

19. Practice Malia found a 10 g diamond in a mine in West Virginia. She wanted to know the volume of the diamond so she place 50 ml of water in a 100 ml graduated cylinder and after placing the diamond in the cylinder the water level rose to 75 ml. What is the density of the diamond? Show all work and units!!!

20. D = Mass =10 g = 0.4 g/ml Volume 25 ml Answer V = EV-SV = 75ml – 50ml = 25ml 1 Sig Fig

21. Practice Jacob massed an empty graduated cylinder to be 58.0 g. He then put 28.0 ml of rubbing alcohol in a graduated cylinder. He then measured the object and the graduated cylinder to be 78.0 g. What is the density of the rubbing alcohol? Show all work and units!!!

22. D = Mass = 20.0 g = 0.714 g/ml Volume 28.0 ml Answer M = EM-SM = M = 78.0g – 58.0g = 20.0g 3 Sig Figs

23. M = V x D V = Mass Density D = Mass Volume Some questions ask you to find mass or volume, so you will need to rearrange the original equation