Will the ball float on liquid mercury?

The ball floats on liquid mercury!

Why did it happen???? Mercury density = 13600kg/m3 The ball’s density = 11340kg/m3 Sinking vial - make it float

SI Units Density

Density Must (Pass) Should (Merit) Could (Distinction) Be able to calculate density from given values. Be able to suggest the order of liquids in a density ladder. Be able to explain a density ladder. Be able to calculate the density of regular objects by experimental means. Be able to manipulate and use the density triangle. Be able to calculate the density of irregular objects by experimental means.

lecturePLUS Timberlake Density Density compares the mass of an object to its volume D = mass = g or g volume mL cm3 Note: 1 mL = 1 cm3 lecturePLUS Timberlake

Density is the Mass per unit Volume What is Density? If you take the same volume of different substances, then they will weigh different amounts. Wood Water Iron 1 cm3 1 cm3 1 cm3 IRON 0.50 g 1.00 g 8.00 g Q) Which has the greatest mass and therefore the most dense? Density is the Mass per unit Volume

Density Equation: = m V m V  g or kg Mass Density = Volume gcm-3 or kgm-3 cm3 or kg3 = m V

Density Equation: Example: Q) Liquid water has a density of 1000kgm-3, while ice has density of 920kgm-3. Calculate the volume occupied by 0.25kg of each. V = m = 0.25 = 0.000250m3  1000 V = m = 0.25 = 0.000272m3  920

lecturePLUS Timberlake Learning Check D1 Osmium is a very dense metal. What is its density in g/cm3 if 50.00 g of the metal occupies a volume of 2.22cm3? 1) 2.25 g/cm3 2) 22.5 g/cm3 3) 111 g/cm3 lecturePLUS Timberlake

lecturePLUS Timberlake Solution 2) Placing the mass and volume of the osmium metal into the density setup, we obtain D = mass = 50.00 g = volume 2.22 cm3 = 22.522522 g/cm3 = 22.5 g/cm3 lecturePLUS Timberlake

Volume Displacement A solid displaces a matching volume of water when the solid is placed in water. 33 mL 25 mL

lecturePLUS Timberlake Learning Check What is the density (g/cm3) of 48 g of a metal if the metal raises the level of water in a graduated cylinder from 25 mL to 33 mL? 1) 0.2 g/ cm3 2) 6 g/m3 3) 252 g/cm3 33 mL 25 mL lecturePLUS Timberlake

lecturePLUS Timberlake Solution 2) 6 g/cm3 Volume (mL) of water displaced = 33 mL - 25 mL = 8 mL Volume of metal (cm3) = 8 mL x 1 cm3 = 8 cm3 1 mL Density of metal = mass = 48 g = 6 g/cm3 volume 8 cm3 lecturePLUS Timberlake

Learning Check3 Which diagram represents the liquid layers in the cylinder? (K) Karo syrup (1.4 g/mL), (V) vegetable oil (0.91 g/mL,) (W) water (1.0 g/mL) 1) 2) 3) K V W K V W W V K

Solution (K) Karo syrup (1.4 g/mL), (V) vegetable oil (0.91 g/mL,) (W) water (1.0 g/mL) 1) V W K

DENSITY OF A REGULAR SOLID Find the Mass of the solid on a balance. Measure the three lengths and calculate the Volume. (ie V = l x w x h ) Calculate the Density. m = 240 g 2.0 cm  = m = 240 =10.0 g/cm3 V 24 3.0 cm 4.0 cm

DENSITY OF AN IRREGULAR SOLID m = 360 g  = m = 360 =12.0 g/cm3 V 30 Find the Mass of the solid on a balance. Fill the Measuring Cylinder with Water to a known Volume. Add the Object. Work out the Volume of Water that is displaced. Calculate the Density. 80 cm3 50 cm3

DENSITY OF AN IRREGULAR SOLID OR use a Eureka Can to find the Volume. Find the mass of the solid on a balance. Add water until just overflowing. Place a Measuring Cylinder under the spout. Add the Object. Collect the Water and read off the Volume. Calculate Density m = 440 g 40.0 cm3  = m = 440 =11.0 g/cm3 V 40

Learning Check You have 3 metal samples. Which one will displace the greatest volume of water? 1 2 3 Discuss your choice with another student. 25 g Al 2.70 g/mL 45 g of gold 19.3 g/mL 75 g of Lead 11.3 g/mL

Solution 1) 25 g Al x 1 mL = 9.2 mL 2.70 g 25 g Al 2.70 g/mL

Pre-Lab How do you correctly read a graduated cylinder? What techniques can you use to measure the volume of an irregularly shaped object? What tips should you remember? How do you take the slope of a line? How is percentage error defined? Name the two general types of mathematical relationships between variables to be investigated in this lab What safety precautions must be taken for this lab

Materials Rock sample Balance Graduated cylinder(s)

Procedure Choose equipment to make and record all measurements as accurately and precisely as possible. Be sure to record the correct number of digits for your data. Obtain 2 rock samples Make sure the samples are dry and clean. Obtain their masses. Remember the uncertainty Measure the volume of the rock using the volume displacement method

4. Repeat method 2 and 3 and obtain an average 5. Calculate the volume of the rock. Repeat for the second sample.

Results Data table and calculations Sample 1 Trial 1 Trial 2 Average Initial Vol (ml) Final Vol (ml) Calculated volume (ml) Mass (g) Sample 1 Trial 1 Trial 2 Average Sample 2 Trail 1 Trail 2

More Calculations Make a single table using mass and volume, density for all samples. Display the formula and show all working. Ensure all units are correctly displayed. Obtain the class data for each group for each sort of rock sample and make another table, showing mass, volume, as well as the computation of mass x volume and mass/volume. Use the appropriate units.

Your graph will show a scatter of points, draw a line of best fit. Look at the data/calculations table, which is constant; mass x volume OR mass/vol ? What type of relationship was found in this lab? Hint: If A/B is constant, then there is a direct relationship. If AxB is constant then there is an inverse relationship. Using the above data, explain what the gradient of the line represents?

Calculate the gradient of the line Calculate the gradient of the line. You can choose any two points on a line to calculate slope, but it is best to choose them far apart. Accurately calculate your gradient. Write your final slope as a decimal, to two decimal places. Don’t forget units!!

Discussion: Answer the following questions. 1. Compare your calculated gradient from the class results to your calculated density from your own results. What is the error margin? Should a density graph go through the point (0,0)? Why or why not? Would you get the same values of slope if you just counted the number of grid lines in the rise and run (ignoring the scales on your graph)? Give one example.

Why must the samples be clean and dry to start? If I randomly picked two pure solid substances in the room, is it likely that they would have the same density? If I could take any size piece of either, could I make them have the same density? Comment on your answers. If you were given another rock sample, would you rather know its mass or its density if you wanted to find out what kind of rock it is. Explain.

Would the presence of an air bubble stuck on the submerged rock tend to make the density too high or too low? Explain. Discuss any experimental errors that could of lead to the inaccuracies in this lab. What improvements could you put in place to increase the accuracy of your results. Conclusion:

Lab Report Due: When you hand in your full lab report, make sure the pre-lab is on the top. For this lab make sure your graph is the last page of the report. Due Date: Wednesday Sept 19th. All questions will be on the PowerPoint on teacherweb.