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Objective: Introduction to Density

Objective: Introduction to Density Density is a math relationship that is equal to the mass of a substance divided by it’s volume. Density is a constant for all elements, and all pure substances. That means no matter how much you have in mass, you will have a corresponding volume. Density = .

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Objective: Introduction to Density

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  1. Objective: Introduction to Density Density is a math relationship that is equal to the mass of a substance divided by it’s volume. Density is a constant for all elements, and all pure substances. That means no matter how much you have in mass, you will have a corresponding volume. Density = Mass (in grams) Volume (in cm3) Look at the little box, it’s one cubic centimeter. 1 cm3 = 1 milliliter

  2. Since 1 cm3 = 1 milliliter or 1 cm3 = 1 mL • Then this is true too: • grams/cm3 = grams/ mL these units are both ok • 10g/cm3= 10 g/ mL • 150 g/cm3 = 150 g/ mL • 1750 g/cm3 = 1750 g/ mL

  3. Copy these 4 density values for these 4 metals (you’ll need them for lab today, and tomorrow.

  4. To measure volume of a regular object, like the black table tops out back, you can use the formula V = L x W x H to calculate the volume (easy) But if the shape of your object is weird, or irregular in shape, that is not going to fly. We can use a graduated cylinder, and use the water displacementmethod to determine the volume.

  5. Reading the cylinder is tricky business. Each line is equal to one milliliter. You must look hard, and read to the nearest milliliter, then estimate out one more place. You can’t read this as 53 mL and be correct. You must read it as 52.9 mL, or maybe you see 52.8 mL, or, if your eyes are really bad, it might even be 53.0 mL. BUT: it can’t be to the nearest whole mL, it has to be to the nearest 10th of an mL. Not to the 100th place either!

  6. Measure the water in the tube carefully, and write that number down. Put the metal in the tube without splashing out any water (be careful) Re-measure the water, and subtract the starting water volume. The difference between end and start is the volume of the metal, which displaced the water upwards. What’s a MENISCUS?

  7. We will mass the metal DRY, and first, then get the volume. We will calculate the density of one metal now. Get a partner, go to a set up in the back. Weigh ALL of the metal present, even if there are five pieces. Get the volume of ALL the metal that you put on the scale. Dump water, dry metal, put metal back into the beaker. Calculate the density of your metal. Using your measured value for density, and the actual density values from before, calculate your percent error. Write the formula first, fill in the MV and the AV, and do the math. Who has the lowest %Error? (round to 3 digits total)

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