Warmup 9/2/15

How do you know if you got the right answer in a lab experiment?

Objective Tonight’s Homework

To learn about calculating density hands-on

Read section 2.2 Do p 30: 1, 2, 3, 4

Lab on Mass, Volume, Density

Today we’re going to do a lab on investigatingmass, volume, and density. (In pairs)

Mr. C. is going to do an example or two with you guys, then let you loose to do the rest by yourselves.But first, let’s go over a few pre-lab questions:

1) How would you get the density for one of the wood blocks? (How are you going to measure mass and volume?)2) How would you get the density for water?3) How would you get the density for something like the glass stopper? (Hint: what would you see if you put it into a graduated cylinder of water?)

Lab on Mass, Volume, Density

To get the density for a block, we need to measureits mass and its volume. We can get mass by placing it on the scale. We can get volume by measuring the sides and multiplying.

To get the density of water, we also need mass and volume. We can get the volume by looking at the graduated cylinder and writing how many milliliters we have. To get mass, we need to compare an empty graduated cylinder with the one that has water. We need to look at their difference in mass. That’s how much the water weighs.

Lab on Mass, Volume, Density

To get the glass stopper, we need mass and volume. We can get mass by putting it on the scale. Volume is harder, though. To get volume, we need to put it in a graduated cylinder that has water. After we put it in, the water level will go up. The difference in how much it went up tells us the stopper’s volume in milliliters. Yep, we’re getting the volume of a solid in milliliters. Weird!

Lab on Mass, Volume, Density

Let’s go ahead and start setting up our lab writeup as a class.

Let’s do:Purpose

Hypothesis

Materials

Data (table)

Lab on Mass, Volume, Density

Purpose To find the density of several different materials.Hypothesis (Compare each thing to water (which equals 1). If it floats, it probably has a density less than 1. If it sinks, it’s more than 1. If it really sinks fast, maybe its 6 or 7!)Materials Plastic cube, wooden cube, glass stopper, cork, penny, water, mineral oil, scale, ruler, graduated cylinderData (table)

plastic wooden glass cork penny water oil

Mass

Volume

Density

Lab on Mass, Volume, Density

Ok. From here, you’re ready to start doing yourexperiment. Take careful measurements as you go.

Also, as you work, write down as precisely as possible what you’re doing. Later, we’ll make our procedures. Mr. C. will watch as you work, and help if you need it.

Find the density of the penny, the plastic cube, and the wood cube. (volume of a penny = ∏r2h)

Find the density of the cork and the glass stopper

Find the density of water and of the oil.

Lab on Mass, Volume, Density

Ok. From here, you’re ready to start doing yourexperiment. Take careful measurements as you go.

Also, as you work, write down as precisely as possible what you’re doing. Later, we’ll make our procedures. Mr. C. will watch as you work, and help if you need it.

Find the density of the penny, the plastic cube, and the wood cube. (volume of a penny = ∏r2h)

Find the density of the cork and the glass stopper

Find the density of water and of the oil.

Lab on Mass, Volume, Density

For our analysis, let’s look over the answers we gotand see if they make sense. For each object, tell meif the density you got was more or less what you expected. Also, tell me what you could do to make your answers better if you had to do this lab again.

For your conclusion, tell me what you learned about density.

Exit Question

What was the density of the penny?

3.0 g/cm3

4.7 g/cm3

5.5 g/cm3

6.1 g/cm3

7.2 g/cm3

8.8 g/cm3