Density Miss Sauer’s 7 th Grade Science

Do Now: 1. When you were little, you heard fairytales such as “Hanzel and Gretyl” where you had to envision a dark, dense forest. Draw a dark, dense forest.

Do Now: 1. What makes a forest dense? More trees in the same amount of space.

Hold up Your Green Side for Green & Red Side for Blue

Let’s Think About What We Know… Are these boxes the same size? What vocabulary word refers to the amount of space something takes up?

Term to Remember: Volume The amount of space that matter occupies.

Let’s Think About What We Know… Are there the same amount of circles in these boxes? What vocabulary word refers to the amount of matter in an object?

Term to Remember: Mass A measure of how much matter is in an object.

Formula for Density:

Volume for both is the same. Mass for the blue? Mass for the green?

In helping others less fortunate, we packed these boxes. What makes one box more dense than another?

Everybody Loves Density!!!

Density The measurement of how much mass of a substance is contained in a given volume. Mass/Volume I Density

Units for Density Problems

What is my Density? Mass g 2.300g 3.25g Volume 50mL 15mL 5cm 3 Complete the following questions on a separate sheet of paper Density 10 g/mL 20 g/mL 5 g/cm 3

Learning Check 1 Osmium is a very dense metal. What is its density in g/cm 3 if g of the metal occupies a volume of 2.22cm 3 ? 1) 2.25 g/cm 3 2)22.5 g/cm 3 3)111 g/cm 3 lecturePLUS Timberlake 18 Answer: 2) 22.5 g/cm 3

Solution 1 2) Placing the mass and volume of the osmium metal into the density setup, we obtain D = mass = g = volume 2.22 cm 3 = g/cm 3 = 22.5 g/cm 3 lecturePLUS Timberlake 19

Density Tower

Which is more dense, the cork or the rock? Why?

Learning Check 2 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) lecturePLUS Timberlake 22 K K W W W V V V K Answer: 1) 0.91, 1.0, 1.4 g/mL

Solution 2 (W) water (1.0 g/mL) lecturePLUS Timberlake 23 K W V (K) Karo syrup (1.4 g/mL) (V) vegetable oil (0.91 g/mL) 1)

Density Within the Layers of Earth: What do you notice about the density as you travel from the crust inward to the inner core? Depth Density (g/cm 3 ) Direct Relationship What kind of relationship is this?

Density Density describes how much mass is in a given volume of a material.

Density Solids, liquids and gases are matter, so they all have density. NO MATTER WHAT SIZE, whether it is the size of a lab table or a notebook, THE DENSITY OF AN OBJECT IS ALWAYS THE SAME. Example: steel is ALWAYS 7.8 g/mL, no matter the size of the sample.

Determining Density To find the density of a material, you need to know the mass and volume of a solid sample of the material. 1. Mass is measured with a balance or scale. 2. Use the displacement method (for liquids / irregular shaped objects) or calculate the volume (for regular shaped objects). V of object = V final – V initial V = l x w x h

Calculating Density: Whatever you are solving for, you can cover that letter and then use the positions of the remaining letters to determine the formula.

Triangle Method:

Using the Triangle Method, Determine the Formulas for: Volume, Mass, & Density

How Far Down an Object Goes in Water Depends on It’s Density: Density is Down in the water.

List These Materials in Order from Most Dense to Least Dense:

Demo:

Lab: Go over the next (2) slides for the lab as well.

Review: Qualitative Observations vs. Quantitative Observations Qualitative Observations are descriptions that DO NOT use numbers. For Example, if you report colors, smells, tastes, textures, or sounds, you are making qualitative observations. Quantitative Observations are descriptions that do include numbers. For Example, if you count objects or measure them with standard units, you are making quantitative observations.

Qualitative vs. Quantitative Observations – USE THE ROOT WORDS TO HELP YOU Qualitative Observations QUALITY or QUALITITES something possesses. Quantitative Observations QUANTITY of something / how much.

Closure Questions What is density? How is density calculated? What are the units for density? How do you use the triangle method to solve for unknowns in the density formula? If a large piece of aluminum has a density of 2.7 g/mL, what would the density be if the sample were cut in half? What is the density of water? How does density effect positions of liquids poured in the same container?

What is my Density? Mass g 2.300g 3.25g Volume 50mL 15mL 5cm 3 Complete the following questions on a separate sheet of paper Density