Density: Teacher's Guide and Student Activity Sheet for Learning Experience 5

TEACHER’S GUIDE

Materials:

For each group of three students:

3 Student Activity Sheets for Learning Experience 5

Calculator

Preparation:

Read background information. A mini-lesson on using a calculator may be necessary. A mini-lesson on decimal place value and serial order of decimals may be necessary.

Basic Skills Development:

Measuring

Discussing

Gathering Data

Interpreting Data

Evaluation Strategy:

Students will calculate the density of the balls and liquids using the formula Density = Mass/Volume and place the solids and liquids in serial order by their densities.

Vocabulary:

volume

mass

density

formula

float

Objective: Students will calculate the density of solids and liquids and place the solid and liquid in serial order by density.

Can we determine the density of solids and liquids?

In Learning Experience 2, the mass of a wooden and steel ball was found. In Learning Experience 4, the volume of the steel and wooden ball through displacement was found. With the mass and volume of the balls, demonstrate the procedure to calculate the density of the wooden and steel balls using the formula Density = Mass/Volume and a calculator. Students should record the procedure and the density calculation of the wooden and steel ball on the chart on their Student Activity Sheet for Learning Experience 5.

In Learning Experience 2, students recorded the mass of the super ball, black rubber ball, and glass ball. In Learning Experience 4, students measured the volume of the super ball, black rubber ball, and glass ball through displacement. Using the chart on the Student Activity Sheet for Learning Experience 5, record the information from these previous learning experiences. Students are to now calculate the density of each ball using the formula Density = Mass/Volume and record the density for each ball on the chart. Students that have just been introduced to the topic of decimals can record the answer as they would for dollars and cents. An answer similar to 1.25 is what should be recorded on their activity sheets. The units are grams per cubic centimeter (g/cm³).

In Learning Experience 3, students measured the mass of three liquids; rubbing alcohol, water, and salt water. The volume of each liquid was 20 cubic centimeters. Students are to, again, use the formula and a calculator to calculate the density of each liquid and record the density on the chart provided on the Student Activity Sheet for Learning Experience 5.

Now that students have calculated the density for each liquid and each ball, students are to put the densities in serial order, beginning with the least dense. The order can be listed on their activity sheet.

Discussion Questions:

How did the solids and liquids order by density? (Rubbing Alcohol, water, salt water)

How would the wooden balls and steel balls fit in the order? (Wooden balls, alcohol, water, salt water, steel balls)

Based on the order you placed the solids and liquids in, predict which balls will sink or float in each of the liquids. For example, will the wooden ball sink or float in rubbing alcohol or water or salt water? Will the rubber ball sink or float in rubbing alcohol or water or salt water? Will the glass ball sink or float in rubbing alcohol or water or salt water? Will the steel ball sink or float in rubbing alcohol or water or salt water? Explain your predictions. (Make predictions)

Students can then test their predictions with the materials provided. Discuss the results.

STUDENT ACTIVITY SHEET for Learning Experience 5

Name_________________

DENSITY

Density is the measure of the “compactness” of a material. It is the ratio of mass to volume for any material. It is usually measured in grams per cubic centimeter (g/cc, g/cm³) and tells how much matter is packed into a given space. Density is not a simple comparison of the “heaviness” or “lightness” of materials. It is instead, a comparison of the “heaviness” or “lightness” of the same volume of material (mass per unit volume). The density of a material is determined by the masses of the atoms in the material and the amount of space between the atoms. Gases have a low density not only because the atoms making up the gases have a small mass, but also because there is a large amount of space between the atoms. The heavy metals like gold, lead, and uranium are very dense because the atoms they are composed of are massive and spaced closely together.

To calculate density, we divide the mass of the material in grams by its volume in cubic centimeters. We might just as well divide the mass in kilograms by the volume in liters, or the mass in metric tons by the volume in cubic meters, the answer in each case would be numerically the same. The density of an object equals its weight divided by its volume (D = M/V).

On the following chart, fill in the mass and volume of each ball from the previous learning experiences. Use the formula for density (Density = Mass/Volume or Mass ÷ Volume) and your calculator to find the density of the wooden ball and steel ball. Write your answers in the last column inside the chart below. (The formula is Density = Mass/Volume.)

After calculating the mass, volume, and density of the wooden and steel balls, refer to Learning Experience 2 and Learning Experience 4 to fill-in the mass and volume of the super ball, black rubber ball, and glass ball in the chart below. Use the formula for density, Density = Mass/Volume, and your calculator to get the density of each ball.

After calculating the mass, volume, and density of each of the solids, refer to Learning Experience 3 and Learning Experience 4 to fill-in the mass and volume of each of the liquids in the chart below. Use the formula for density, Density = Mass/Volume and your calculator to calculate the density of each liquid.

Now that you have calculated the densities of the three balls, (glass, black rubber, and super) and the three liquids (water, rubbing alcohol, and salt water) serial order the densities beginning with the least dense.