Middle+School+Chemistry+Chapter+3

=Chapter 3, Lesson 1: What is Density?= media type="custom" key="24097072"

Key Concepts

 * Density is a characteristic property of a substance
 * The density of a substance is the relationship between the mass of the substance and how much space it takes up (volume)
 * The mass of atoms, their size, and how they are arranged determine the density of a substance
 * Density equals the mass of the substance divided by its volume; D=m/v
 * Objects with the same volume but different mass have different densities

Objective
Students will be able to calculate the density of different cubes and use these values to identify the substance each cube is made of. Students will be able to explain that the size, mass, and arrangement of the atoms or molecules of a substance determines its density.

Materials Needed

 * cubes
 * balance
 * calculator

//** Remember that volume and area are two different things. Area is measured in two dimensions (length x width) with an answer in cm². Area is a measure of the amount of surface. But volume is measured in three dimensions (length x width x height) with an answer in cm³. Volume is a measure of the entire object, including the surface and all the space the object takes up. **//


 * 1) Watch the demonstration and record your observations on your activity sheet.
 * 2) Watch the following animation: media type="file" key="cube.swf" width="360" height="270"
 * 3) Measure and confirm the volume of the cubes. Determine their mass & density
 * 4) Complete the chart on your activity sheet for each cube sample
 * 5) Compare the values you found with the given value in the chart to identify which cube is made out of which material. Complete the chart.
 * Most common metals like aluminum, copper, and iron are more dense than plastic or wood. The atoms that make up metals are generally heavier than the atoms in plastic and wood and they are packed closer together. **


 * Most plastics are less dense than metal but can have similar density to wood. Plastics are made from individual molecules bonded together into long chains called polymers. These polymer chains are arranged and packed together to make the plastic.**


 * Wood is made mostly from carbon, hydrogen, and oxygen atoms bonded together into a molecule called glucose. These glucose molecules are bonded together to form long chains call cellulose. many cellulose molecules stacked together give wood its structure and density.**

6. Complete the //Take It Further// portion of your activity sheet.

=Chapter 3, Lesson 2: Finding Volume - The Water Displacement Method= media type="custom" key="24117812"

Key Concepts

 * A submerged object displaces a volume of liquid equal to the volume of the object.
 * One milliliter (1 mL) of water has a volume of 1 cubic centimeter (1 cm³)
 * Different atoms have different sizes and masses
 * Atoms on the periodic table are arranged in order according to the number of protons in the nucleus
 * Even though an atom may be smaller than another atom, it might have more mass
 * The mass of atoms, their size, and how they are arranged determine the density of a substance
 * Density equals the mass of the object divided by its volume; D=m/v
 * Objects with the same mass but different volume have different densities

Objective
Students will be able to explain that materials have characteristic densities because of the different mass, size, and arrangement of their atoms. Student swill be able to use the volume displacement method to find the volume of an object.

Materials Needed

 * set of 5 different rods that all have the same mass
 * graduated cylinder, 100 mL
 * water
 * calculator

//**Remember that 1 ml is the same as 1 cm³**//


 * 1) Use your clear plastic cube to do the following experiment: Record your results in your science notebook
 * Measure the dimensions of the cube with a ruler and calculate the volume in cubic centimeters.
 * Fill the cube up with water.
 * Pour the water into a large graduated cylinder.
 * 1) Examine the 5 rids. These rods all have the same mass. Make a prediction in your science notebook about which rod is the most dense? Least dense? In between? Write your answers on your activity sheet.
 * 2) Watch the following animation: media type="file" key="water_displacement.swf" width="360" height="270"
 * 3) Measure the volume of each of the 5 rods and determine their density. Complete the charts on your activity sheet.
 * 4) Did your experiment support the prediction you made?
 * 5) [[image:atomic.jpg]]
 * 6) [[image:Poly1.jpg]] Polyethylene is made of long molecules of only carbon and hydrogen atoms.
 * 7) [[image:poly2.jpg]]Polyvinyl chloride is made up of carbon, hydrogen, and chlorine atoms.
 * 8) [[image:brass.jpg]]Brass is a combination of copper and zinc atoms.
 * 9) Refer to the illustration of Calcium and Sulfur on your activity sheet. Complete the //Take It Further// section.

=Chapter 3, Lesson 3: Density of Water= media type="custom" key="24118884"

Key Concepts

 * Just like solids, liquids also have their own characteristic density
 * The volume of a liquid can be measured directly with a graduated cylinder
 * The molecules of different liquids have different size and mass
 * The mass and size of the molecules in a liquid and how closely they are packed together determine the density of the liquid
 * Just like a solid, the density of a liquid equals the mass of the liquid divided by its volume; D=m/v
 * The density of water is 1 gram per cubic centimeter
 * The density of a substance is the same regardless of the size of the sample

Objective
Students will be able to measure the volume and mass of water and calculate its density. Students will be able to explain that since any volume of water always has the same density, at a given temperature, that density is a characteristic property of water.

Materials Needed

 * graduated cylinder
 * water
 * balance
 * dropper
 * two identical large containers

Meniscus


 * 1) Fill, almost to the top, one of the large containers. Put 1 cup of water in the other. Now lift both containers. Which bucket appears to have more mass? Complete the demonstration part of your activity sheet.
 * 2) What two things do you need to know in order to find the density of water? How could you measure the volume? How can you measure the mass of water?
 * 3) Complete the experiment listed on your activity sheet. Record your observations.
 * 4) Graph your data on your activity sheet
 * 5) [[image:density_of_water.jpg]] Water molecules all have the same mass and size.
 * 6) Watch the following and complete the //Explain it with Atoms & Molecules// section of your activity sheetmedia type="file" key="liquid_water.wmv" width="300" height="300"
 * 7) Complete the //Take It Further// section of your activity sheet

=Chapter 3, Lesson 4: Density: Sink and Float for Solids= media type="custom" key="24119184"

Key Concepts

 * The density of an object determines whether it will float or sink in another substance
 * An object will float if it is less dense than the liquid it is placed in
 * An object will sink if it is more dense than the liquid it is placed in

Objective
Students will be able to determine whether an object will sink or float by its density to the density of water

Materials Needed

 * 2 tea light candles in their metal containers
 * clay
 * water in cup
 * small balance
 * tape
 * dropper

Wax is made of carbon hydrogen atoms connected together in long chains.
 * 1) Watch the demonstration.
 * 2) Complete the activity on your sheet and record your observations.

Even though they both have logs of hydrogen atoms, water is more dense than wax because the oxygen in water is heavier and smaller than the carbon in the wax.

Clay has oxygen atoms like water, but it also has heavier atoms like silicon and aluminum.

3. Complete the //Take It Further// section of your activity sheet 4. Complete the Film Canister project.

=Chapter 3, Lesson 5: Density: Sink and Float for Liquids= media type="custom" key="24119574"

Key Concepts

 * Since density is a characteristic property of a substance, each liquid has its own characteristic density
 * The density of a liquid determines whether it will float on or sink in another liquid
 * A liquid will float if it is less dense than the liquid it is placed in
 * A liquid will sink if it is more dense than the liquid it is placed in

Objective
Students will be able to determine whether a liquid will sink or float in water by comparing its density to the density of water

Materials Needed

 * balance
 * isopropyl alcohol, 91%
 * water
 * graduated cylinder
 * 2 tall clear plastic cups (identical)
 * 2 tea light candles
 * vegetable oil
 * food coloring
 * tall clear plastic cup
 * carrot slice about 1/4-inch thick
 * salt
 * spoon


 * 1) Watch the demonstration that shows different liquids have different densities. Answer the questions on your activity sheet.
 * 2) Complete the procedure on your activity sheet and record your observations (//note, add a drop of food coloring to your water and a different color to the alcohol so the liquids are more visible)//
 * 3) [[image:ahomeschool/oil.jpg]] Molecules of oil are mostly made of carbon and hydrogen atoms bonded together
 * 4) [[image:ahomeschool/water.jpg]] Water molecules are made up of oxygen and hydrogen atoms bonded together
 * 5) [[image:alcohol.jpg]]Alcohol molecules are mostly carbon and hydrogen atoms so they are similar to oil.
 * 6) Complete the //Take It Further// section by performing the following experiment. Record your observations on your activity sheet.
 * Pour water into a clear tall plastic cup until it is about 1/2-filled
 * Place a slice of carrot in the water.
 * Now add about 1 tsp of salt to the water and stir. Continue to stir until the carrot floats to the surface of the salt water. If the carrot does not float to the surface, add more salt and stir.

=Chapter 3, Lesson 6: Temperature Affects Density= media type="custom" key="24126468"

Key Concepts

 * Heating a substance causes molecules to sped up and spread slightly further apart, occupying a larger volume that results in a decrease of density
 * Cooling a substance causes molecules to slow down and get slightly closer together, occupying a smaller volume that results in an increase in density
 * Hot water is less dense and will float on room-temperature water
 * Cold water is more dense and will sink in room-temperature water

Objective
Students will be able to explain, on the molecular level, how heating and cooling affect the density of water

Materials Needed

 * Cold water (colored blue) in foam cup
 * Hot water (colored yellow) in foam cup
 * Room temperature water in clear plastic cup
 * 2 droppers
 * 2 identical clear baby food jars
 * water-resistant card
 * paper towels
 * ice
 * food coloring
 * sheet of plain white paper

In Chapter 3, you saw that different substances have different densities. In today's activity, you will see that the //same// substance can have //different// densities at different temperatures.
 * 1) Make a prediction (write your answer at the top of your activity sheet): Do you think hot and cold water will mix together or stay separate? Watch the demonstration to find out.
 * 2) media type="file" key="density_hot_cold.wmv" width="300" height="300"
 * 3) Record your observations on your activity sheet
 * 4) Complete the experiment from your activity sheet. Record your observations.
 * 5) media type="file" key="hot_cold_water.swf" width="360" height="270"Watch this animation and answer the questions on your activity sheet.
 * 6) Complete the //Take It Further// activity on your worksheet
 * 7) Read Chapter 3 - Student Reading