Applying tools - density and buoyancy
Essential Understanding
Mixtures are made of combinations of elements and/or compounds, and they can be separated by using a variety of physical means including by density, buoyancy and specific gravity.
Essential Questions
How can we apply our knowledge of tools to get information?
How can density, a physical property of matter, be used to identify elements or mixtures?
Why do elements or mixtures sink or float (buoyancy)?
Does the density of an element or mixture change due to the amount or temperature of the substance?
What are the similarities and difference among density, buoyancy and specific gravity?
Lesson Objectives
1. Distinguish between mass and density.
2. Explain that density is a ratio of mass to volume (Density = mass/volume).
3. Use density to identify elements or mixtures.
4. Demonstrate that different substances float or sink in depending on their density.
5. Conduct and report on an investigation that uses physical means such as density to separate substances in a mixture.
Key Concepts
PowerPoint Presentations
Things I Need to Remember/Know from Chemistry
Finding Density - Lesson 1: What is density and how is it calculated?
Finding Density - Lesson 2: Finding volume and density via liquid displacement (Archimedes' Principle)
Density of Liquids - Lesson 3
Buoyancy and Specific Gravity
Class Assignments
Density - Student Reading Packet
Volume of Cylinders
Volume of Prisms (rectangles and squares)
Density Lab 1 - What is Density? Identifying elements and mixtures using cubes that have the same volume but different mass.
Density Lab 1 - answer key
Density Lab 2 - Finding volume (and density) via liquid displacement (6th Grade)
Density Lab 2 - answer key
Density Lab 2B - Liquid displacement method versus direct measurement method (7th and 8th Grade)
Density Lab 3 - Density of Liquids
Density Lab 3 - answer key
Density Lab 4 - Buoyancy part 1
Density Lab 4 - Buoyancy part 2
Links for Media Used in Class
Archimedes Principle youtube
Archimedes Principle by science kids
Other Helpful Resources
Buoyancy Video - Bill Nye the Guy
Google Science Fair 2014
Specific Gravity of Liquids and Fluids - by the Engineering Toolbox
Determining the Quality of Honey using specific gravity
How Stuff Works - Buoyancy
Lab Safety and Equipment
Mixtures are made of combinations of elements and/or compounds, and they can be separated by using a variety of physical means including by density, buoyancy and specific gravity.
Essential Questions
How can we apply our knowledge of tools to get information?
How can density, a physical property of matter, be used to identify elements or mixtures?
Why do elements or mixtures sink or float (buoyancy)?
Does the density of an element or mixture change due to the amount or temperature of the substance?
What are the similarities and difference among density, buoyancy and specific gravity?
Lesson Objectives
1. Distinguish between mass and density.
2. Explain that density is a ratio of mass to volume (Density = mass/volume).
3. Use density to identify elements or mixtures.
4. Demonstrate that different substances float or sink in depending on their density.
5. Conduct and report on an investigation that uses physical means such as density to separate substances in a mixture.
Key Concepts
- Density is a characteristic property of a substance.
- The mass of atoms, their size, and how they are arranged determine the density of a substance. Even though an atom may be smaller than another atom, it might have more mass.
- Density equals the mass of the substance divided by its volume; D = m/v.
- 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 (1cm3).
- Just like solids, liquids also have their own characteristic density.
- The volume of a liquid can be measured directly with a graduated cylinder.
- 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 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.
- Heating a substance causes molecules to speed up and spread slightly further apart, occupying a larger volume that results in a decrease in 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.
PowerPoint Presentations
Things I Need to Remember/Know from Chemistry
Finding Density - Lesson 1: What is density and how is it calculated?
Finding Density - Lesson 2: Finding volume and density via liquid displacement (Archimedes' Principle)
Density of Liquids - Lesson 3
Buoyancy and Specific Gravity
Class Assignments
Density - Student Reading Packet
Volume of Cylinders
Volume of Prisms (rectangles and squares)
Density Lab 1 - What is Density? Identifying elements and mixtures using cubes that have the same volume but different mass.
Density Lab 1 - answer key
Density Lab 2 - Finding volume (and density) via liquid displacement (6th Grade)
Density Lab 2 - answer key
Density Lab 2B - Liquid displacement method versus direct measurement method (7th and 8th Grade)
Density Lab 3 - Density of Liquids
Density Lab 3 - answer key
Density Lab 4 - Buoyancy part 1
Density Lab 4 - Buoyancy part 2
Links for Media Used in Class
Archimedes Principle youtube
Archimedes Principle by science kids
Other Helpful Resources
Buoyancy Video - Bill Nye the Guy
Google Science Fair 2014
Specific Gravity of Liquids and Fluids - by the Engineering Toolbox
Determining the Quality of Honey using specific gravity
How Stuff Works - Buoyancy
Lab Safety and Equipment