Lesson 35 - What is Density? Density and Fluids What Affects Density? How to Calculate Density?

The Big Idea!!! Density is a measure of how many particles, and how much mass is packed into a specific volume!

Readings Use pages 50 - 57 in the Science Focus 8 Textbook to help you complete the worksheet. Use pages 42 - 49 in the Science in Action 8 Textbook to help you complete the worksheet.

What is Density? Density is the measurement of the amount of matter in a given area Density is the description of the “crowdedness” of the particles that make up matter Explain this picture… how can she float so easily?

What is Density? The density of a substance is related to its physical properties Remember that all matter is made up of tiny particles and that different matter consists of different types of particles Well, the particles of one substance may interact differently than another causing them to be closer together, heavier, or stronger attractions, all which cause the substance to be more dense

Properties of Density Walking through water is harder than walking through air This is because the density of the water is greater than that of air The particles are more closely packed together and they have stronger attractive forces to break

Properties of Density Generally we say that gases are less dense than liquids, and liquids are less dense than solids This is because the particles are generally packed together tighter in solids than they are in liquids or gasses Is this always true all of the time?

Properties of Density Sometimes we find that solids are less dense than liquids Look at the examples below

Properties of Density In these cases, the particles of the fluids are more dense than the solids they support

Density Diagram Below are two volumes of equal size and capacity filled with the same type of particle Which one is more dense? How do you know?

Density Diagram The box on the right is denser because it is heavier More particles (of the same substance) = more mass = more dense

Density Diagram If the particles on the left weigh 4 times more than the particles on the right, which box is more dense now?

Density Diagram Blue particles are 4 times heavier than red particles 8 blue particles means you would have to have 32 red particles to be equal (8 x 4 = 32) But there are only 24 red particles so the box on the left has more mass meaning it’s more dense

Density Diagram If these two different substances were liquids and they were mixed, which would settle out on the bottom and which would settle out on the top?

Density Diagram If these two fluids were mixed then the heavier substance (blue particles) would settle out on the bottom

Fluids on Fluids Because the particles making up the oil are less dense than the water particles, the oil settles out on top of the water Lets look at this example with a few more different density liquids like: Soap, oil, & water

Changing Density Just like with diffusion and viscosity, the one factor that can change density is TEMPERATURE Temperature can affect the density of a substance by causing the particles to move faster and further apart By expanding the space between the particles, you are increasing the volume which affects density

Density vs. Temperature Lets look at the Density Thermometer… What is happening to the density of the water particles within the thermometer as it is cooled? What is happening to the density of the water particles within the thermometer as they being to warm back up?

Changing Density Just like in a hot air balloon, we heat the air which causes the particles to expand and spread apart until it becomes less dense than the cold air The change in density can be great enough that the balloon will become less dense even with the basket and passengers

Your Assignment You are being handed a short worksheet that deals with Density Use your notes to answer the questions that on the worksheet