Density

Key Questions What is density? How is density measured? How do you calculate density? In this Investigation, students will explore the property of density in liquids. They will construct a density column, and then use the column to predict the density of a solid.

Density is the measure of the “compactness” of a material How close the atoms or molecules are to each other More than “heaviness” - density includes how much space an object takes up!! All substances have density including liquids, solids, and gases Bread slice and compacted bread in large flask of water

“Compactness” Hot air balloon - Describe how a hot air balloon works. Defend your argument.

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

Mass is amount of matter in an object (usually measured in grams) Volume is the amount of space an object takes up (usually measured in ml or cm3)

We have a kilogram of feathers and a kilogram of steel… We have a kilogram of feathers and a kilogram of steel… which has more mass? Which has a larger volume? Which is more dense? OR ROCKS - pass around

Density = mass/volume or D= m/v Density EQUATION Density = mass/volume or D= m/v A solid wax candle has a volume of 1,700 mL. The candle has a mass of 1.5 kg (1,500 g). What is the density of the candle?

…the density of the candle Given: …mass = 1500 g; volume = 1700 mL Solving Problems Calculating Density Looking for: …the density of the candle Given: …mass = 1500 g; volume = 1700 mL Relationship: D = m/V Solution: 1,500 g ÷ 1,700 mL = 0.8823529 g/mL = .88 g/mL

What do you think? If the volume stays the same and the mass increases . . . the density will If the mass stays the same and the volume increases . . . The density will increase decrease

Lead floats on liquid mercury! Explain.

Density Solids, liquids and gases are matter, so they all have density. The density of water is about one gram per cubic centimeter.

Density The units used for density depend on whether the substance is solid or liquid. For liquids use units of grams per milliliter (g/mL) For solids use density in units of g/cm3 or kg/m3.

Density Density is a property of material independent of quantity or shape.

Density of common materials Liquids tend to be less dense than solids of the same material. Ex. solder

Density of common materials Water is an exception to this rule. The density of solid water (ice) is less than the density of liquid water.

Density of common materials Ice vs. water…..

Determining Density To find the density of a material, you need to know the mass and volume of a solid sample of the material. Mass is measured with a balance or scale. Use the displacement method or calculate the volume.

DETERMINING DENSITY Use a graduated cylinder Regular Shapes – mass, then determine the volume by formula EX: cubes, cylinders, spheres, cones, etc. Irregular shapes – mass, then measure displacement of a liquid (usually water) by that irregularly shaped object Use a graduated cylinder Add water to a predetermined level - record. Gently drop in the irregularly shaped object. Read the graduated cylinder – record. Subtract the first water level from the second – this is the volume

Density Table SINK or FLOAT In Water (D = 1.0 g/mL) Float Float Float (alcohol) Float (fuel)