Notes – Density Chapter 3 Lesson 1

Density  Which would have more mass?  It depends on BOTH the size of the object AND the material contained inside.

Density  Density is the amount of mass per unit volume of a material.  Matter is made of atoms which are particles that have mass.  Density depends on mass AND the number of particles packed into a given volume.

Density  The volume of air has fewer particles, thus less mass than the same volume of water.  Thus, the density of air is less than the density of water. <

Density D = m V D – density, the unit is g / cm 3 (solids) or g / mL (liquids) m – mass, the unit is g V – volume, the unit is cm 3 (solids) or mL (liquids)

Density  Density depends on the material an object is made from, NOT its size.  An entire chocolate bar will have the same density as just one piece. It’s all made from the same material – chocolate.

Density  Density depends on the mass of the particles. (more mass = more density)  Density depends on the distance between particles. (more distance = less density)  Gases are usually less dense than solids or liquids because particles are far apart.

Density

Density

Density  To make something less dense, you can decrease the mass or increase the volume of an object.  A solid steel ball sinks in water, but that same mass of steel made into a curved hull of a boat will float – the shape of the hull causes it to displace a greater volume of water than a solid ball.

Measuring Density 1. Measure its mass. 2. Measure its volume. 3. Divide its mass by its volume.

Measuring Mass  For a solid, place it directly on the balance.  For a liquid: 1. Measure the empty container. 2. Measure the container AND liquid. 3. Subtract the container from the total mass.

Measuring Volume  For a liquid, use a graduated cylinder.

Measuring Volume  For a rectangular solid (all sides are rectangles): 1. Measure its length, width, height. 2. Multiply all 3 numbers together.

Measuring Volume  For an irregular solid, you have to use the “displacement” method: 1. Record the volume of water in a graduated cylinder. 2. Place the object CAREFULLY (without splashing) into the graduated cylinder, and record the new volume. 3. Subtract the volume of the water from the combined volume. Then you know the volume of just the object.

Density is a Physical Property  A physical property is something you can measure without changing the composition of the material.  When you measure an object’s mass and volume, you don’t change it into something else.

Density equals ____ divided by volume. Aforce Bmatter Csolid Dmass 3.1 Density

Density ____ as the distance between particles in an object ____. Aincreases; decreases Bincreases; increases Cdecreases; decreases Dnone of the above 3.1 Density

Calculate the volume of a rock that has a mass of 12 g and a density of 3 g/cm 3. A9 cm 3 B15 cm 3 C4 cm 3 D4 cm 3.1 Density