Learning Goals

Explain the meaning of mass and describe the units for measuring mass.

Distinguish between mass and weight.

Define volume and explain how the volume of matter is measured.

Key Question: How do you measure mass and volume?

Measuring Mass and Volume

Measuring massMass describes the

amount of matter in an object.

The SI unit for mass is the kilogram (kg).

The kilogram is too large a unit to be convenient for small masses.

One gram (g) is one-thousandth of a kilogram.What is the estimated mass of ONE zinc nut?

MatterMatter is anything

that has mass and takes up space.

All matter has mass.

Steel, plastic, rubber, and glass are different kinds of matter.

A car has a lot more of each kind of matter than a bike.

Mass and weight are different We tend to use the terms mass

and weight interchangeably, but they are not the same thing.

Mass is the amount of matter in an object.

Weight is a measure of the pulling force of gravity on an object.

Mass and weight are different A 2.3 kg bag of

flour has a mass of 2.3 kilograms no matter where it is in the universe.

The weight of the bag of flour is less on the moon.

The 5 lb bag of flour on Earth weighs only .8 lbs on the moon!

VolumeVolume is the amount of space an

object takes up.

The fundamental unit of volume in SI is the cubic meter (m3).

More convenient smaller units are cubic centimeters (cc or cm3), liters (L) and milliliters (mL).

VolumeMeasuring the volume of liquids is easy.

Pour the liquid into a graduated cylinder and read the meniscus at eye level.

DisplacementYou can find the

volume of an irregular shape using a technique called displacement.

Put the irregularly shaped object in water and measuring the amount of water displaced.

Comparing mass and volumeMass and volume are

two different properties of matter.

Size does not always indicate an object’s mass!

How the matter is packed into space is more important.

Learning Goals

Define density in terms of mass and volume.

Identify units used to express the density of materials.

Apply the density formula to solve problems.

Key Question: How is an object’s density

related to its volume, mass, and tendency to sink or float?

Density

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

Density

Solids, liquids and gases are matter, so they all have density.

The density of water is about one gram per cubic centimeter.

DensityThe 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 of common materialsDensity 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

(“sodder)

2.2 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.

Determining Density To find the density of a

material, you need to know the mass and volume of a solid sample of the material.

1. Mass is measured with a balance or scale.

2. Use the displacement method or calculate the volume.

DensityDensity changes for different substances

because:1. Atoms have different masses.2. Atoms may be “packed” tightly or loosely.

Calculating Density1. Looking for: …the density of the candle

2. Given: …mass = 1500 g; volume = 1700 mL

3. Relationship: D = m/V

# Sig. fig = .88 g/mL

Solving Problems

4. Solution: 1,500 g ÷ 1,700 mL = 0.8823529 g/mL