Measuring density Thursday 9/17/09. What density is and how to measure it What we will learn…

Measuring density

Thursday 9/17/09

•What density is and how to measure it

What we will learn…

•PowerPoint and video

•Notes

•Worksheet

•Lab (only if you complete the worksheet)

How we will learn it…

From Tuesday

Ruler: http://www.k12math.com/math-concepts/measurement/ruler-cm.jpg

Mass: the amount of matter in an object

Metric System: Mass

1 milligram is like a few grains of salt1 gram is like a paper clip1 kilogram is like a textbook

1 gram (g) = 1000 milligram (mg)

1 kilogram (kg)= 1000 gram (g)

From Yesterday

Metric System: Length

Base unit is the meter “m”

1 centimeter is as big as the tip of your pinky

1 millimeter is as big as a dime on its edge

1 meter (m)= 100 centimeters (cm)

1 meter (m)= 1000 millimeters (mm)

1 centimeter (cm)= 10 millimeters (mm)

1 kilometer (km) 100 meters (m)

From Wednesday

Ruler: http://www.k12math.com/math-concepts/measurement/ruler-cm.jpg

Volume: the amount of space something takes up

The base unit of volume is the liter “L” or “l”.

Standard: 1 liter is equal to one cubic decimeter

Metric System: Volume

1 liter (l)= _____ milliliter (ml)

From Thursday

Ruler: http://www.k12math.com/math-concepts/measurement/ruler-cm.jpg

Mass: the amount of matter in an object

Base unit is the kilogram “kg”

1 milligram is like a few grains of _______1 gram is like a _________1 kilogram is like a ________________

1 gram (g) = _____ milligram (mg)

1 kilogram (kg)= _____ gram (g)

Density is defined as mass per unit volume. It is a measure of how tightly packed and how heavy the molecules are in an object. Density is the amount of matter within a certain volume.

Which do you think would have the greater density?

Why?• 1 kg of feathers • 1 kg of rock

Proof that water and ice have different densities

To find the density1- Find the mass of

the object

2- Find the volume of the object

3- Divide Density = Mass

Volume

1) Find the mass of the object

2) Find the volume of the object

3) Divide : Density = Mass - Volume

To find density:

Ex. If the mass of an object is 35 grams and it takes up 7 cm3 of space, calculate the density.

Set up your density problems like this:

Given: Mass = 35 grams Unknown: Density (g/ cm3) Volume = 7 cm3

Formula: D = M / V Solution: D = 35g/7 cm3

D = 5 g/cm3

Practice Problems

1. A small block of wood floats on water. It has a volume of 25 cubic centimeters and a mass of 20 grams. What is the density of the wood?

M=20 g

V =25 cm

D= 0.8g/cm3

Practice Problems

2. A ample of liquid has a mass of 24 grams and a volume of 16 milliliters. What is the density of the liquid?

M=24 g

V =16 cm

D= 1.5 g/ml3

Practice Problems

3. A metal sample has a mass of 43.5 grams and a volume of 15 cubic centimeters. What is its density?

M=43.5 g

V =15 cm

D= 2.9 g/cm3

Another Way of Looking at It

You will often hear density referred to as“mass per unit volume.”• Mass is how much matter the object has.• Per simply means divided by• Unit volume is a measure of how muchspace it takes up

When you hear mass per unit volume, you should think…• Take the mass and divide by its volume!

Notes on Density

•Density is the measure of how much mass is contained in a given volume.•Density = Mass /Volume (mass divided by volume)•Solids -- g/cm3

•Liquids -- g/ml (1 ml is 1 cm3)•Density of water is 1.00 g/ml3