Warm UpWarm Up

.095 Km = ____ dm.095 Km = ____ dm 0.50 mg = _____ g0.50 mg = _____ g 23 L = ______mL23 L = ______mL 62.5 decameter= _____cm62.5 decameter= _____cm 325m = _______Km325m = _______Km 297 g = ________Kg297 g = ________Kg

Mass, Weight and Mass, Weight and DensityDensity

Developed by the French in the late 1700’s. Developed by the French in the late 1700’s. Based on powers of ten, so it is very easy Based on powers of ten, so it is very easy

to use.to use. Used by almost every country in the world, Used by almost every country in the world,

with the notable exception of the USA.with the notable exception of the USA. Especially used by scientists.Especially used by scientists. Abbreviated SI, which is French for Systeme Abbreviated SI, which is French for Systeme

International.International.

Metric SystemMetric System

Mass is a measure of the amount of substance in a body.

SI Unit: Kilogram (kg) Large masses are measured in tons while

small masses are measured in grams.

MASSMASS

We will use a double beam balanceWe will use a double beam balance

Measuring MassMeasuring Mass

Gravitational force acting on an objectGravitational force acting on an object

W = mgW = mg

where m is the mass of the objectwhere m is the mass of the object

g is the gravitational field strength.g is the gravitational field strength.

Weight is measured in newtons (N)Weight is measured in newtons (N)

Weight is . . .Weight is . . .

The gravitational field is a region in The gravitational field is a region in which a mass experiences a force due which a mass experiences a force due to gravitational attraction. to gravitational attraction.

Gravitational field strength is Gravitational field strength is gravitational force acting per unit mass gravitational force acting per unit mass on an object. on an object.

On earth, the gravitational field On earth, the gravitational field strength is strength is

9.5 m/s2.9.5 m/s2.

Gravitational Field StrengthGravitational Field Strength

Volume is the amount of space an Volume is the amount of space an object consumes. object consumes.

The base unit for volume is the liter. The base unit for volume is the liter. There are two methods for finding There are two methods for finding

volume.volume.

VolumeVolume

We can find the volume of box shapes with We can find the volume of box shapes with the formula Volume = length x width x the formula Volume = length x width x height.height.

In this case the units would be cubic In this case the units would be cubic centimeters (cm3).centimeters (cm3).

So a box 2 cm x 3 cm x 5cm would have a So a box 2 cm x 3 cm x 5cm would have a volume of 30 cm3 volume of 30 cm3 2 cm

5 cm

3 cm

Volume of Regular ObjectsVolume of Regular Objects

We measure volume of irregular objects with a graduated cylinder.

This method is called water displacement

Liquids form a curved surface in graduated cylinders.

Take your reading at the low point of the curve or MENISCUS

Water Displacement

Pour 7 ml of water in a graduated cylinder. If a rock causes the level to rise to 9 ml, the rock must have a volume of 2 ml.

Weight is measured using a balance Weight is measured using a balance such as thesuch as the

spring balancespring balance compression balancecompression balance

Measurement InstrumentsMeasurement Instruments

Differences between Weight and Differences between Weight and MassMass

Weight Mass

pull of gravity on the body amount of matter in the body

DENSITYDENSITY

Q) Which weighs more:-Q) Which weighs more:-A kilogram of feathers or a kilogram of A kilogram of feathers or a kilogram of

iron?iron?

What is Density?What is Density?

Density is the Mass per unit Volume

Wood Water Iron

1 cm3 1 cm3 1 cm3

If you take the same volume of different substances, then they will weigh different

amounts.

0.50 g 1.00 g 8.00 g

Q) Which has the greatest mass and therefore the most dense?

IRON

Density = MassVolume

g or kg

cm3

gcm-3 or kgm-3

Density Equation:

DENSITY OF A REGULAR SOLIDDENSITY OF A REGULAR SOLID

Find the Mass Find the Mass of the solid on of the solid on a balance.a balance.

Measure the Measure the three lengths three lengths and calculate and calculate the Volume.the Volume.

(ie V = l x w x h )(ie V = l x w x h ) Calculate the Calculate the

Density.Density.4.0 cm

2.0 cm

3.0 cm

= m = 240 =10.0 g/cm3

V 24

m = 240 g

Density Formula Wheel

• Formula wheels make it easy to solve density problems.

• Cover the property you are trying to find, and do what is left over.

• To find density, cover the word density. You have mass over volume remaining. So divide mass by volume to find density

Density Volume

DENSITY OF AN IRREGULAR SOLIDDENSITY OF AN IRREGULAR SOLID

Find the Mass of the Find the Mass of the solid on a balance.solid on a balance.Fill the Measuring Fill the Measuring Cylinder with Water to a Cylinder with Water to a known Volume.known Volume. Add the Object.Add the Object. Work out the Volume Work out the Volume of Water that is of Water that is displaced.displaced. Calculate the Density.Calculate the Density.

50 cm3

80 cm3

m = 360 g = m = 360 =12.0 g/cm3

V 30

Now You TryNow You Try

You have a rock with a volume of You have a rock with a volume of 15cm15cm33 and a mass of 45 g. What is and a mass of 45 g. What is its density?its density?

You have a different rock with a You have a different rock with a volume of 30cmvolume of 30cm33 and a mass of 60g. and a mass of 60g. What is its density? What is its density?

In the above two examples which In the above two examples which rock has the greater density?rock has the greater density?

Now You TryNow You Try

You decide you want to carry a You decide you want to carry a boulder home from the beach. It is boulder home from the beach. It is 30 centimeters on each side, and so 30 centimeters on each side, and so has a volume of 27,000 cmhas a volume of 27,000 cm33. It is . It is made of granite, which has a typical made of granite, which has a typical density of 2.8 g/cmdensity of 2.8 g/cm33. How much will . How much will this boulder weigh? this boulder weigh?

Now You TryNow You Try

A golden-colored cube is handed to you. A golden-colored cube is handed to you. The person wants you to buy it for The person wants you to buy it for $100, saying that is a gold nugget. You $100, saying that is a gold nugget. You pull out your old geology text and look pull out your old geology text and look up gold in the mineral table, and read up gold in the mineral table, and read that its density is 19.3 g/cmthat its density is 19.3 g/cm33. You . You measure the cube and find that it is 2 measure the cube and find that it is 2 cm on each side, and weighs 40 g. cm on each side, and weighs 40 g. What is its density? Is it gold? Should What is its density? Is it gold? Should you buy it? you buy it?

DENSITY OF AN IRREGULAR SOLIDDENSITY OF AN IRREGULAR SOLID

OR use a Eureka Can to find the Volume.OR use a Eureka Can to find the Volume.

Find the mass of the solid Find the mass of the solid on a balance.on a balance.Add water until just Add water until just overflowing.overflowing. Place a Measuring Cylinder Place a Measuring Cylinder under the spout.under the spout. Add the Object.Add the Object. Collect the Water and read Collect the Water and read off the Volume.off the Volume.Calculate DensityCalculate Density

m = 440 g

40.0 cm3

= m = 440 =11.0 g/cm3 V 40

DENSITY OF A LIQUIDDENSITY OF A LIQUID

Find the Mass of an empty Find the Mass of an empty Measuring Cylinder.Measuring Cylinder.

Add a certain Volume of Add a certain Volume of Liquid.Liquid.

Find the Mass of the Find the Mass of the Measuring Cylinder and Measuring Cylinder and LiquidLiquid

Calculate the Mass of Liquid.Calculate the Mass of Liquid. How?How? Calculate Density of Liquid.Calculate Density of Liquid.

25.0 g

20.0 cm3

45.0 g

45 – 25 = 20 g = m = 20 =1.00 g/cm3 V 20

Mass of Liquid = Mass of Measuring Cylinder and Liquid – Mass of empty Measuring Cylinder