Measurement,Units, &

Conversions

SI UNITSALL MEASUREMENTS CONSIST OF A NUMBER AND A UNIT!!!

Good: 6 m, 5 ft, 20 C

Bad: 6, 5, 20

Common Decimal Prefixes

CommonSI to

EnglishUnit

Conversions

Mass is the property of a body that causes it to have weight in a gravitational field.

Mass is constant!!

Mass does not change unless matter is added or removed from an object.

Mass does not change when shape or location is changed.

A car has the same mass in Los Angeles as it has in New York City.

Scientific Definition: Weight is the vertical force exerted by a mass as a result of gravity

Definition: Weight is how heavy something is…how much it weighs.

Weight is not constant!

Weight changes depending on the pull of gravity.

i.e. The farther an object is from the center of the Earth (or the center of the gravitational force), the less weight the object has.

Feels MORE gravity; weighs MORE.

Feels LESS gravity, weighs LESS.

Volume is the 3-D space occupied by matter.

It is difficult to measure the densities of odd shaped objects. To find their densities, place them in a known amount of water. The amount of water that changes (or is displaced) is the volume.

Measure this water to find the volume of the ball.

Another way to find the volume of a small odd shaped solid is to place it in a known amount of water in a graduated cylinder. The new volume is the volume of the water + the solid. The difference between the volume of the water and the new volume is the volume of the solid. The amount the volume changes is the volume of the solid.

7mL

5mL

The volume of the water is 5mL. The new volume of the water + the solid is 7mL.

7mL – 5mL = 2mL.

The volume of the solid is 2mL.

Density is a measure of mass per unit of volume. The higher an object's density, the higher its mass per volume.

Less dense. More dense.

Scientific Definition: Density is the mass per unit volume of a material.

Definition: Density is how much “stuff” in a given space.

All matter has density, even gas. Density can be used to identify an object.

You can use the formula or a graph to determine density.

Density = rise = massMass run volume

Volume

D = m m = mass D = density V V = volume

Density determines if an object will float or sink in a liquid.

Objects with greater density than the liquid will sink.

Objects with lesser density than the liquid will float.

Temperature is the degree of hotness of a body or environment.

Temperature is the sensation of cold or heat.

Temperature is measured by a thermometer . The units are F, C, or K. We use C or K only.

Convert C to K by adding 273. Convert K to C by subtracting 273.

Intensive PropertiesVs.

Extensive Properties

Extensive Property: a property or measurement that is dependent on the amount of material you have; e.g. mass or volume.

Intensive Property: a property or measurement that is independent of the amount of material you have; i.e. the measurement doesn’t change no matter how much you have; e.g. density.

UNIT CONVERSIONSThe big secret: Numbers with units, like 16.2 meters or 32 ft/sec², are treated exactly the same as coefficients with variables, like 16.2x or 32y/z². You can cancel units the same way you cancel coefficients.

beginning unit x final unit = final unit beginning unit

e.g. convert 5 mi to km.

5 mi x 1.609 km = 8.045 km 1 mi

Try: How many feet in one meter? How many seconds in 12 hours? How many grams in 2 lb? How many C in 291 K?

ExampleCopper can be drawn into thin wires. How many meters of 34-guage wire (diameter = 6.304 x 10-3 in) can be produced from the copper in 5.01 lb of covellite, an ore of copper that is 66% copper by mass? (Hint: Treat the wire as a cylinder: V of a cylinder = πr2h; d of copper = 8.95 g/cm3.

Cu wire diameter = 6.304 10-3 in dCu = 8.95 g/cm3 V = πr2h

Cu = 66% of 5.01 lbmassCu = 5.01 lb 66% = 3.3066 lb 1 Kg = 2.205 lb

3.3066 lb 1 Kg 1000 g = 1499.59 g Cu 2.205 lb 1 Kg

dCu = 8.95g/cm3 = 1449.59 g V = x = 167.55 cm3

x6.304 10-3 in 2.54 cm = 1.601 10-2 cm = diameter 2 = 0.008 cm = radius

1 in167.55 cm3 = 3.1416 0.0082 h h = 8.34 105 cm