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Part 1: Accuracy & Precision Draw two bullseyes. On one, show three darts that are accurate. On the other, show three darts that are precise.
Part 2: Error & Percent ErrorA thermometer in boiling water reads 99.1°C. Calculate the error and the percent error.
YWBAT
• Explain why metric units are easy to use.
• Identify the temperature units scientists usually use.
• Calculate the density of a substance.
Measuring Length
• What units can you use to report length?
Measuring Length
• What units can you use to report length?
– Inches
– Feet
– Meters
– Miles
Metric Units
• The standards of measurement used in science are those of the metric system
• All metric units are based on multiples of 10.
• This makes it easy to convert between units
SI Units
• The metric system was established in France in 1795
• The International System of Units is a revised version of the metric system. It is abbreviated SI after the French name, Le Système International d’Unités.
• The SI was adopted by international agreement in 1960.
SI Units
• There are 7 base SI units
• From these base units, all other SI units of measurement can be derived.
• Derived units are used for measurements such as volume, density, and pressure.
Units of Length
• In SI, the basic unit of length is the meter (m).
• All measurements of length can be expressed in meters.
• For very large and very small lengths, however it may be more convenient to use a unit of length that has a prefix.
Unit Prefixes
Units of Length
• The SI unit for length is a meter (m).
• The prefix milli- means 1/1000• 1 millimeter = 1/1000 of a meter = 0.001m• 1 mm = 0.001m
• The prefix kilo means 1000 times larger• 1 kilometer = 1000 meters• 1 km = 1000m
Funny Forms of 1
Units of Volume
• Volume – space occupied by matter
• For a rectangular solid, V = L x W x H
• The SI unit of volume is a cubic meter (m3).
• A more convenient unit of volume for everyday use is the liter, a non-SI unit.
Units of Volume
• A more convenient unit of volume for everyday use is the liter. This is a non-SI unit.
• A liter (L) is the volume of a cube that that is 10 centimeters along each edge.
10cm x 10cm x 10cm = 1000 cm3 = 1L
Units of Volume
• A smaller non-SI unit of volume is the milliliter (mL).
Question?How many cm3 are equivalent to 1 mL?
Units of Volume
• A smaller non-SI unit of volume is the milliliter (mL).
Question?How many cm3 are equivalent to 1 mL? 1 cm3 = 1 mLThe units mL and cm3 are used interchangeably
Measuring Volume
Measuring Volume
Measuring Volume
1. Put on goggles & apron.2. Get the following equipment for each group.
– 100 mL Graduated cylinder– 100 mL Beaker
3. Fill beaker with ~ 70 mL water.4. Pour water into graduated cylinder.5. Read the volume on the graduated cylinder. Be sure
to: – get your eye level at the interface.– read the bottom of the meniscus.
Units of Mass
• Mass – a measure of the quantity of matter.
• The SI unit of mass is the kilogram (kg).
• 1 kg = the mass of 1 L of liquid water at 4°C
• A more convenient unit of volume for everyday use is the gram (g)
• 1 kg = 1000 grams.
Measuring Mass
Weight
1. Zero your balance
2. Determine the tare weight of your beaker
3. Add ~70mL water to your beaker
4. Weigh the beaker containing the water
5. Calculate the weight of the water.
Weight
• Weight is a force that measures the pull on a given mass by gravity.
• The weight of an object can change with its location
Weight
How much would you weigh on the Moon?
Divide your weight on Earth by 6.
Density
• Density is the ratio of the mass of an object to its volume.
• The relationship between an objects mass and volume tells you whether it will float or sink.
• Density is an intensive property.
Density
• The SI unit of density is kilograms per cubic meter (kg/m3).
10 g
0.53 g/cm3
19 cm3
10 g
10 cm3
10 g
3.7 cm3
10 g
0.88 cm3
1.0 g/cm3 2.7 g/cm3 11.4 g/cm3
Increasing density (mass per unit volume)
Density
• Differences in densities cause liquids to separate into layers.
• As shown below, corn oil floats on top of water because it is less dense than water.
Corn oil
Water
Corn syrup
Practice
A copper penny has a mass of 3.1g and a volume
of 0.35 cm3. what is the density of copper?
Practice
A copper penny has a mass of 3.1g and a volume
of 0.35 cm3. what is the density of copper?
Density =31 g
0.35 cm3= 8.8571 g/cm3 = 8.9 g/cm3
Density
• The volume of most substances increase as the temperature increases, while the mass remains the same.
• The density of a substance generally decrease as its temperature increases.
• Water is an important exception.
Temperature
Temperature is a measure of how hot or cold an object is.
•An object’s temperature determines the direction of heat transfer.
•When two objects at different temperature are in contact, heat moves from the object at the higher temperature to the object at the lower temperature.
Temperature
• The SI unit for temperature is the Kelvin, named after Lord Kelvin, a Scottish physicist.
• On the Kelvin scale, the freezing point of water is 273.15 Kelvin (K), and the boiling point is 373.15 K.
* Note that with the Kelvin scale, the degree sign is not used.
Temperature
• Another common unit used to measure temperature is the Celsius scale.
• On the Celsius scale, the freezing point of water is 0°C, and the boiling point is 100°C.
Comparing the °C and K Temperature Scales
* Note - The zero point on the Kelvin scale, 0 K, or absolute 0, is equal to -273.15°C
Comparing the °C and K Temperature Scales
• One degree on the Celsius scale is equivalent to one Kelvin on the Kelvin scale.
• To convert between the temperature scales,
Practice
Normal human body temperature is 37°C. What
is this temperature in kelvins?
Practice
Normal human body temperature is 37°C. What
is this temperature in kelvins?
310 K
Practice
A student is performing an
experiment and measures the
temperature of water to be 350 K.
What is the temperature of the water
in ºC?
Practice
A student is performing an
experiment and measures the
temperature of water to be 350 K.
What is the temperature of the water
in ºC?
77ºC
