The Nature of Science and Technology

Chapter 2 – Section 1

• Measurement – A Common Language– A Standard Measurement System

• Metric System• International System of Units (SI)

– Length• Units of Length• Measuring Length

– Mass• Units of Mass• Measuring Mass• Difference Between Mass and Weight

– Volume• Volume of Liquids, Solids, Irregular Solids

– Density• Units of Density• Densities of Common Substances

– Time• Units of Time• Measuring Time

– Temperature• Units of Temperature• Measuring Temperature

Key Concepts

• Why do scientists use a standard measurement system?

• What are the SI Units of measure for length, mass, volume, density, time, and temperature?

• How are conversion factors useful?

Standard Measurement System

• Metric System– Developed in France (1790s)– Universal system called the Metric System– System of Measurement based on the

number 10

Standard Measurement System

• International System of Units (SI)– Version of metric system used by modern

scientists– Scientists use SI units to measure length,

volume, mass, density, temperature, and time– Standard system of measurement allows

scientists to compare data and communicate with each other about their results

SI Units

• Based on multiples of 10

• Each unit is 10 times larger than the next smallest unit and one tenth (1/10) the size of the next largest unit

• Refer to Figure 1 – Pg 45

Length

• Units of Length– Distance from one point to another– The basic unit of length in the SI system is

the meter (m).– To measure smaller objects, use centimeter

(cm) or millimeter (mm)

Length

• Measuring Length– Tools – Metric ruler

• Centimeter markings

Mass

• Mass is a measure of the amount of matter an object contains.

• Units of Mass– The basic unit of mass in the SI system is

the kilogram (kg).– To measure the mass of smaller objects, use

gram (g) as the unit

Mass

• Measuring Mass– Balance

• Triple Beam Balance– Appendix C for directions

Mass

• Difference Between Mass and Weight

• Weight is a measure of the force of gravity acting on an object

• Mass is a measure of the amount of matter an object contains.

• Weight is a measure of the force of gravity acting on an object

Learning Check

• What is the basic unit of length in the SI system?

• What is mass?

• What is the basic unit of mass in the SI system?

Volume

• Volume is the amount of space an object takes up.

• Volume of Liquids– To measure the volume of a liquid, use a unit

known as the liter (L)– For smaller volumes use milliliters (mL)

Volume

• Volume of Rectangular Solids– Volume of a solid object, use cubic centimeter

(cm3)– For solids with larger volumes, scientists

use the SI unit known as the cubic meter (m3)

– Volume = Length x Width x Height– Example: 20cm x 6cm x 25cm = 3000 cm3

Volume

• To calculate volume… (pg 50 and 51)– Multiply the numbers– Multiply the units– ***Make sure you use the same units for all

measurements when calculating the volume of a regular solid***

Volume

• Volume of Irregular Solids

• Can you measure length? Width? Or Height???

• Instead… try immersing the object in water– Water level will rise– Displacement of volume can be determined

Vocabulary: Meniscus

• The curved upper surface of a liquid in a column of liquid

• Draw picture

Density

• The measure of how much mass is contained in a given volume

• Density = Mass/Volume

Density

• Units of Density– Density is made up of two other

measurements • Mass• Volume

– An object’s density is expressed as a combination of two units.

– Example: grams per cubic centimeter– Example: grams per milliliter (g/mL)

Densities of Common Substances

• Figure 6 – Pg 53

Time

• Units of Time

• The second (s) is the SI unit used to measure time.

Time

• Measuring Time– Clocks– Watches

• Look at conversions for time (pg 53)

Temperature

• Units of Temperature (pg 54)– Celsius temperature scale– Water freezes at 0 degrees Celsius– Water boils at 100 degrees Celsius– Human body temperature is 37 degrees

Celcius

– Kelvin scale (K) is the official SI unit for temperature

Temperature

• Measuring Temperature– Thermometer

Converting Between Units

• Need to know conversion factor

• A conversion factor is an equation that shows how two units of measurement are related

Converting Between Units (pg 55)

• Write down the measurement you want to convert

• Find conversion factor that relates the two units you are converting

• Write conversion factor as a fraction (include units)

• Multiply the measurement you are converting from by the fraction– Units will cancel out with the units in the denominator

of fraction

Chapter 2: Section 2

Mathematics and Science

Estimation

• An estimation is an approximation of a number based on reasonable assumptions

• Scientists rely on estimates when they cannot obtain exact numbers

• Not the same as guessing because an estimate is based on known information!

Accuracy

• Refers to how close a measurement is to the true or accepted value

Precision

• Refers to how close a group of measurements are to each other

Accuracy and Precision in Measurements

• Both accuracy and precision are important when you make measurements

• See Figure 11 – pg 62

Significant Figures

• The digits included in a measurement

• Include all of the digits that have been measured exactly, plus one digit whose value has been estimated

Significant Figures

• Adding and Subtracting– The answer can only have as many figures

after the decimal point as the measurement with the fewest figures after the decimal

Percent Error

• Percent error calculations are used to determine how accurate, or close to the true value, an experimental value really is

• Percent error = Difference between experimental value and true value/True value x 100%

• A low percent error means that the result you obtained was very accurate

• A high percent error means that your result was not very accurate

Mean, Median, and Mode

• Mean – Add up all numbers and divide by the number of data added up

• Median – Middle number in a row of numbers (lowest to highest)

• Mode – Numbers that appears the most in a given set of data