Unit A1-3 Plant Science

Conducting Scientific Investigations in Agriculture Problem Area 1 Conducting Scientific Investigations in Agriculture

Using Scientific Measurement Lesson 3 Using Scientific Measurement

Student Learning Objectives 1. Describe the systems of measurement used in our country. 2. Determine the metric prefixes and units used for measuring length, volume, weight, temperature, and area. 3. Understand how to convert numbers within the metric system. 4. Understand how to convert from one system of units to another system of units.

Terms Area Dimensional analysis International System of Units (SI) Length Mass Temperature Volume Weight

What are the types of measurement used in our country? There are two types of measurement used in our country—the English and the metric system. A. Everyday measuring is done using a system of English units. 1. Units such as inch/foot, quart/gallon, and pound/hundred weight are English units. 2. Americans easily understand the English system of measurement because of our familiarity with products measured in inches, gallons, and pounds.

B. In scientific research, the metric system, or International System of Units (SI), is used for measuring length, volume, weight, and temperature. 1. SI is a universal language of measurement for scientists that allows them to share information and be understood everywhere in the world. 2. Units of SI are easier to convert because they are related by powers of ten.

What are the metric prefixes and units used for measuring length, volume, weight, temperature, and area? A. Length is the distance from one point to another. The SI unit of length is the meter. In making measurements, it often is more convenient to report length in terms which signify a portion or combination of meters.

B. Volume is the amount of space a substance occupies and is based on measurements of length (i.e. length × width × height). The SI unit of volume is the cubic meter; however, this measurement is too large for most scientific work so scientists normally use cubic decimeters (.1 of a meter)3 to measure volume. One cubic decimeter (1 dm)3 is equal to 1 liter (l).

C. Weight is a measure of the pull of gravity on an object C. Weight is a measure of the pull of gravity on an object. The SI unit of weight is the new-ton. Since the pull of gravity differs when you leave the earth and experiments are now conducted in space, scientists commonly measure the mass of an object, which is how much matter is in something. (For example, the moon’s gravity is approximately one-sixth that of the earth.) The SI unit of mass is the gram.

D. Temperature is the amount of heat in something D. Temperature is the amount of heat in something. The SI unit for measuring temperature is degrees Kelvin. One degree Kelvin is equal to one degree Celsius which is the common unit of measurement for the metric system. The metric system of measuring temperature also is based on 100. For example, there are 100° from the temperature at which water freezes to the temperature at which water boils. Common temperature measurements in Celsius are 18° Celsius—room temperature, 37° Celsius—body temperature.

E. Area is based on measurements of length (i. e. length × width) E. Area is based on measurements of length (i.e. length × width). The SI unit for area is the square meter (m 2 ). However, when measuring plots of land for agricultural purposes, the hectare (ha) is normally used instead of the square meter. 1 hectare = 10,000 square meters.

How can numbers be converted within the metric system? Numbers can be converted within the metric system by moving the decimal points. In order to convert numbers, move the decimal points using the prefixes in front of the basic unit. When moving from a smaller unit to a larger unit, move the decimal point to the left. When moving from a larger unit to a smaller unit, move the decimal point to the right.

Example 1: If trying to move from 3 cm to _____ hm, move the decimal point four places to the left. The answer would then be .0003 hm. Example 2: If trying to move from 16 l to _____ ml, move the decimal point three places to the right. The answer would then be 16,000 ml. Example 3: If trying to move from 2.62 g to _____ kg, move the decimal point three places to the left. The answer would then be .00262 kg.

How can numbers be converted from one system of units to another system of units? Dimensional analysis is a means of converting from one system of units to another. 1. The key idea is to get the final unit you want fixed in your mind and work toward that unit. 2. The key operation is to multiply and divide units, just like numbers. 3. The key strategy is to set up multiplication or divisions to get all unwanted units to cancel. If all unwanted units do not cancel out, you will know you have set up the problem incorrectly.

Step 1: Realize that your outcome unit is cm. Example 1: 15 in = _____ cm Step 1: Realize that your outcome unit is cm. Step 2: Structure your derived equation so that the units cancel out leaving only the desired outcome unit. in × cm/in = cm Step 3: Place the numbers into the derived equation using the equivalents that you have learned. At least one volume, length, and weight equivalent should be committed to memory. The most commonly used equivalents are 1 gallon =3.79 liters, 1 inch =2.54cm, 1 pound =.45 kg. By knowing only one equivalent conversion and understanding prefixes, you can do any conversion.

Step 4: Perform the mathematical task as indicated by the equation. 15 in × (2.54 cm / 1 in) = Note: Place the equivalent in the equation as a proportion. Step 4: Perform the mathematical task as indicated by the equation. Note: In mathematics, the term “per” refers to division, as 2.54 cm per inch. 15 in × (2.54 cm / 1 in) = 38.1 cm therefore, 15 in = 38.1 cm

Step 1: The desired outcome unit is yd. Example 2: 15 in = _____ yds Step 1: The desired outcome unit is yd. Step 2: Derive an equation that will yield the desired outcome unit. in × yd/in = yd Step 3: Put the numbers into the derived equation, placing the appropriate equivalent in the proportion position. 15 in × (1 yd / 36 in) = .42 yd (rounded off to the nearest tenth)

Review/Summary What are the types of measurement used in our country? What are the metric prefixes and units used for measuring length, volume, weight, temperature, and area? How can numbers be converted within the metric system? How can numbers be converted from one system of units to another system of units?