Science in the Natural World Chapter 1

Why Do Scientists Use a Standard Measurement System? Scientists use units to measure quantities more accurately, rather than using handfuls and pinches. Do you think you can get two handfuls of beans that weight the same?

Why Do Scientists Use a Standard Measurement System? By using the same units, scientists around the world can repeat experiments with exact quantities. The metric system is based on scales of 10. Scientists use a version of the metric system called the International System of Units (or SI for short). SI allows scientists to compare data and communicate their results.

Examples of SI units you know or use?

Length/Distance The SI unit for length and distance is the meter (m) Kilometer (km)= 1000m 1 meter (m)= 100 centimeters (cm) 1 meter(m)=1000 millimeters (mm) 1 centimeter (cm)= 10 millimeters (mm)

Mass Mass is the amount of matter in an object Weight is mass + the force of gravity The SI unit for mass is the kilogram (kg) For smaller masses grams (g) or milligrams (mg) are used Gravity is lower on the moon, so you would weight less, but your MASS is the same in both places.

Volume Volume is how much space an object or substance takes up. What is a measurement of volume you use all the time? SI unit of volume is the cubic meter (m^3) There is also Liters (L) and Cubic Centimeters (cm^3)

volume 1m^3 = 1,000,000 cm^3 1cm^3 = 1mL 1L = 1,000 mL So 1L = 1,000 cm^3 How many Liters are in a m^3?

Density Density = mass divided by volume, in other words how much mass is in a confined volume. SI units are Kilograms per cubic meter (kg/m^3) There are also (g/cm^3) or (g/mL) Density determines what floats and what sinks, if the density of something is higher than water’s, the object or substance will sink.

Temperature Most common unit for temperature is Degrees Celsius, but the SI unit is degrees kelvin Kelvin = celsius – 273.15 degrees. The celsius scale is defined by the freezing point of water (what is the freezing point of water in Celsius?) And the boiling point of water (what is the temperature in celsius at which water boils?

Time You use time every day, what are some units of time that you know? What are some ways that you get timed every day? The SI unit for time are seconds Clocks and watches are commonly used to measure time, for more accurate timing there are also chronometers.

1.4 Mathematics and Science What math skills do scientists use? Estimation, accuracy, precision, and significant figures.

Estimation An estimate is an approximation of a number based on a reasonable assumption. Estimate how much your textbook weighs….. Scientists use estimates only when they cant get exact numbers Estimates can be based on indirect measurements, calculations and models. Horses are measured by palms, that is a kind of indirect measurement.

ACCURACY VS PRECISION Accuracy = how exact a measurement is

ACCURACY VS PRECISION Precision refers to how close measurements are to each other

Significant Figures Communicate how precise measurements are. All digits measured exactly + one estimated digit. Look at figure 2 in your workbook and work on the problems. Complete assess your understanding section.

What Math Tools Do Scientists Use? Scientist use tools to analyze data, which include: Percent error Mean Median Mode Range Checking the reasonableness of Data

Percent Error A way to determine how accurate a value is. Low percent error = very accurate High percent error = not accurate Complete the MATH! Sample Problem in your workbook.

Mean It is the numerical average of a set of numbers. To find it, add all the numbers, then count how many numbers you had. Then divide the sum you added by the number you counted. Complete the Mean for page 37

Median It is the number in the middle of a set of values. To find the mean list the numbers from smallest to greatest and find the number in the middle. If there is an even number of values take the two middle ones, add them together and divide by two. Find the median for the egg data in page 37

Mode It is the number that appears the most times in a set of values. Find the mode for the egg data set on page 37

Range It is the difference between the greatest and the smallest value in a data set. To find it, subtract the smallest value from the largest one. Find the range for the egg data set on page 37.

Reasonable and Anomalous Data If a scientist records ocean water temperature for five days, and the first four days he/she records 26*C, 23*C, 25*C, 24*C. Then on the fifth day he/she asks a student to do it, and the student records 81. Is that value reasonable? Does it make sense?

Reasonable and Anomalous Data Anomalous Data: values that do not “fit” with the rest of the data set. Look at figure 4 on page 38, analyze the collected data and describe an unknown variable that could have affected the data. For hw, study for the Measurement Quiz, complete the “Assess your Understanding” questions for section 1.4, and read section 1.5 “Graphs in Science” Section 1.4 will be ripped out of the workbook and collected on Monday, no late grades so don’t forget!!!!