Catalyst (5 min) Complete the following calculations: – 4.0 = ________ – 2.7 = _______________ – 7.0 = ___________ = ________ 5. X = 363, X = _________ You will need to bring a calculator tomorrow!

Catalyst (5 min) Complete the following calculations: – 4.0 = ________ – 2.7 = ________ – 7.0 = ______ = ________ 5. X = 363, X = _________

The Metric System SI (System International) 10/5/10

Metric System Used by every country in the world, except the USA. Always used by scientists. Also called SI, which is French stands for System International. Based on the number 10, so it’s easy!

Measuring Length Length is the distance between two points. Basic unit = meter. Meter = m ruler or meter stick

Measuring Mass Mass is the amount of matter (stuff) that makes up an object. Basic unit = gram.(g) Tool: scales

Measuring Volume Volume is the amount of space contained in an object. Base unit = Liter (L). We measure volume with a graduated cylinder or beaker.

Measuring Temperature Temperature is the measure of the average heat or heat energy Basic unit= degree Celcius (°C) or Kelvin (K) We use thermometers to measure temperature. K = °C + 273

Let’s review our basic units!!! Length  Meter (m) Mass  Gram (g) Volume  Liter (L) Temperature  °C or K We need more accuracy We can’t measure everything with just basic units We need prefixes!

Metric Prefixes We add prefixes BEFORE basic units to make new units that are smaller or bigger Common prefixes from large to small: kilo (k) = 1000 centi (c ) = 1/100th milli (m) = 1/1000th Example: kilogram (kg) = 1000 g 100 centimeters (cm) = 1 m 1000 milliliters (mL) = 1 L

Why is measurement important? We make measurements in the lab We use measurements to back up our conclusions If our measurements are not accurate, our conclusions are not supported!

When is measurement important? Why does messing up the dosage of medicine cause more problems for children than adults?  Children have smaller bodies  A small amount of medicine has a larger affect in a child than in an adult KEY POINT: When measuring, we need to be accurate and precise, or end up with some serious consequences!

Accuracy Definition: how close a measured value is to an accepted value KEY POINT: accurate measurements = meaningful Accurate Not Accurate

Precision Definition: how close a series of measurements are to one another Key Point: more precision = more support if accurate Precise Not Precise

Accuracy vs. Precision Accuracy: measurement vs. actual value Precision: similarity between repeated measurements YOU CAN BE ACCURATE, PRECISE, BOTH OR NEITHER! Accurate Precise, not accurate Accurate AND Precise Not Accurate, Not Precise

Error Error is a measurement of accuracy Higher error = less accurate measurement (BAD!!) Equation: error = |experimental – actual|

Example: Julio weighed himself at the gym. The scale said he weighed 79.3 kg, but he really weighs 81.6 kg. What is the error in his measurement? error = |experimental – actual| = |79.3 – 81.6| = |-2.3| = 2.3 kg

Example as a Class! Christian measured the length of his Snickers bar to be 10 cm long. In reality, the candy bar is actually 9.5 cm long. What is the error in his measurement?? Error = |experimental – actual| = |10 cm – 9.5 cm| = |-0.5 cm| 0.5 cm!

BRING A CALCULATOR TOMORROW!

Classwork Assignment Select TWO of the following problems and calculate the error in the following measurements on a separate sheet of paper. Turn into the homework stack when finished. Don’t foget units in your answers! 1. Experimental measurement: 4.5 km, Actual measurement: 3.2 km 2. Experimental measurement: 12.5 L, Actual measurement: 11.4 L 3. Sandra measured the mass of a ball to be 55.0 g, but the ball is really 53.9 g. 4. Juan thought the field looked about m, but it was actually m long. 5. Maria thought the glass held 344 mL of liquid, but it only had 315 mL.