how do people gather scientific information?. scientific method i’m tad identify a problem make a...

How do people gather scientific information?

Scientific MethodI’M TADIdentify a ProblemMake a HypothesisTest the Hypothesis (Perform an Experiment)Analyze the DataDraw Conclusions

Sometimes a 6th step is included in which you share your conclusions with others

Hypothesis vs. Theory vs. LawHypothesis – An educated guess

Scientific Theory – A hypothesis supported by many experiments

Scientific Law - facts of nature accepted as truth

Controlled ExperimentsA Controlled Experment is one where only

one variable is tested at a time

Why is it important to use controlled experiments?

Controlled ExperimentsControl Group – the group that doesn’t

receive the experimental treatment, a standard for comparison

Independent Variable – the variable in the experiment you change

Dependent Variable – the variable in the experiment that only changes because you changed the independent variable

Controlled ExperimentsExample:

Merck decides to test a new antibiotic to see if it will cure patients’ sinus infections. Some testers are given pills containing the new antibiotic and others are given a placebo, or sugar pill.

Identify:ControlIndependent VariableDependent Variable

The Metric SystemIn the US, we use the English system of units

(lbs, in., oz., etc.)The rest of the world, including the scientific

world, uses the SI (Systeme Internationale) or Metric System

Why?It’s universal (used everywhere but US)Units are converted based on factors of 10

SI UnitsWhat are the SI base units for these

measurements?

Length/distance?Meter (m)

Volume?Liter (L)

Time?Seconds (s)

SI UnitsWhat are the SI base units for these

measurements?

Temperature?Kelvin (K), the absolute scale for Celsius (°C)

Mass?Grams (g)?We use grams for the base unit, but kilograms

(kg) are considered the SI unit for mass

Metric ConversionsWe use SI units because it’s easy to convert

between magnitudesWe use a prefix to identify the magnitude of

the measurementExamples: kg, cm, mL

To remember the prefixes, use the mnemonic:

King Henry Died by Drinking Chocolate Milk

Metric PrefixesPrefix Symbol Magnitude

Kilo k 1,000(103)

Hecto h 100 (102)

Deca da 10 (101)

base unit g, L, m 1 (100)

Deci d 0.1 (10-1)

Centi c 0.01 (10-2)

Milli m 0.001 (10-3)

Converting between Metric UnitsTo convert between metric units, count how

many spaces are between the unitsMove the decimal point that many spaces in

the direction you counted towardsExample 1: 10m = ? cm

Answer: 1,000cmExample 2: 10mL = ? hL

Answer: 0.0001hLkilo hecto deca base deci centi milli

DensityThe amount of matter in a given amount of

space is known as Density(D)D = m/VCommon units: g/mL, g/cm3

Note: 1mL = 1cm3

Example: If a 45.2g block has a volume of 11.6mL, what is it’s density?D = 45.2g/11.6mLD = 3.90g/mL

AreaA = l x wFor a square: A = side2

For a triangle: A= ½ bhCommon units: cm2, m2

Example: If a square has a length of 5cm and a width of 3cm, what is its area?A = 5cm x 3cmA = 15cm2

Matter, Mass and WeightMatter – anything with mass and volumeMass – the amount of matter in an objectWeight – the effect of gravity on an object

What is the difference between mass and weight?Gravity