Scientific Method

What is Science?

• Science is a method for studying the natural world.

• It is a process that uses observation and investigation to gain knowledge about events in nature.

Scientific Method

• An organized set of investigation procedures is called a scientific method.

• Six common steps found in scientific methods are shown.

Controlled Experiment

• Variables – factors in an experiment that can be changed.

• Independent Variable – The variable that you change in the experiment (the amount of fertilizer used).

• Dependent Variable – the variable that may change due to the independent variable (growth in the height of the plant).

Controlled Experiment (2)

• Control Group – A group that is not changed in an experiment (one plant that is not fertilized).

• Experimental Group – A group in an experiment that has had one variable changed (The plants that were given fertilizer).

• Constants – A factor that does not change when other variables change (type of plant, type of fertilizer, amount of sunlight, size of the pots).

Measurement

• Quantitative information (qualitative data would be descriptions of your observations).

• Measurements represent quantities (something that has magnitude, size, or amount).

SI Measurement

• Scientist use the International System of Units (SI).

SI Base Units

• There are seven SI base units (meter, kilogram, second, kelvin, mole, ampere, candela). All other SI units are derived from these.

• Mass is the measure of the quantity of matter (SI unit is the kilogram). Measured by using a balance. Weight is a measure of the gravitational pull on matter and is measured by using a spring scale.

• The SI unit for length is the meter.

Derived SI Units

• Derived units are produced by multiplying or dividing standard units.

• The SI unit for volume is m3 (1mL = 1cm3)

Derived SI Units (2)

• Density is the ratio of mass to volume, or mass divided by volume (D = m/v). The SI unit for density is kg/m3. In the lab you will usually see density expressed as g/mL or g/cm3.

Conversion Factors

• Ratio derived from the equality between two different units that can be used to convert from one unit to another.

• Example: In one dollar there are 4 quarters 4 quarters or 1 dollar 1 dollar 4 quarters

Scientific Notation

• Numbers are written in the form M x 10n, where the factor M is a number greater or equal to 1 but less than 10 and n is a whole number.

• 65,000 km = 6.5 x 104 km (when numbers are written in scientific notation only significant figures are shown).

• 0.00012 mm = 1.2 x 10-4 mm

Scientific Notation (2)

• M is determined by moving the decimal point in the original number to the left or the right so that only one nonzero digit remains to the left of the decimal point.

• n is determined by counting the number of places that you moved the decimal point. If you moved it to the left, n is positive. If you moved it to the right, n is negative.