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Learn about the scientific method, controlled experiments, SI measurement, scientific notation, organizing data, and density calculations in this comprehensive guide.
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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 change. • 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.
Organizing Data • A graph is a pictorial representation of information recorded in a data table. It is used to show a relationship between two or more factors.
Types of Graphs • Line graphs are best for displaying data that change. It best shows the relationship between two variables. A variable is anything that can change in an experiment. Line graphs are made with the x-axis showing the independent variable (manipulated variable) and the y-axis showing the dependent variable (responding variable).
Types of Graphs (2) • Bar graphs are best for comparing data for several individual items or events. Bar graphs use a series of columns to display data.
Types of Graphs (3) • Pie charts are best for displaying data that are parts of a whole.
Density • Density is a physical property of a substance. Physical properties can be observed or measured without changing a substance. • Other physical properties of substances include shape, color, odor, and texture.
Calculating Density • Density is calculated by dividing an object’s mass by its volume. • Density = mass/volume or D = m/v
Low and High Density • A substance with a low density is referred to as being “light”. An example is Styrofoam. • A substance with a high density is referred to as being “heavy”. An example is iron. • Density of a liquid or solid is reported in units of grams per cubic centimeter (g/cm3).