Chapter 2 Flashcards
Observation
is the use of the senses to obtain information by taking measurement and collecting data.
Qualitative
data that is descriptive
Quantitative
data that is numerical
Hypothesis
when scientists use generalizations about the data to formulate a testable statement
you make predictions
it is written as an “if-then” statement
System
is a specific portion of matter in a given region of space that has been selected for study during an experiment/observation.
EX. when observing a reaction in a test tube, the test tube and its contents is a system
Variable
any condition that changes
any change observed is due to a variable
Constant
the things in the experiment that stays the same for every group.
Control
the experimental support or conditions that remain constant
Independent variable
what you are looking at for changes; constantly changes(x-value)
Dependent variable
the outcome/result of the independent variable. (y-value) depends on the x-value
Theory
a broad generalization that explains a body of facts or phenomena
usually successful in predicting
EX. gravity theory
Model
In science, it is more than a physical object but an explanation of how phenomena occur and how data is related
Can be used verbally, visually, or mathematically
EX. atomic model of matter
Derived units
a measurement calculated by using 2 or more simple measurements
EX. volume, area, density, and speed
Accuracy
how close your measurements are to what you should have got
use percent error to check for accuracy
Precision
how close your measurements are to each other
Percentage error
the percentage in what you were of in an experiment using the actual value and experimental value.
Human Error: reading numbers wrong or using wrong units on accident.
Instrument Error: problem with the equipment itself or causing uncertainty with exactness of measurements.
Scientific notation
a way of expressing really small or really large mathematical values in a workable way
Format: M x 10n
Variable M: CAN’T go over or be equal to 10
Variable n: must be an integer
EX. 1,000 in scientific notation is 1 x 103
Density
how compact or squished a substance is; mass per unit of volume
Formula: mass/volume
Mass
how much something is made of: molecules, protons, etc…
Measure using a balance(grams)
Volume
the space something takes up
Measure using a graduated cylinder(liters), displacement, or LxWxH(mL)
Scientific method
This is a logical approach to solving problems by observing/collecting data, formulating hypotheses, testing hypotheses, and formulating theories that are supported by data.
When you test a hypothesis and it is not supported, you go back to formulating hypotheses and reject or remake a hypothesis.
Experimental design
This involves carrying out a procedure under controlled conditions to make observations and collect data. It allows us to learn more about chemistry, matter, and more.
Types of scientific models
Visual, verbal, or mathematical scientific models.
How to use SI units (base and prefixes)
Use the SI units prefixes when you are taking measurements and when solving problems. Use SI unit bases with dimensional analysis to help convert them from one to another
Base SI units
The SI base units are: Distance, volume, mass, weight, temperature, time, energy, and current.
How to convert units using dimensional analysis
To convert units using dimensional analysis, you must use conversion factors. You have to find the base unit for example, meters. Then if it asks to convert 1 meter to 22 dekameters, you use the base units as conversion factors and solve.
How to calculate percentage error
% error = (experimental value - actual value) / actual value
What causes error and how to limit error in the lab
Human error is when we read numbers wrong when weighing/measuring or we use the wrong units and mess up. Then, there are instrument errors/limits where there is a specific problem with the equipment(calibration) or different tools don’t measure as specific causing uncertainty in answers.
To limit error, use the digit of uncertainty where if you measure with a ruler that measures to the tenths, then you round to the hundredths.
Why significant figures are necessary
They are necessary so that it makes it easier for whoever is reading your work, understands how specific your data was or was not. It also allows for easier calculations and better numbers to use and compare.
How to count significant figures (the rules)
1) All nonzero digits are significant
2) Zeros at the end of a number AND to the right of the decimal point are significant
3) Zeros BETWEEN significant figures are significant
4) Zeros BEFORE all nonzero digits are NOT significant
5) Zeros at the END of a number AND to the LEFT of the decimal point MAY be significant
How to round numbers using significant figures
When rounding using significant figures, it depends on what you are rounding from. it depends on the number of sig figs in both numbers and when you use it.
How to calculate using the appropriate number of sig figs
In addition/subtraction, you must round to the sig fig in which the number ends first. Then, you add/subtract the numbers and add to where the sig figs end.
In multiplication/division, you find the sig figs in the numbers you are multiplying or dividing. The lowest number of sig figs in one of your reactants is the number you round to when you multiply/divide.
How to put a number into scientific notation
To put a number into scientific notation, you must make the number, M, less than 10 but greater than 1. However many places you move the decimal point to the left or right, that is how much you put ten to the power of. if you move the decimal left, you put ten to a positive exponent but if you move the decimal to the right, make the exponent negative.
How to take a number out of scientific notation
When taking a number out of scientific notation, if the exponent is negative, you move the decimal point to the left however many times the 10 is put to the power. If the exponent is positive, you move the decimal point to the right however many times the 10 is put to the power.
How to calculate using scientific notation
When using scientific notation, and you multiply two different numbers, you multiply the number, M, by each other. Then, you add the exponents of the 10*n and get your new number. Finally, depending on your multiplication of M, you might need to move the decimal left or right which then you need to increase or decrease the exponent
How to calculate density
You do the amount of mass divided by the volume.
What are the 2 things each measurement is made of?
Number and base
How many of each may you have between independent and dependent variables?
Independent: Only one
Dependent: 1 or more
