1a. Foundational Skills Flashcards
What is a pure substance?
A pure substance is matter that has distinct properties and a composition that does not vary from sample to sample.
What does a not pure substance vs a pure substance?
A pure substance can be described as atoms and compounds, as they are singular or are properly combined. Things such as mixtures are not pure substances.
What are elements?
Elements are substances that cannot be decomposed into simpler substances. Each element is composed of at least one type of atom.
What are compounds?
A compound are substances composed of two or more elements. They contain two or more kinds of atoms.
What are mixtures?
Mixtures are combinations of two or more substances in which each substance retains its chemical identity.
What is a certain digit?
Certain digits are the numbers that remain reguardless of who makes the measurement.
What is an uncertain digit?
Uncertain digits are estimated digits to the right of the certain digit.
What is a random error?
Random errors are when a measurement has an equal probability of being high or low.
What is a systematic error?
A systematic error is either ALWAYS HIGH or ALWAYS LOW.
No error, systematic error, random error. (Photograph, tap 5 if you could replicate after seeing it AND understand it.)
When do nonzero integers count as significant figures?
Nonzero integers ALWAYS count as significant figures?
What are leading zeros?
Leading zeros are zeros that precede all the nonzero integers. (Example: 0.0450200. The 0.0 in front of the 4502 are classified as leading zeros.)
What are captive zeros?
Captive zeros are the zeros between nonzero digits. They always count as significant figures. (Example: Take the number 0.0450200. The 0 in between the 45 and the 2 is known as a captive zero).
What are trailing zeros?
Trailing zeros are zeros at the right end of the number. They are only significant if there is a decimal point. (Example: In the number 100, there is one significant figure, but in 100.0, there are three significant figures.
What is the law of constant composition?
The law of constant compotion is the observation that the elemental composition of a compound that is always the same.
Which five elements make up 90% of the earth’s crust?
Oxygen, silicon, aluminum, iron, and calcium
What is the formula for % of error?
accepted value - experimental value / accepted value x 100
What are common sources of error?
Common sources of error include:
–> Instrumental error (when the instruments being used are inaccurate)
–> Environmental error (an uncommon factor in the environment, such as wind)
–> Procedural error (different procedures are used to answer the same question, leading to slightly different responses)
–> Human error (carelessness or human mistake/limitation)
What is accuracy?
Accuracy is a measure of how close a measurement is to the correct or accepted value of the quantity being measured.
What is precision?
Precision is a measure of how close a series of measurements are to one another. Precise measurements are highly reproducible, even if the measurements are not near the correct value.
What is variability?
Variability is a measure of how spread out (or “scattered”) the numbers are in a set of numbers.
What is uncertainty?
Uncertainty is the range of possible values within which the true value of the measurement lies.
What is the relationship between precision, variability, and uncertainty?
Precision is how close something is to the accepted value, and uncertainty is the level of human limitation we have on finding this accepted value. Variability is how spread out the uncertain decision is from the precise accepted value.
What is standard deviation?
The standard deviation in a series of data is a measure of how dispersed the data is in relation to the mean.
What is a significant figure?
The term significant figures refers to the number of important single digits (0 through 9 inclusive) in the coefficient of an expression in scientific notation . The number of significant figures in an expression indicates the confidence or precision with which an engineer or scientist states a quantity.
Rules for significant figures: Adding/Subtracting
Result = same number of decimal places as the measurement with the least amount of decimal places
Rules for significant figures: Multiplying/Dividing
Result = same number of sig figs as the measurement with the smallest number of sig figs
Significant figures: Atlantic-Pacific method
The rule states that if a decimal point is absent, then the zeroes on the Atlantic/right side are insignificant. If a decimal point is Present, then the zeroes on the Pacific/left side are insignificant.
Obtaining uncertainty measurements from a device
Take the smallest possible unit, and divide it in half. For example, if you have a meter stick, the smallest unit is 1 mm. Divided by 2, that’s 0.5 mm, which is also equal to 0.05 cm. That’s the uncertainty.
SI Units
meter, kilogram, kelvin, second, mole
SI quantities
length, mass, temperature, time, amount of substance
What are the two advantages to exponential notation?
- Able to express very large/small numbers concisely
2. Shows the sig figs unambiguously
What is the formula for density?
D = M / V
As the precision of a measurement device improves, what else occurs?
The # of sig figs increases, the uncertainty interval becomes smaller, and the variability in multiple measurements becomes smaller
