Chemistry and Measurement Definitions and Formulas Flashcards
What is Chemistry?
- The study of composition, properties, structure and transformations of matter.
- Knowing how changes take place, allows chemist to:
- Make more substances
- Use clues to find new processes and create new products.
- Inhibit certain changes to preserve useful products.
Experiment
Observation of natural phenomena carried out in a controlled manner so that the results can be duplicated and rational conclusions obtain.
Law
Concise statement or mathematical equation about a fundamental relationship or regularity of nature.
Hypothesis
A tentative explanation of some regularity of nature.
Theory
tested explanation of basic natural phenomena.
Mass
The quantity of matter in a material
Matter
general term for the material things around us, defined as whatever occupies space and can be perceived by our senses.
Law of conservation of mass
The total mass remains constant during a chemical change (chemical reaction)
Who is Antonine Lavoisier?
- Wrote the Traite Elementaire de Chemie (Basic treaties on chemistry)
- Father of Modern Chemistry
- Used the Metric system
- Insisted on using balances in chemical research
- had explained combustion.
Scientific Method
- Framing of laws, hypothisis or theories and the conducting of more experiments.
- Therefore scientific knowledge is testable, reproducible, explanatory, predictive and tentative.
Weight
The force of gravity exerted on a substance or gravitational attraction of earth on the body.
Physical States
- Given kind of matter exists in different physical forms under different conditions
- Solid:
- incompressible, fixed shape and volume
- Liquid
- Fixed volume, no fixed shape, incompressible
- Gas
- Takes shape and size of container, easily compresible fluid.
- Solid:
Physical Change
A change in the form of matter but not in its chemical identity.
Chemical Constitution
Element, compound or mixture
Properties
Characteristics used to describe or identify matter.
Chemical change (Chemical reaction)
A change in which one or more kinds of matter are transformed into a new kind of matte or several new kinds of matter.
Physical Property
Characteristic that can be observed for a material without changing its chemical identity.
Chemical property
Characteristic of a material involving its chemical change.
Extensive Property
Values that depend upon the sample size.
Intensive Property
Values that do not depend on amount of the sample
E.g. temperature and melting point of water.
Substances
Kind of matter that cannot be seperated into other kinds of matter by any physical process.
Element
Substance that cannot be decomposed by any chemical reaction into simpler substances.
Compound
Substance composed of two or more elements chemically combined.
Law of definite proportions
- also known as the law of constant compostion
- a pure compound, whatever its source, always contains definite or constant proportions of the elements by mass.
Mixtures
A material that can be seperated by physical means into two or more substances. Classified into homogeneous and heterogeneous.
Homogeneous Mixtures
- also known as a solution.
- uniform in its properties throughout given samples.
Heterogeneous Mixture
Physically distinct parts, each with different properties.
Phase Mixture
one of several different homogenous materilas present in the portion of matter under study.
Measurement
Comparison of a physical quantity to be measured with a unit of measurement - a fixed standard of measurement.
Purpose of measurement
- To be able to reproduce an experiment
- To make sure that the correct concentration or amount is used.
Precision
- Refers to the closeness of the set of values obtained from obtained from identical measurements of a quantity.
- Or, or how well a number of independent measurements agree with one another.
Accuracy
- the closeness of a single measurement to its true value.
- or, how close the true value a given measurement is.
- For maximum reliability, the number obtained for measure chould contain all the digits that are known, plus one digit that is estimated. This last digit introduces some uncertainty.
Significant Figures
- Those digits in a measured number (or in the result of a calculation with measured numbers) that include all certain digits plus a final digit having some uncertainty.
Number of Significant figures
- Refers to the number of digits reported for the value of a measured or calculated quantity, indicating the precision of the value.
- The more significant the figure, the more precise the measurement.
What are the rules for Significant Figures?
- Zeros in the middle of a number are like any other digit; they are always significant.
- 4.803 cm has four significant digits
- Zeros at the beginning of a number are not significant; they act to locate the decimal point
- 0.00661 g has three significant digits
- Zeros at the end of a number and before the decimal point may or may not be significant.
- 900 cm may be one, two or three significant figures
- if 900. cm then there is three significant digits.
Scientific Notation
The representation of a number in the form A x 10 n ,
where
- ‘A’ is a number with a single non-zero digit to the left of the decimal point
- ‘n’ is an integer, or whole number
Exact Numbers
- Number that arises when you count items or sometimes when you define a unit.
- They have no effect on the number of significant figures in a calculation.
Significant Figures in Multiplication and Division
- Give as many significant figures in the answer as there are in the measurement with the least number of significant figures.
- e.g. 190.6 x 2.3 = 438.38 => 440
Significant Figures in Addition and Subtractions
- Give the same number of decimal places as the value with the fewest decimal places.
- 125.17 + 129 + 52.2 = 306
Rounding
- The procedure of dropping nonsignificant digits in a calculation result and adjusting the last digit reported
- If the digit is 5 or greater, add 1 to the last digit and drop all digits to the right.
- If the digits is 5 or less. simply drop it and all digits to the right.
What are SI units?
- 1790, the French Academy of Sciences devised the metric system.
- International System of units or SI after the French le Système International d’Unités, which is a modernized version of the metric system established in France was adopted in 1960 by the General Conference of Weights and Measures.
What are the seven base units of SI?
- Mass, kilogram, kg
- Length, meter, m
- temperature, kelvin, K
- Amount of substance, mole, mol
- Time, second, s
- Electric current, ampere, A
- Luminous intensity, candela, cd
Formula to convert Celsius to Kelvin?
Formula to convert Celsius to Fehrenheit?
Formula to convert Fehrenheit to Celsius?
Derived Units
Units expressed by using one or more of the seven base units
- Area, length squared,m2
- Volume, length cubed, m3
- Density, mass per unit volume, kg/m3
- Speed, distance traveled per unit time, m/s
- Acceleration, speed changed per unit time, m/s2
- Force, Mass times acceleration, kg • m/s2, also known as a Newton
- Pressure, force per unit area, kg/(ms2), also known as a Pascal
- Energy, force times distance traveled, kg • m2/s2 , also known as a Joule
Density
Is the mass of an object divided by the volume: d =m/V
g/cm3 for a solid
g/mL for a liquid
Density of a substance
- Can be used to identify the substance
- Is temperature dependent because volume changes with temperature. Specify the temperature at which the density was measured.
What is dimensional analysis?
- Also known as: factor-label method.
- Method of calculation in which one carries along the units of the quantities
- We can use known relationships among the units or factors to fin the unknown quantity.
- All conversion factors are numerically equal to 1.
(Original Qty) x (Conversion factor) = (Equivalent Qty)
What are the steps for using dimensional analysis?
- Find out the unit given
- Find out the unit required in the answer
- Find a relationship between the given units and the required answer units.
- Solve the problem.
