Unit 1 (Introduction to Chemistry) Flashcards
Define these: Scientific Method
Chemistry
Matter
Mass
Energy
Weight
An organized approach to solve problems
The study of matter and the changes it undergoes.
anything that has mass and volume (everything)
the amount of matter in an object (how much stuff)
anything that can do work or produce heat.
The force of gravity acting on an object’s mass.
Explain the 5 steps of the scientific method
- Obeserve (Use your five senses, Define the problem)
- Hypotheses (”Educated guess”, Reasonable explanations for what was observed)
- Experiments (Tests each hypothesis in order to prove/disprove them)
- Analysis (Compares the results from the experiment to the original hypothesis)
- Conclusion (Theory, A hypothesis supported by experimental evidence)
What is the difference between a law and a theory
Law: Used to describe a natural phenomenon which has been tested over a long period of time under different conditions
Theory: Describes how a phenomenon happens. Can’t be tested.
Identify which properties solids liquids and gasses have
shape
volume
compressible
density
Solids
* Definite shape
* Definite volume
* Not compressible
* High density
Liquids
* Indefinite shape
* Definite volume
* Not compressible
* Less dense than solids
Gas
* Indefinite shape
* Indefinite volume
* Are compressible
* Very low density
Explain what a pure substance is and the two types
* Elements + examples
* Compounds + examples
Pure substances have uniform and definite composition
* Elements: Elements found on the Periodic Table (approx 118) Symbols like H, He, etc.
* Compounds: formed when elements chemically combine: H2O, CO2, NO2
Explain what mixtures are and the two types of mixtures
* heterogeneous mixures
* homogeneous mixtures
Two or more pure substances physically mixed together. Substances are blended, but not bonded. Don’t have definite compositions (so no fixed ratio).
* Heterogeneous mixtures: do not have a uniform composition. Parts of the mixture can be physically seen and “picked out” of the mixture. Examples: Cereal, pizza, salad
* Homogeneous mixtures: has a uniform composition Parts of the mixture cannot be “picked out” Examples: sugar water, milk
Explain and list examples of physical properties and chemical properties
* physical + examples
* chemical + examples
Physical: properties that can be measured or observed without changing the identity (or composition of a substance). Can be seen without chemical reactions. Examples: color, odor, texture, taste, freezing point, melting point, density, mass, hardness
Chemical: Properties that indicate how a substance reacts with other substances. Can only be seen through chemical reactions. Examples: flammable, combustible, burnable, “Reacts with”
Explain and list examples of physical and chemical CHANGES. Also explain the law of conservation of mass.
* physical changes + examples
* chemical changes + examples
* law of conservation of mass
Physical: Changes in appearance without changing composition Examples: Examples: cutting, breaking, pulverizing, changes in state
Chemical: One or more substances react to form new substances with different chemical and physical properties. The beginning substance is different than the ending substance. Have chemical equations. Examples: Rusting, burning, corrosion, digestion, respiration, decaying
Law of conservation of mass: Law of Conservation of Mass: In any chemical or physical change, matter cannot be created or destroyed. So products = mass of reactants.
Define these terms and give examples for quantitative vs quality measurements. Also give examples for accuracy vs precision
Measurement
Qualitative measurements + examples
Quantitative measurements + examples
Accuracy + examples
Precision + examples
- Measurement: A type of observation
- Qualitative measurements: descriptive EX: hot cold heavy light big blue furry
- Quantitative measurements: observation made with a measuring instrument and includes both a number unit. Ex: ruler, balance, thermometer, graduated cylinder, 13.5 C, 25 kg
- Accuracy: How close a measurement is to the true or accepted value
- Precision How close multiple measurements are to each other
Not accurate, precise
32.18g
32.18g
32.18g
Accurate, precise
50.00g
49.99g
50.00g
Explain Scientific Notation
* what it is
* the 2 parts of it
* how to convert and solve problems
It is a shorthand way for writing very large/small numbers. Has 2 parts, the Coefficient and Power of 10.
Use the sci option on the calculator. Also use exponents parenthesis and solve the problem. Keep in mind it could be inaccurate on the calculator.
There is uncertainty in all measurements. Explain
1. what this means.
2. what this depends on
3. how many figures an exact number has
Means all numbers read directly off of the measuring device PLUS one extra estimated digit.
The amount of definite digits depends on the measuring device.
An exact number has no uncertainty, and therefore has an infinite number of figures
How do you determine how many significant figures a number has? 4 things
- All non zero digits are significant
- Leading zeros are never significant (zeros to the left)
- Captive zeros are always significant (zeros in the middle)
- Trailing zeros are sometimes significant (zeros at the end) ________________________________________________________________________
a) They are significant if the number contains a decimal point
b) They are not sig. if the number does not contain a decimal point
Explain how to round scientific numbers in addition/subtraction, and in multiplication/divison.
addition/subtraction -
The answer is rounded to the same number of decimal places as the number used in calculation with the least decimal places.
multiplication/division -
rounded to the same number of sig figs. as the number used in calculation with the least significant figures.
