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Chem.200-1.Intro
General Chemistry Ch. 1 - Introduction
| Question | Answer |
|---|---|
| Chemistry | The study of matter and its properties, the changes that matter undergoes, and the energy associated with those changes. |
| Matter | The “stuff” of the universe: anything that has mass and volume. |
| Composition of matter | The types and amounts of simpler substances that make matter up. |
| Substance | A type of matter that has a defined, fixed composition. |
| Properties | The characteristics that give each substance its unique identity. |
| Physical properties | Those that a substance shows by itself, without changing into or interacting with another substance. E.g. color, melting point, electrical conductivity, and density. |
| Physical change | Occurs when a substance alters its physical form, NOT its composition. Thus, a physical change results in different physical properties. E.g. when ice melts (water in solid form -> water in liquid form). |
| Chemical properties | Those properties that a substance shows as it changes into or interacts with another substance (or substances) e.g. flammability, corrosiveness, and reactivity with acids. |
| Chemical change, AKA: Chemical reaction | Occurs when a substance is converted into a different substance. E.g. water turns into hydrogen gas & oxygen gas after an electrical current is passed through it. |
| Examples of physical properties of copper | Malleable and ductile. A good thermal and electrical conductor. Can be melted and mixed with zinc to form brass. Density = 8.95 g/cm^3; Melting point = 1083degC; Boiling point = 2570degC |
| Examples of chemical properties of copper | Slowly forms a blue-green carbonate in moist air. Reacts with nitric acid or sulfuric acid. Slowly forms deep-blue solution in aqueous ammonia. |
| Vocab: ductile | Can be drawn out into a wire |
| Vocab: malleable | Can be hammered or pressed permanently without cracking or breaking. |
| States | Matter occurs commonly in three physical forms called states: solid, liquid and gas |
| Solid | Has a fixed shape that does not conform to the container shape |
| Liquid | Conforms to the container shape but fills the container only to the extent of the liquid’s volume; thus, a liquid forms a surface |
| Gas | Conforms to the container shape also, but it fills the entire container, and thus, does NOT form a surface |
| Atomic arrangement of solids | Particles close together and organized (e.g. in a definite pattern). |
| Atomic arrangement of liquids | Particles close together but disorganized and move randomly around each other |
| Atomic arrangement of gas | Particles far apart and disorganized |
| Difference between the physical changes of melting ice to water or heating water to gas and chemical changes | Physical changes can be reversed, which is not typically true of chemical changes. |
| Macroscopic properties and behavior | Those we can see. They are the results of submicroscopic properties and behavior. Observable changes. |
| Submicroscopic properties and behavior | Those properties and behaviors that we cannot see. Unobservable causes. |
| Energy | The ability to do work. |
| Total energy of an object | The total energy and object possesses is the sum of its potential energy and kinetic energy |
| Potential energy | The energy due to the position of the object |
| Kinetic energy | The energy due to the motion of the object |
| Energy involved: lifting up a weight and dropping it to the ground | Lifting: gives the weight potential energy. Dropping: weight converts potential energy to kinetic energy which can be used to do work, e.g. driving a stake into the ground |
| In nature: situations of _____ energy are typically favored over those of _____ energy. E.g. … | Lower; higher. E.g. The weight, when dropped, converts the potential energy to kinetic energy and transfers it thus returning to its lower level of energy. The weight is thus less stable at higher energies. |
| Energy involved: two balls attached by a spring | When you pull the balls apart, potential energy is added and the balls become less stable. When released, the potential energy is converted to kinetic energy. |
| Electrostatic forces | Opposite charges attract each other, and like charges repel |
| When work is done to separate a positive particle from a negative one… | The potential energy of the particles increases. The same principles applies when two particles with the same charged are pressed against each other. |
| The chemical potential energy of a substance (e.g. gasoline) results from… | The relative positions and the attractions and repulsions among all its particles. |
| When gasoline burns in a car engine... | Substances with higher chemical potential energy (gasoline and air) form substances with lower potential energy (exhaust gasses). The potential energy is converted to kinetic energy which powers the car. |
| Alchemy | An occult study of nature that flourished for 1500 years in northern Africa and Europe and resulted in the development of several key laboratory methods |
| Discoveries and developments made by alchemists | Alchemists invented the chemical methods of distillation, percolation, and extraction. Alchemists also encouraged the widespread acceptance of observation and experimentation. |
| Alchemists’ use of observation and experimentation replaced what approach? | The Greek approach of studying nature solely through reason. |
| Chemical investigation in the modern sense—inquiry into the causes of changes in matter—began in the late 17th century but what hampered by… | An incorrect theory of combustion (the process of burning) |
| Phlogiston theory | The theory accepted in the late 17th century which proposed that combustible materials contain varying amounts of an undetectable substance called phlogiston, which is released when material burns. |
| Antoine Lavoisier | Regarded as the father of the science of chemistry, replaced the theory incorrect phlogiston theory of combustion with the correct one through scientific inquiry and experimentation |
| How did Lavoisier demonstrate the true nature of combustion? | By heating objects while measuring their masses before and after heating, showing that heating causes substances to change and combine or separate from other substances. |
| Why did Lavoisier’s theory triumph over the phlogiston theory? | Because Lavoisier’s theory relied on quantitative, reproducible measurements, not strange properties of undetectable substances |
| Scientific method | A flexible process of creative thinking and testing aimed at objective, verifiable discoveries about how nature works |
| In general terms, the scientific method includes the following parts | 1. Observations, 2. Hypothesis, 3. Experiment, 4. Model (Theory), 5. Further experiment |
| Scientific method: Observations. What are the most useful observations? | These are the facts that our ideas must explain. The most useful observations are quantitative because they can be compared and show trends. |
| Data | Pieces of quantitative information |
| Natural Law | When the same observation is made by many investigators in many situations with no clear exceptions, it is summarized, often in mathematical terms, and called a natural law. |
| Scientific method: Hypothesis. A sound hypothesis must be _____ | A proposal made to explain an observation. A sound hypothesis must be testable. If the hypothesis is inconsistent with results, it must be revised or discarded. |
| Scientific method: Experiment. An experiment typically contains …. A well-designed experiment is … | A clear set of procedural steps that test a hypothesis. An experiment typically contains at least two variables. A well designed experiment is controlled. |
| Variables | Quantities that can have more than a single value. |
| Controlled experiment | Controlled refers to the fact that the experiment measures the effect of one variable on another while keeping all others constant. |
| For experimental results to be accepted they must be _____ | Reproducible. Not only by the person who designed the experiment, but by others. |
| Scientific method: Theory (or Model) | As hypotheses are revised according to experimental results, a model gradually emerges that describes how the observed phenomenon occurs. Theories are refined continually through further experiments. |
| Is a theory an exact representation of nature? | No, it is a simplified version of nature that can be used to make predictions about related phenomena. |
| Conversion factors | Ratios used to express a measured quantity in different units. E.g. 1mi/5280ft = 1. |
| Multiplying by a conversion factor is the same as multiplying by | 1 |
| 150mi in terms of feet. User conversion factor. | Put mi on denominator in the conversion factor because we want it to cancel out: 150 * (5280/1) = 792k |
| Convert 325cm to ft using conversion factors. Note: 1cm = 2.54in. | 325cm * (1in/2.54cm) = 128in. 128in * (1ft/12in) = 10.7ft |
| SI Units | French: Systeme International d’Unites (International System of Units): a revised metric system now accepted by scientists throughout the world. |
| SI Units for: Mass, Length, Time, Temp, Electric Current, Amount of substance, Luminous Intensity. These seven units are known as the _____ | Mass: kg, Length: m, Time: s, Temperature: K, Electric Current: A (Ampere), Amount of substance: mol (Mole), Luminous Intensity: cd (candela). “Fundamental Units” |
| Derived units | Combinations of the seven base units. E.g. speed is a derived unit: m/s. Also Newton is a derived unit: kg*m/s^2 |
| The standard meter is based on… | Two quantities: the speed of light in a vacuum and the second. |
| Volume | The amount of space that the sample occupies. Extensive property |
| SI unit for volume. Is it used in chemistry? | The derived unit: m^3. In chemistry, the most important volume units are non-SI units, the liter (L) and the milliliter (mL) |
| Physicians and other medical practitioners measure body fluids in | Cubic decimeters (dm^3), which is equivalent to liters: 1L = 1dm^3 = 10^(-3)m^3 |
| Mass | Refers to the quantity of matter it contains. The SI unit of mass is the fundamental unit: kg. Extensive property. |
| Standard of measurement for kg? | It is the only base unit whose standard is a physical object: a platinum-iridium cylinder kept in France. |
| Weight | Depends on mass AND the strength of the local gravitational field pulling on it. |
| Density (d) | Mass/volume. Thus, with manipulation you can say volume = mass/density, etc. Intensive property |
| Extensive vs. Intensive properties | Extensive: those properties dependent on the amount of substance, e.g. mass and volume. Intensive: independent on the amount of substance, e.g. density. |
| SI Unit for density. What’s most often used in chemistry? | Kg/m^3, but in chemistry density is typically given in units of g/L (g/dm^3), or g/mL (g/cm^3). |
| Temperature | A measure of how hot or cold a substance is relative to another substance |
| Heat | The energy that flows between objects which are at different temperatures. |
| Temperature refers to… | The direction of the energy flow: when two objects at different temperatures touch, energy flows from the one with the higher temp to the one with the lower temp until they are equal. |
| Energy is a _____ property, temperature is a _____ property. | Extensive; intensive. |
| Does a boiling pot of water have the same temperature as a boiling cup of water? Do they have the same energy? | They have the same temperature (intensive property) but different energy level (extensive). |
| Thermometer | A devise that contains a fluid that expands when heated. It contracts when cooled. |
| Temperature scales more important to consider for chemistry | Celsius (°C, formally known as centigrade), Kelvin (K), and Fahrenheit (°F) |
| SI base unit of temperature | Kelvin (K), AKA the absolute scale |
| Celsius scale | Devised in the 18th century by the Swedish astronomer Anders Celsius, is based on changes in the physical state of water: 0°C is set at water’s freezing point, 100°C is set at water’s boiling point. |
| 0°C = _____ K | 0°C = 273.15K. Use this as the basis of conversion: K – 273.15 = °C. |
| Converting from °C to °F | °F = (9/5) °C + 32. °C = (°F-32)5/9. |
| Second. Standard? | SI unit for time. It is based on an atomic standard: microwave radiation absorbed by cesium atoms. |
| How does the cesium atomic clock—which the second is based on—work? | Rather than using the oscillations of a pendulum, the atomic clock measures the oscillations of microwave radiation absorbed by gaseous cesium atoms. 1 second is defined as ~9.19billion of these oscillations |
| Significant figures | The number of digits excluding zeros that are not measured but are used only to position the decimal point. General rule: exclude all leading zeros when there is a decimal point. Ignore trailing AND leading 0s when no dec. pt. |
| When measurements contain different numbers with different significant digits, which do you use? | Use the number that is least certain. E.g. if calculating density and the numbers are 3.8056g / 2.5mL = 1.5222, the answer should be 1.5 because it has the amount of sig figs that are least certain. |
| How many sig figs should the answer have when multiplying/dividing numbers? | It should have as many sig figs as the measurement with the fewest significant figures. E.g. 9.2 * 6.8 * .3744 = 23.4225. The answer should be written as 23 |
| How many sig figs should the answer have when adding/subtracting numbers? | The answer has the same number of decimal places as there are in the measurement with the fewest decimal places. |
| How do mechanical scales measure mass? | They compare the object’s unknown mass with known masses built into the balance, so the local gravitational fiels pulls equally on them. |
| How do electronic (analytical) balances measure mass? | They generate an electric field that counteracts the local gravitational field. The magnitude of the current needed to restore the pan to its zero position is then displayed as the object’s mass. |
| Precision | Reproducibility. Precision refers to how close the measurements in a series are to each other. |
| Accuracy | Refers to how close a measurement is to an actual value. |
| Systematic error | Produces values that are either all higher or all lower than the actual value. Such error is part of the experimental system, often caused by a faulty measuring device or by a consistent mistake in taking a reading. |
| Random error | In the absence of systematic error, produces values that are higher and lower than the actual value. Random error always occurs, but its size depends on the measurer’s skill and the instrument’s precision. |
| Precise measurements have a _____ random error | Low. |
| Accurate measurements have a _____ systematic error | Low, and generally a low random error as well |
| Calibration | Comparing a measuring device with a known standard. This helps to avoid systematic error. |
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