Ch. 1 Flashcards
Physical changes
Alters only the state or appearance of a substance but not it’s chemical composition.
Ex: when water boils, it changes from a liquid to a gas, but both are composed of water molecules.
Chemical changes
Alters molecular composition (chemical structure) of a substance.
During so atoms rearrange, transforming the original substances into a different substance.
Ex: rusting of iron. Iron atoms combine with oxygen molecules from air to form iron(ll) oxide, the orange-coloured substance we call rust.
Physical property
A property that a substance displays without changing its chemical composition.
Include— odour, taste, colour, appearance, melting point, boiling point, and density.
Ex: smell of gasoline— doesn’t change comp when it exhibits its odour.
Chemical property
A property that a substance displays only by changing its composition via a chemical reaction.
Includes— corrosiveness, flammability, acidity, toxicity, etc
Ex: combustibility of gasoline, changes it composition when it burns, turning into completely new substances (primarily carbon dioxide and oxygen).
Law of conservation
law of conservation of energy, energy is neither created nor destroyed.
The standard units
Quantity Unit Symbol
Length metre m
Mass kilogram kg
Time second s
Temperature kelvin K
Amount of substance mole mol
Electric current ampere A
Luminous intensity candela cd
SI prefixes
Prefix Symbol Multiplier
exa E 1 000 000 000 000 000 000 1018
peta P 1 000 000 000 000 000 1015
tera T 1 000 000 000 000 1012
giga G 1 000 000 000 109
mega M 1 000 000 106
kilo k 1000 103
hecto h 100 102
deca da 10 101
deci d 0.1 10–1
centi c 0.01 10–2
milli m 0.001 10–3
micro μ 0.000 001 10–6
nano n 0.000 000 001 10–9
pico p 0.000 000 000 001 10–12
femto f 0.000 000 000 000 001 10–15
Derived units
Derived units are either combinations of different units or multiples of units of the same type. For example speed in kilometres per hour.
Commonly derived units
Quantity Unit Name Symbol
density kilogram per cubic metre kg m−3kg m−3
gram per cubic centimetre g cm−3g cm−3
gram per millilitre g mL−1g mL−1
speed metre per second m s−1m s−1
kilometre per hour km h−1km h−1
volume cubic centimetre, millilitre cm3=mLcm3=mL
decimetre cubed, litre dm3=Ldm3=L
cubic metre, kilolitre m3=kL
Volume
The measure of space is referred to as volume. Any unit of length, when cubed (raised to the third power), becomes a unit of volume. Thus, the cubic metre (m3) and cubic centimetre (cm3) are units of volume.
Density
The density (d) of a substance is the ratio of its mass (m) to its volume (V): The density of a substance also depends on its temperature. Density is an example of an intensive property. is a characteristic physical property of materials and differs from one substance to another
Intensive property
one that is independent of the amount of the substance. The density of aluminum, for example, is the same whether you have an ounce or a tonne. Intensive properties are often used to identify substances because these properties depend only on the type of substance, not on the amount of it.
Extensive property
one that depends on the amount of the substance.
Significant figure rules
1.All nonzero digits are significant
2.Zeros between nonzero digits are significant.
3.Zeros to the left of the first nonzero digit are not significant. They only serve to locate the decimal point
4.Zeros at the end of a number are categorized as follows:
a.Zeros after a decimal point are always significant.
b.Zeros before a decimal point and after a nonzero number are always significant.
c.Zeros before an implied decimal point are ambiguous and scientific notation should be used.
Exact numbers
Exact numbers have no uncertainty, and thus do not limit the number of significant figures in any calculation. We can regard an exact number as having an unlimited number of significant figures.
Rules for calculations
In multiplication or division, the result carries the same number of significant figures as the factor with the fewest significant figures.
In addition or subtraction, the result carries the same number of decimal places as the quantity with the fewest decimal places
When computing the logarithm of a number, the result has the same number of significant figures after the decimal point (called the mantissa) as there are significant figures in the number whose logarithm is being calculated. The digits before the decimal place in the answer represent the order of magnitude.
When computing the antilogarithm (the inverse of the logarithm), the number of significant figures in the result is the same as the number of significant digits after the decimal (the mantissa). The number before the decimal place represents the order of magnitude.
Rules for rounding
When rounding to the correct number of significant figures, round down if the last (or rightmost) digit dropped is four or less; round up if the last (or rightmost) digit dropped is five or more. To avoid rounding errors in multistep calculations, round only the final answer—do not round intermediate steps
Accuracy and Precision
Accuracy refers to how close the measured value is to the actual value. Precision refers to how close a series of measurements are to one another or how reproducible they are. A series of measurements can be precise (close to one another in value, and reproducible) but not accurate (not close to the true value)
Random error
error that has equal probability of being too high or too low. Almost all measurements have some degree of random error. Random error can, with enough trials, average itself out.
Systematic error
error that tends toward being either too high or too low. Systematic error does not average out with repeated trials. For instance, if a balance is not properly calibrated, it may systematically read too high or too low.
General problem-solving strategy
• Identify the starting point (the given information)
• Identify the end point (what you must find).
• Devise a way to get from the starting point to the end point using what is given as well as what you already know or can look up. (We call this the conceptual plan.) Given to conceptual plan to find
- Sort. Begin by sorting the information in the problem. Given information is the basic data provided by the problem—often one or more numbers with their associated units. Find indicates what information you will need for your answer.
- Strategize. This is usually the hardest part of solving a problem. In this process, you must develop a conceptual plan—a series of steps that will get you from the given information to the information you are trying to find. Each arrow in a conceptual plan represents a computational step. On the left side of the arrow is the quantity you had before the step, on the right side of the arrow is the quantity you will have after the step, and below the arrow is the information you need to get from one to the other—the relationship between the quantities. Usually, however, you will need other information—which may include physical constants, formulas, or conversion factors This information comes from what you have learned or can look up in the chapter or in tables within the text. In some cases, you may get stuck at the strategize step. If you cannot figure out how to get from the given information to the information you are asked to find, you might try working backward. For example, you may want to look at the units of the quantity you are trying to find and try to
- Solve. This is the easiest part of solving a problem. Once you set up the problem properly and devise a conceptual plan, you simply follow the plan to solve the problem. Carry out any mathematical operations (paying attention to the rules for significant figures in calculations) and cancel units as needed.
- Check. This is the step beginning students most often overlook. Experienced problem solvers always ask, Does this answer make sense? Are the units correct? Is the number of significant figures correct? When solving multistep problems, errors easily creep into the solution. You can catch most of these errors by simply checking the answer, and considering the physical meaning of your result.
