Chapter 1 Concepts Flashcards
What is matter?
Matter is the physical material of the universe; it is anything that has mass and occupies space. (p.2)
What are the states of matter?
Gas, liquid, and solid
What is a gas?
Has no fixed volume or shape, conforms to the volume and shape of its container. Can be compressed to occupy a smaller volume or expanded into a larger one.
* Molecules are far apart and moving at high speeds colliding with each other and the sides of the container.
What is a liquid?
Has a distinct volume independent of its container but has no specific shape; assumes the shape of the portion of the container that it occupies. Cannot be compressed significantly.
* Molecules are packed closely but still move rapidly, sliding over each other (allowing the liquid to pour easily).
What is a solid?
Has both definite shape and a definite volume. Cannot be compressed significantly.
* Molecules are held tightly together in definite arrangements and can only wiggle slightly.
Law of the conservation of mass
Matter can be changed from one form into another, but the total amount of mass remains constant.
(The total mass of the universe is constant within measurable limits; whenever matter undergoes a change, the total mass of the products of the change is, within measurable limits, the same as the total mass of the reactants.)
What is a pure substance?
Matter that has distinct properties and a composition that does not vary from sample to sample.
(All substances are either elements or compounds.)
What is an element?
Cannot be decomposed into simpler substances. It is composed of only one kind of atom.
What is a compound?
Substances composed of two or more elements. They contain two or more kinds of atoms.
What is a mixture?
Combinations of two or more substances in which each substance retains its own chemical identity.
What is a heterogeneous mixture?
Do not have the same composition, properties, and appearance throughout. (like rocks and wood)
What is a homogeneous mixture?
Uniform throughout. (like air) Also called a “solution”.
What are physical properties of matter?
Can be observed without changing the identity and composition of the substance:
- Color
- Odor
- Density
- Melting point
- Boiling point
- Hardness
Explain chemical properties of matter
They describe the way a substance may change (react) to form other substances, such flammability (ability of substance to burn in presence of oxygen)
Describe physical changes of matter
A substance changes its physical appearance but not its composition (same substance before and after the change):
* evaporation of water (and all changes of states)
Describe chemical changes of matter
A substance is transformed into a chemically different substance. (also called a “chemical reaction”):
* when hydrogen burns in air
How to convert decimal number to scientific notation
- Aim is to produce a number between 1 and 10 times 10 to an exponent.
- When move a decimal to the left, the exponent increases; when moving the decimal to the right, the exponent decreases.
- Examples: 3450 = 3.45 X 10^3
.00345 = 3.45 X 10^-3
How to convert scientific notation to a decimal number
Positive exponent means move the decimal to the right; negative exponent means move the decimal to the left.
Define temperature
a measure of the average kinetic energy of the particles in a sample (the measure of the hotness or coldness of an object)
What is a “derived unit”?
When base SI units are used to derive the units of other quantities. (Speed is the ratio of distance traveled to elapsed time - m/s)
What is density (definition and equation)?
Density is the amount of mass in a unit of volume
mass
Density = ———
volume
Why are densities temperature-dependent?
Because most substances change volume when they are heated or cooled.
How is density expressed in SI units?
g/cm^3, or g/cc, or g/mL
What is the density of water at 25C?
1.00 g/cm^3
Define “precision”
Precision is a measure of how closely individual measurements agree with one another.
Define “accuracy”
Accuracy refers refers to how closely individual measurements agree with the correct, or “true”, value.
Define “standard deviation”
Precision of measurements is often expressed in terms of the standard deviation, which reflects how much the individual measurements differ from the average.
How to measure to significant digits
Measured quantities are generally reported in such a way that only the last digit is uncertain.
Example: If measuring a penny on a scale accurate to .0001 g, then the measurement would be reported to the 4th digit after the decimal, with the understanding that the last digit is uncertain.
Define “significant figures”
All digits of a measured quantity, including the last, uncertain one, are significant figures.
Significant Figures in Calculations - rule for addition/substraction
The result has the same number of decimal places as the measurement with the fewest decimal places.
Significant Figures in Calculations - rule for multiplication/division
The result contains the same number of significant figures as the measurement with the fewest significant figures.
