Chem Quiz 1

• All matter in the universe exists in one of three fundamental states: solid, liquid, or gas.
• 2.54 cm = 1 inch
• 1 mL = 1 cm3
• 1 pound (lb) = 454 grams
• Matter is anything that occupies space and has mass.
• An element is a substance that cannot be broken down into simpler substances.
• An atom is The smallest identifiable unit of an element.
• A compound is a substance composed of two or more elements in fixed, definite proportions.
• A chemical formula is a way to represent a compound. At a minimum, the chemical formula indicates the elements present in the compound and the relative number of atoms of each element.
• A reactant is an initial substance in a chemical reaction, represented on the left side of a chemical equation.
• A product is a final substance produced in a chemical reaction, represented on the right side of a chemical equation.
• An observation is often the first step in the scientific method. An observation must measure or describe something about the physical world.
• A hypothesis is a theory or law before it has become well established; a tentative explanation for an observation or a scientific problem that can be tested by further investigation.
• A theory is a proposed explanation for observations and laws. A theory presents a model of how nature works and predicts behavior that extends well beyond the observations and laws from which it was formed.
• A heterogeneous mixture is a mixture of two or more substances that are not chemically combined. A mixture, such as oil and water, that has two or more regions with different compositions.
• A homogeneous mixture is a mixture of two or more substances that are not chemically combined. A mixture, such as salt water, that has the same composition throughout.
• Exact numbers have an infinite number or significant digits.
• A measurement is a collection of quantitative or numerical data that describes a property of an object or event.
• SI units are the most convenient system for science measurements, based on the metric system—the standard units agreed on by scientists worldwide.
• Significant figures are the non–place-holding digits in a reported measurement; they represent the precision of a measured quantity.
• Mass is a measure of the quantity of matter within an object.
• Volume is a measure of space. Any unit of length, when cubed, becomes a unit of volume.
• Density is the measure of how much “stuff” is in a given amount of space.
• The density formula is mass divided by volume (density = m/V).
• Concentration is the ratio between two quantities, usually expressed as grams per liter (g/L) or milligrams per liter (mg/L).
• Conversion factor is a factor used to convert between two separate units; a conversion factor is constructed from any two quantities known to be equivalent.
• Unit analysis is used to convert from one set of units to another.
• Endothermic: (of a reaction or process) accompanied by or requiring the absorption of heat.
• Exothermic: (of a reaction or process) accompanied by the release of heat.
• Compound: A substance composed of two or more elements in fixed, definite proportions; a mixture.
• Solution: A homogeneous mixture of two or more substances.
• Joule: The SI-derived unit used to measure energy or work.
• Kilojoule: One thousand joules.
• Terajoule: One trillion joules.
• Pure Substance: A substance composed of only one type of atom or molecule.
• Specific Heat Capacity: The amount of energy needed to raise the temperature of 1kg of a substance by 1 degree.
• Q=mcΔT. (energy change) = mass x specific heat capacity x temperature change
• Physical Change: A change that does not involve forming or breaking down new substances. A change in which matter does not change its composition, even though its appearance might change.
• Chemical Change: A process whereby atoms are rearranged into different compounds with different properties from those of the original reactants.
• Chemical property: A characteristic of a substance that is caused by the presence of chemicals in it. A property that a substance can display only through changing its composition.