Science Midterm Review Flashcards

Significant Figures

All non-zero digits and any zeros that are contained between non-zero digits. Leading zeros don't count, and trailing zeros may not count if there is no decimal point.

Scientific Notation

A shorter way to write a long number. The decimal is placed after the first significant figure, and the power of 10 indicates how many places the decimal moved (positive for left, negative for right).

Matter

Anything that has mass and takes up space.

Atom

The smallest particle of an element.

Element

A substance composed of atoms having an identical number of protons in each nucleus. Elements cannot be reduced to simpler substances by normal chemical means.

Compound

A pure, homogeneous substance consisting of atoms or ions of two or more different elements in definite proportions that cannot be separated by physical means. A compound usually has properties unlike those of its constituent elements.

Mixture

A composition of two or more substances that are not chemically combined with each other and are capable of being separated.

Pure Substance

A sample of matter, either an element or a compound, that consists of only one component with definite physical and chemical properties and a definite composition.

Chemical Change

A process where bonds are broken and new bonds are formed between different atoms.

Physical Change

A usually reversible change in the physical properties of a substance, such as size or shape.

Gas

A substance having no definite shape and no definite volume. The molecules are spread out and free to move.

Liquid

A substance having a definite volume, but no definite shape. The intermolecular forces hold these atoms or molecules loosely together but do not force them into a rigid structure, allowing liquids the ability to flow.

Solid

A substance having a definite shape and definite volume. The atoms or molecules are held in a rigid structure. Although they are free to vibrate, they cannot move around.

Plasma

Gases that have been so energized that their atoms have been stripped of some or all electrons.

Pressure

The force exerted on a surface per unit area.

Volume

The amount of space that a substance or object occupies.

Mixtures

A mix of elements and compounds that are not chemically bonded. Can be heterogeneous (arrangement of particles is not uniform) or homogeneous (arrangement of particles is uniform).

Pure Substances

Can be elements (singular atoms) or compounds (chemically bonded elements).

Volume

For a cube/rectangular prism, it is calculated as length x width x height. For irregularly shaped objects, the water displacement method is used.

Density

The mass divided by the volume.

Phase Changes

Melting (solid to liquid), freezing (liquid to solid), vaporization (liquid to gas), condensation (gas to liquid), sublimation (solid to gas), deposition (gas to solid).

Kinetic Energy

The energy of an object because of motion.

Temperature

Measures the average kinetic energy of the particles of an object or substance. Measured in degrees Celsius or Kelvins.

Heat

The flow of energy from warmer places to cooler places due to a difference in temperature.

Thermal Equilibrium

When heat flows from a higher temperature object to a lower temperature object until they are the same temperature.

Heat Transfer

Can occur through conduction (transfer of heat energy between materials in direct contact), convection (transfer of heat energy by the mass movement of fluids containing heated particles), or radiation (transfer of heat energy through electromagnetic waves).

Endothermic

Energy going into the system.

Exothermic

Energy going out of the system.

Specific Heat

The energy needed to raise the temperature of a substance. Measured in joules per gram per degree Celsius (J/g°C) or calories per gram per degree Celsius (cal/g°C).

Boyle's Law

The volume of a given mass of gas varies inversely with the pressure when the temperature is kept constant.

Charles's Law

The volume of a given mass of gas varies directly with the temperature of the gas when the pressure is kept constant.

Gay-Lussac's Law

The temperature of gas varies directly with the pressure when the volume is kept constant.

Atoms

Consist of electrons (negative charge), protons (positive charge), and neutrons (neutral/no charge). Isotopes have different numbers of neutrons, and ions have a charge. Average atomic mass is the number of protons plus neutrons, and mass number is the average atomic mass rounded to the nearest whole number.

Periodic Table

Consists of 18 groups and 7 periods. Elements in the same group have the same properties and the same number of valence electrons, while