8th grade study guide-final exam-science

Solenoid
A coil of wire with an electric current in it.

electromagnet
a coil that has a soft iron core and that acts as a magnet when a electric current is in the coil.

electric motor
a device that converts electrical energy into mechanical energy.

exothermic reaction
a chemical reaction in which heat is released to the surroundings.

acid
any compund that increases the number of hydronium ions when dissolved in water.

base
any compound that increases the number of hydroxide ions when dissolved in water.

ionic bond
a bond that forms when electrons are transferred from one atom to another, which results in a positive ion and a negative ion.

covalent bond
a bond formed when atoms share one or more pairs of electrons.

metallic bond
a bond formed by the attraction between positively charged metal ions and the electrons around them.

proton
a subatomic particle that has a positive charge and that is located in the nucleus of an atom.

neutron
a subatomic particle that has no charge and that is found in the nucleus of an atom.

electron
a subatomic particle that has a negative charge.

solid
the state of matter in which the volume and shape of a substance are fixed.

liquid
the state of matter that has a definite volume but not a definite shape.

gas
a form of matter that does not have a definite volume or shape.

mass
a measure of the amount of matter in an object.

weight
a measure of the gravitational force exerted on an object; its value can change with the location of the object in the universe.

classification
the division of organisms into groups, or classes, based on specific characteristics.

dichotomous key
an aid that is used to identify organisms and that consists of the answers to a series of questions.

taxonomy
the science of describing, naming, and classifying organisms.

paleontology
the scientific study of fossils.

mold
a mark of cavity made in a sedimentary surface by a shell or other body.

cast
a type of fossil that forms when sediments fill in the cavity left by a decomposed organism.