Page 101 - The Ontario Curriculum, Grades 9 and 10: Science, 2008 (revised)

friction. The force resisting the relative motion of two surfaces in contact.
gravitational force. The force of attraction be- tween all masses in the universe, especially the attraction of the earth’s mass to bodies situated within the earth’s gravitational field.
greenhouse gas. An atmospheric gas that allows solar radiation to pass through the atmosphere but absorbs the radiation that Earth emits back to space, thereby trapping heat and making the planet’s surface warmer. These gases include carbon dioxide, water vapour, methane, and the fluorocarbons.
group (chemistry). See periodic group. hydrosphere. The collective mass of water found on, under, and over the surface of the earth.
image. A reproduction of an object, such as may be produced by an optical device (e.g., by a lens or a mirror).
incandescence. A light omitted from a material because of the high temperature of that ma- terial (e.g., from a filament in an incandescent light bulb).
incident ray. A ray of light travelling from a source towards an object.
induction (of electric charge). The movement of electrons in a substance, caused by a nearby charged object without direct contact between the substance and the object.
insulator (electric). A solid, liquid, or gas that resists or blocks the flow of electricity (e.g., wood).
ion. An atom (or group of atoms) that has become charged because of an imbalance in the number of electrons and protons.
ionic compound. A compound that is held together by ionic bonds. It is composed of one or more positively charged ions and one or more nega- tively charged ions.
invasive species. A species that is introduced by human activity to an ecosystem not native to that species and that has an adverse effect on the ecosystem.
kilowatt. 1000 watts.
kilowatt-hour (kWh). A unit of work or energy equal to that expended by one kilowatt in one hour.
law of attraction. Particles with opposite charges attract one another.
law of conservation of mass. A fundamental law of chemical reactions that states that the total mass of the reactants in a chemical reaction is always equal to the total mass of the products.
law of repulsion. Particles with identical charges repel one another.
laws of reflection. The angle of incidence is equal to the angle of reflection. The incident, normal, and reflected rays all lie on the same plane.
light year (ly). A unit used to measure interstellar distance, equivalent to the distance travelled by light (at 300 000 km/s) in one year (approximately 9.5 trillion km).
limiting factor. An environmental factor that prevents an increase in the number and/or size of organisms in a population or in the distribu- tion of the population in an ecosystem.
lithosphere. The solid upper layer of Earth, con- sisting of the crust and upper mantle.
luminescence. The emission of light by a material or an object that has not been heated (e.g., fluo- rescence, phosphorescence).
magnetosphere. The region of space enclosed by a celestial object’s magnetic field.
magnification. The degree of enlargement of an optically or electronically produced image.
GLOSSARY
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