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a representation of an object or event that can be studied to understand the real object or event


the application of science for practical uses. Advances in science depend on this:


observing, studying, and experimenting to find the nature of things

critical thinking

when you approach a problem by asking questions, making observations, and using logic to make a decision

scientific methods

general ways to help organize your thinking about questions


a process in nature that can be tested by repeated experiments


a factor that changes in an experiment in order to test a hypothesis


a measure of the amount of matter in an object

dependent variable

the observed result of the variable being manipulated or changed


a description of how close a measurement is to the true value of the quantity measured

independent variable

the variable representing the value being manipulated or changed


the exactness of a measurement


an explanation of how a natural process works


a measure of the gravitational force exertedd on an object


a substance made up of atoms of two or more different elements joined by chemical bonds


the physical form of a substance

melting point

the temperature and pressure at which a solid becomes a liquid

chemical change

a change that occurs when one or more substances change into entirely new substances with different properties


anything that has mass and takes up space


a substance that cannot be separated or broken down into simpler substances by chemical means


a combination of two or more substances that are not chemically combined


the ratio of the mass of a substance to the volume of the substance

boiling point

the temperature and pressure at which a liquid becomes a gas


the smallest unit of an element that maintains the chemical properties of that element

physical properties

characteristics tha can be observed without changing the identity of the substance

physical change

a change of matter from one form to another without a change in chemical properties


when oxygen and hydrogen atoms combine to form a molecule


a nonsolid state of matter in which the atoms or molecules are free to move past each other

law of conservation of mass

the idea that mass cannot be created or destroyed

hydraulic devices

the use of liquids to transmit pressure form one point to another


the amount of force exerted per unit area of a surface


a state of matter that consists of free-moving ions and electrons that does not have definite shape or volume

gas laws

the laws that state the mathematical relationships between the volume, temperature, pressure, and quantity of as

condensation point

the temperature at which a gas becomes a liquid


the resistance of a gas or liquid to flow

buoyant force

the upward force that keeps an object immersed in or floating on a fluid


the capacity to do work


the SI unit for pressure


a measure of how hot or cold something is; specifically, a measure of the average kinetic energy of the particles in an object

kinetic energy

the energy of motion


negatively charged particles inside the atom


an atom's central region, which is made up of protons and neutrons

law of definite proportions

this states that a chemical compound always contains the same elemetns in exactly the same proportions by weight or mass. an example of this is water.


a region in an atom where there is a high probability of finding electrons

protons and neutrons

two subatomic particles that are almost identical in size and mass

ground state

the lowest state of energy of an electron


electrons gain energy by absorbing a particle of light called an ___.

electric force

positive and negative charges attract each other with a force known as ___.


Which orbital is sphere-shaped?


a charged atom

mass number

the sum of the number of protons and neutrons in the nucleus of an atom


an atom that has the same number of protons but a defferent number of neutrons relative to other atoms of the same element

molar mass

the mass in grams of one mole of a substance

atomic number

the number of protons in the nucleus of an atom


in the modern atomic theory, electorns can be found only in certain ____ levels.

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