<p> Unit Exam 2017- Matter/Chemistry Study Guide 7th Grade Science – Miss Fox</p><p>Scientific Skills: Hypothesis - A tentative theory used to explain a set of facts. A hypothesis can lead to further investigation to test whether the hypothesis is valid (predication/educated guess). Variable - A factor in a scientific experiment that can vary. Controlled variable - A variable in an investigation or experiment that is held constant. Tested variable - A variable that is changed in a systematic way in an experiment or investigation in order to determine its effect. Observation - Any description or measurement gathered by the senses.  Qualitative Description - observation or analysis of a substance based on its qualities.  Quantitative Description - observation or analysis of a substance based on measurements. Physical Property - A characteristic of a substance or material, such as color, density, flexibility, hardness. Chemical Property - A specific result of a test with a chemical reagent. Chemical properties include pH, the production of a salt when an acid reacts with a metal, or a unique color change in a chemical reaction. </p><p>Chemistry - is the study of matter .</p><p>Matter/substance - Anything that has mass and takes up space. Matter is everything around you. Atoms and molecules are all composed of matter. Phase - A homogeneous (similar) state of matter, either solid, gas, or liquid.</p><p>Solid - A state of matter where the atoms or molecules are packed closely together and do not move freely. Liquid - A state of matter where the atoms or molecules are packed less closely than a solid but more closely than a gas and moving more than a solid. Gas - A state of matter where the atoms or molecules are farther apart than in a liquid and moving faster than a liquid.</p><p>Mass – The amount of matter in an object or system. We can find the mass of an object by using a triple beam balance. Weight - The vertical force exerted by a mass as a result of gravity. Volume - The amount of space matter takes up. Formula – V – l x h x w Density - The relationship between the mass and volume of a substance. The mass per unit volume, specifically grams per cubic centimeter, or grams per milliliter. Formula d = m/v *Know how to find the mass, volume and density of matter. Substances are classified into three groups - Elements, Compounds and Mixtures. Atom - The basic structural unit of matter; the smallest particle of an element, with bond together to form molecules.  The center of the atom is called the nucleus.  Protons and neutrons are found in the nucleus.  Neutrons have a neutral charge, also known as a charge of zero.  Protons always has a "+", or positive, charge.  Electrons always has a "-", or negative, charge.  Electrons are found in areas called shells. A shell is sometimes called an energy level.  Shells are areas that surround the center of an atom.  Each of those shells has a name (K, L, M...).  The atoms of different elements have different numbers of electrons, protons, and neutrons</p><p>Element - A collection of atoms of one type that cannot be separated. Oxygen, hydrogen, iron, and carbon are examples of elements. There are almost 120 types of elements, which combine to form compounds. </p><p>Chemical Formula - A shorthand notation to describe elements and compounds and their reactions. Each element is identified by one or two letters. For example, H represents hydrogen, Cl represents chlorine, and O represents oxygen.</p><p>Compound - A homogeneous (similar), pure substance composed of two or more different elements that are chemically combined. For example, H2O contains two atoms of hydrogen and one atom of oxygen chemically combined to produce a new substance with properties quite different from either hydrogen or oxygen. Compounds can be separated chemically. Mixture - A blending of two or more substances without chemical bonding or other chemical change, so that each substance keeps its own chemical properties and makeup. Mixtures can be separated physically. Know how to separate mixtures: Oil and vinegar – Let the mixture settle based on density and use a dropper to remove the top layer. Salt and iron shavings – Use a magnet to remove the metal from the salt.</p><p>Hazardous material - Any solid, liquid, or gas that can harm people, other living organisms, property, or the environment.</p><p>Corrosive - A substance that may dissolve metals, ruin clothing, or burn skin. Strong acids and bases are corrosive.</p><p>Flammable - Easily ignitable and capable of burning rapidly. Can serve as a fuel for a fire.</p><p>Toxic - Poisonous. The capability of a substance to cause harm to living systems, either in terms of a single dose (acute toxicity) or a sustained dose (chronic toxicity) over a period of time.</p>