Unit 2: Matter - Review Leonard M. Fischer Plantation Middle School

What is Matter? Everything in the universe can basically be divided into one of two categories; matter or energy. Matter is anything that takes up space and has mass. Volume – is the amount of space something takes up. It is usually measured in cm 3. To calculate volume of a regular object, multiply length x width x height. To calculate volume of an irregular object, use the water displacement method. Remember that 1ml of water is equal to 1 cm 3, so no mathematical conversion is required. Mass – is the amount of matter in an object. It is measured using a balance. Weight Distinguished – Do not make the rookie mistake of confusing weight and mass. Weight is a measure of gravitational pull, and changes depending on the location of the object. Mass is a measure of how much matter is in an object and remains the same regardless of location.

Physical Properties Physical Properties – Characteristics of substances that can be changed or measured without changing the identity of the substance. Everyday Examples: Color, Shape, Size, Texture, Smell…. Other Important Physical Properties: Density – relationship between mass and volume. Tells you how tightly packed together the tiny atoms and molecules are in a sample of matter. Can be calculated by the formula D=M/V. Melting/Freezing/Boiling Point – The point at which a substance changes from one state to another. These are important physical properties that can help identify a liquid. Example: Alcohol and water are both clear liquids, but melt, freeze and boil at different temperatures. Solubility – The ability of one substance to dissolve in another. Example sugar in water. Electrical Conductivity – The ability of the substance to conduct (transfer) electricity. This is a common property of metals. Thermal Conductivity – The ability of the substance to conduct (transfer) heat. This is also a common property of metals. Malleability – The ability of a substance to be bent and pounded into thin sheets. Again, a property of most metals.

Chemical Properties Chemical Property – A substance’s ability to change into a new substance with different properties. Examples: Rusting, burning, reacting to give off heat or light. The substance doesn’t actually have to change. For example, not being able to burn or rust is a chemical property.

Physical Change Physical Change – A change of matter in form (physical appearance) only. Does not actually change the substance. Change of State – A change from a solid to a liquid or a gas is a change of state. This is always a physical change. Water is the same substance whether it is ice, liquid water, or water vapor. It is all still water. Other Examples: Cutting into smaller pieces, crumpling, dicing, slicing, etc.

Chemical Change Chemical Change – A change which results in the formation of a new substance. Signs of a Chemical Change: Production of heat (Exothermic Reaction) Taking in of heat (Endothermic Reaction) Creation of light (Chemoluminescent Reaction) Change of color Formation of a gas or solid Examples: Burning Reacting

Law of Conservation of Mass Law of Conservation of Mass – Matter is never created or destroyed, it just changes from one form to another. Basically, the universe is a giant recycling program. Example: Burn a piece of paper, and you have ash and smoke. The paper didn’t disappear. It turned into the ash and smoke. All the particles of matter, are still there. The atoms have just been scrambled and rearranged into new forms of matter. The total amount of matter is the same, both before and after the change.

States of Matter Particles in Motion – Remember that particles are always in motion. How much energy they have, and how much they can move, determines their state. Solid – Particles have a small amount of energy and are stuck vibrating in fixed locations. Thus, solids have a definite volume and a definite shape. Liquids – Particles have a bit more energy and are moving faster. Now, they can move past each other and move out of position. Therefore, liquids have a definite volume. But no definite shape. Gas – Particles have a lot of energy and can move rapidly out of their positions. Therefore, gasses have no fixed shape and no fixed volume. They will keep expanding away from each other. Changes of State – Occur when energy is added or removed. Temperature – A measure of the amount of kinetic energy in an object. (How much are the particles moving) Heat is the transfer of energy from a warmer object to a cooler object.

Pure Substances vs. Mixtures Pure Substances – One element, or more than one element chemically bonded together. Elements – Anything on the periodic table. (Ex: Gold, Silver, Carbon) Compounds – Combinations of elements chemically bonded together. (Ex: Water) Mixtures – More than one substance, NOT chemically bonded to each other. Can be separated by physical methods. Homogenous – Looks like only one substance, although it is not Solutions – Very small particles evenly spaced and not visible (Ex: Coffee, Sugar Water, Tea, Kool Aid) Heterogenous – A mixture where you can clearly see the different substances. (Ex: Trail Mix, Salsa) Suspensions – Big particles “suspended” in a liquid. Will settle to the bottom over time. (Ex: Vegetable Soup) Colloids – Mid sized particles floating in a fluid that do not settle out over time. (ex: Milk, Fog)