Essay About Substances Change And Chemical Reactions

Chemistry Holt McDougal Chapter 2 Notes
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Section 1-Describe ways in which chemistry is part of your daily lives.                                                                                                                                                                                                The uniform I wear for school, the food I eat, and the air I breathe are all made up of chemicals. -Chemical – Any substance that has a definite composition. -A chemical is always made of the same stuff no matter where it comes from. Some chemicals, such as water and carbon dioxide, exist naturally. Others, such as polyethylene, are manufactured, and aluminum is taken from natural materials.-Chemical Reactions – The process by which one or more substances change to produce one or more different substances.-Examples of chemical reactions:                                                       Cooking foodTaking a pictureSwitching on a flashlightStriking a match-States of Matter – The physical forms of matter, which are solid, liquid, gas, and plasma.-What determines the properties of the matter?                                                                                                           l. The type and the arrangement of the matter. Solids have fixed volume and shape. The particles in a solid are tightly packed, usually in a regular pattern.Liquids have fixed volume but not a fixed shape. The particles in a liquid are close to each other with no regular arrangementGases have neither fixed shape and fixed shape. The particles in a gas are very far from each other with no regular arrangement. Plasma is different from a gas, because it is made up of groups of positively and negatively charged particles. PlasmaHas an indefinite shape and an indefinite volume.The common state of matter.A plasma is an ionized gas.A plasma is a very good conductor of electricity and is affected by magnetic fields.-Physical Changes – are changes in which the identity doesn’t change. However, the arrangement, location, and speed of particles that make up a substance may change. For example, cutting paper, boiling/melting water, crushing a can.-Chemical Changes – Chemical change is any change that results in the formation of new chemical substances. Chemical change involves making or breaking of bonds between atoms. Examples of a chemical change include rusting of iron, baking a cake, rotten food.-Reactants – The substances on the left side of an equation.-Product – The substances on the right side of an equation. -Chemical Reaction – A rearrangement of the atoms that make up the reactants or products. -Why doesn’t the mass change during a chemical reaction?                                                                                                                     Atoms aren’t destroyed nor created so the mass doesn’t change during a chemical reaction.-Evidences that a chemical change has occurredThe evolution of gas. (bubbles are formed)The formation of a precipitate (when two clear solutions are mixed and become cloudy)The release or absorption of energy. (a change of temperature or the giving off of light energy)A color change in the reaction system. (when 2 chemicals react and the color changes)Section ReviewWhat are 3 natural chemicals and 3 artificial chemicals we use in our everyday lives?                                                                                                                              Natural Chemicals: Glucose, Salt, WaterArtificial Chemicals: Drugs, Detergent, Paint     Describe how chemistry is part of your daily routine?In the morning we eat food so our bodies have to digest the food and break it down into simpler forms so that is a chemical reactionClassify the following things as solid, liquid or gas.                                                                                         Milk = Liquid, Helium = Gas, Granite = Solid, Oxygen = Gas, Steel = solid, Gasoline = liquid.Describe the motion of the particles in the 3 types of matter?Solids are uniform and close together, Liquids are more loose and slide past one another, Gas is spread out.How does physical change differ from chemical change?                                                                                   Physical changes are reversible while chemical changes cannot be reversed.Give 3 examples of physical changes.                                                                                                                                                                                            Cutting Paper, breaking a pencil, bending a metal fork.Give 3 examples of chemical changes.                                                                                                                      Burning paper, Rust, decay.Identify each of the following parts of the equation as product or reactant.                                                    Limestone = Reactant being broken down; Lime and Carbon Dioxide = Products of broken down limestone once heat is released.Sodium Salicylate is made from carbon dioxide and sodium peroxide. Identify what are the products and reactants?                                                                                                                                       Carbon Dioxide and Sodium Peroxide are the reactants and Sodium Salicylate is the product.List 4 signs that show a chemical change is occurring?                                                                                     When you see gas being released, light being released, 2 or more chemicals mix and combines, and heat being released.Explain why neither liquids or gases have permanent shapes?                                                                                           Liquids take the form of whatever container they’re in because the particles are loose and not uniform while gases are spread apart.Steam is sometimes used to melt ice is this a chemical or physical change?                                                          It is a physical change because steam is water becoming hot while ice melting can be reversed which is a physical property.Mass does not change in a chemical change is this also true with a physical change?                                   Yes, mass does not change even in Physical change because atoms aren’t destroyed nor created.In beaker A, water is heated, bubbles of gas form throughout the water, and the water level in the beaker slowly decreases. In beaker B, electrical energy is added to water, bubbles of gas appear on the ends of the wires in the water, and the water level in the beaker slowly decreases.                                                                                                                                                                     a. What signs of a change are visible in each situation?                                                                                                   b. What type of change is happening in each beaker? Explain your answer.                                                     A. Formation of bubbles and lowering of water level occurs in each beaker. B. In Beaker A, the change is physical, water turning to water vapor and evaporating causing the level to drop. In Beaker B, the change is chemical, water is broken down into H2 and O2 by electrolysis and the gasses disperse into the air causing the level to drop.Section 2-Matter – Anything that has mass and takes up space.-Volume – The space an object occupies. -How can the volume of an object be determined? (solids).                                                                                                                                                                The volume can be determined by multiplying the length, width, and height of the object. -Graduated Cylinders are often used in labs to measure the volume of liquids. -Mass – The quantity of matter contained in an object.