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Module 5. 5.01 Physical Changes. Physical properties include: Shape Size Melting Point Density. 5.01 Physical Changes. A physical change is any change in the property of matter that does not change the make up of the substance.
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5.01 Physical Changes • Physical properties include: • Shape • Size • Melting Point • Density
5.01 Physical Changes • A physical change is any change in the property of matter that does not change the make up of the substance. • In a physical change, the chemical make up of a substance does not change. The only thing that changes is a physical property such as: • Color • Shape • Phase (solid, liquid, or gas) • Size
5.02 States of Matter • The three main states of matter are: • Solid • Liquid • Gas • A sample of matter will have the same chemical composition whether it is a solid, liquid, or gas. The difference between the states of matter is the behavior and arrangement of the atoms or compounds
5.02 Advanced: The Fourth State of Matter • What do these three things have in common? • Image - Plasma TV: Each pixel in a plasma television screen is made up of three fluorescent lights: a red light, a green light and a blue light. Each fluorescent light contains mercury atoms that are in the plasma state. • Image - A Lightning Strike: Lightning is an example of plasma that is present at Earth’s surface. Temperatures in a lightning strike can reach 27,700 degrees Celsius. That high temperature changes the air from gas to plasma. • Image - The Sun: The matter that makes up the sun is in the plasma state due to its very high temperature. Scientists believe that the plasma state of the sun is what allows it to generate large amounts of energy in a very controlled manner. • They all contain atoms or compounds in the fourth state of matter, plasma!
5.02 Advanced: The Fourth State of Matter • You have learned about the three common states of matter: • Solid • Liquid • Gas • There is a fourth state of matter that is not as common on Earth but is the most common state of matter in the universe, plasma.
5.02 Advanced: The Fourth State of Matter • Plasma- is a collection of charged particles that respond strongly to electromagnetic fields, taking the form of gas-like clouds or ion beams.
5.02 Advanced: The Fourth State of Matter • Plasmas are found in: • Fluorescent lights. • Plasma TVs, which are made up of tiny fluorescent lights (in the pixels). • Lightning. • Auroras, which are an atmospheric phenomenon of bands of light sometimes seen in the sky at the polar regions. Examples include the Northern Lights and Southern Lights. • The sun and stars. • Nebulae. • Interstellar space.
5.03 Chemical Changes • A chemical change is a change one or more substances undergo when they become new or different substances. Another name for a chemical change is a chemical reaction. • Fireworks are an example of chemical change. The light, sound, and color are all signs that a chemical change is occurring
5.03 Chemical Changes • When a chemical change or reaction occurs: • The substances at the end of the reaction have different properties than the original substances. • The chemical bonds holding atoms together as compounds are broken. • New chemical bonds are formed, resulting in new chemical compounds.
5.03 Chemical Changes • Some easily observed changes strongly suggest that a chemical change has occurred. • Color change • Bubbling or fizzing • Light or heat production • Production of gases or solids • Odor production
5.03 Chemical Changes • Chemical changes occur on the molecular level, by breaking the bonds in chemical compounds and then forming new compounds. The amount of each type of atom is still the same at the end of the reaction, but their arrangement is different when the new bonds are formed.
5.04 Temperature and Chemical Change • Scientists use a thermometer to determine if a change was endothermic or exothermic. • If the thermometer shows an increase in temperature, the reaction gave off heat energy. This means the reaction was exothermic. • If the thermometer shows a decrease in temperature, the reaction took in heat from the surroundings. This means the reaction was endothermic.
Endothermic Vs. Exothermic • In a phase change, if the particles of matter are being pulled farther apart from each other, that will require energy. • Melting and boiling are endothermic processes; they require the addition of heat in order to occur. If the particles are becoming more condensed or coming closer together, energy will be given off. • Condensation and freezing are exothermic processes that give off heat as they occur.
5.06 Laws of Conservation of Mass and Energy • Ice cream melts • The same amount of matter is present before and after the melting, it is just in a different state. • Glass breaks • The same amount of glass is present; it is just in smaller pieces. If you measured the mass of all the little pieces of glass the total would equal the mass of the original piece of glass.
5.06 Laws of Conservation of Mass and Energy • An egg is cooked • The same amount of matter is present before and after cooking the egg. This is a chemical change. • Water evaporates • It may seem like the amount of matter decreases as the water evaporates, but it doesn’t. The same total amount of water molecules are still present, they are just present as a gas instead of a liquid.
5.06 Laws of Conservation of Mass and Energy • The law of conservation of mass -says that matter cannot be created or destroyed by ordinary chemical or physical changes. • This means: • The mass will be the same before and after the chemical or physical change • There are the same number of each type of atom before and after the change • The total mass of all components of a chemical reaction or physical change can be measured before and after the change to demonstrate that the mass is constant.
5.06 Laws of Conservation of Mass and Energy • Scientists believe that energy is conserved, like mass, during a physical or chemical change. The law of conservation of energy -says that energy can be converted from one form to another, but it cannot be created or destroyed in ordinary chemical or physical changes. • Energy can be more challenging for scientists to keep track of during a chemical reaction than mass. Mass is able to be measured on a balance before and after the change, but scientists must use more advanced techniques to measure the energy in a system.
5.06 Laws of Conservation of Mass and Energy • Plants • Plants convert energy from the sun to chemical energy that we can use in a process known as photosynthesis. This chemical energy is then available to us as food. • Dam • The power of the water retained by the dam is converted to mechanical and electrical energy as it flows through a dam.
5.06 Laws of Conservation of Mass and Energy • Fire • The chemical energy in compounds like wood, coal, and natural gas is converted to heat energy as combustion (burning) occurs. • Wind Turbine • The energy of wind is converted to mechanical and electrical energy as the wind turbine is turned.
5.06 Laws of Conservation of Mass and Energy-Review • This type of change breaks bonds and rearranges atoms to make new compounds. Chemical • The amount of energy before a reaction is ____ to the amount after the reaction. Equal • The law of conservation of ___ says that matter cannot be created or destroyed. Mass • This is a chemical change that occurs when wood or coal is burned. Combustion • Mass and energy are both ___ in chemical and physical changes. Conserved
5.06 Laws of Conservation of Mass and Energy-Review • Energy is ___ from one form to another, but is not created or destroyed in a chemical or physical change. Converted • This is a chemical change in which plants converts energy from the sun to chemical energy we can eat. Photosynthesis • The mass of a system can be ____on a balance both before and after a reaction to prove that mass was conserved. Measured • This can be converted from one form to another but cannot be created or destroyed by an ordinary chemical or physical change. Energy • This type of change does not alter the identity of a substance, but may change its phase or shape. Physical
Module 5 Review • Be sure to review: • The characteristics of chemical and physical changes. • The states of matter. • Endothermic and exothermic reactions. • The law of conservation of mass and energy. • The law of conservation of mass activity.
