Matter Atoms Energy

Matter/Atoms/Energy ➔ Matter is anything that has mass and takes up space (has volume) ➔ Matter is made up of atoms. The atom is the smallest unit of matter ➔ There are four states of matter: solid, liquid, gas, and plasma. ➔ Solids, liquids, and gases are all made of tiny particles, including atoms. The behavior of the particles differs between these three states of matter ➔ Solid ◆ Particles are tightly packed in a fixed pattern. They also vibrate, but they generally don’t move much from the original place. ◆ Has a definite shape and a definite volume ◆ Not compressible ◆ Does not flow easily ◆ Examples: Gold, Cars, Books ➔ Liquid ◆ Particles are close together but arranged randomly. They also vibrate, moving around and sliding past one another. ● The particles in liquids have more energy than the particles in solid, meaning they move more ◆ Takes the shape of the container but has a definite volume ◆ Not compressible ◆ Flows Easily ◆ Examples: Water, Milk, Mercury ➔ Gas ◆ Particles are randomly arranged, far apart, and often collide; they are separated and have no pattern. The particles vibrate and move very quickly/have the most energy compared to solids and liquids. ◆ Takes the shape of the container and fills the volume of the container ◆ Compressible ◆ Flows Easily ◆ Examples: Helium (inflates balloons) and Oxygen (the gas we breathe in) ➔ Plasma ◆ Similarly to gases, plasma does not have definite shape or volume ◆ Unlike gases, plasma produce magnetic fields; they conduct electricity ◆ Examples: Lightning and Fluorescent Lights ➔ A solid turns into liquid due to melting ➔ A liquid turns into gas due to evaporation ➔ A gas turns into liquid due to condensation ➔ A liquid turns into solid due to freezing ➔ Pure Substances (Elements & Compounds) ◆ Elements ● Contain one type of atom ● Each element has a unique set of chemical and physical properties ● They are represented by chemical symbols ○ “H” represents Hydrogen ○ “Ca” represents Calcium ● Elements cannot be broken down into simpler sections by physical or chemical means ◆ Compounds ● Composed of two or more different atoms joined by chemical bonds ● Made of elements in a specific ratio that is always the same ○ Salt is always NaCl ● All compounds have a chemical formula ○ NaCl is a chemical formula ● Compounds can be separated by chemical means but not physical means Note: A binary compound is specifically made from two different elements. ➔ Mixtures ◆ A combination of two or more pure substances that are not chemically combined ● This means mixtures can be separated physically and they are held together by physical forces, not chemical forces ◆ There is no chemical change in a mixture since it is reversible ◆ Each item in a mixture retains its original properties ● For example, a salad is a mixture. The dressing retains its properties, the lettuce retains its properties, etc. ◆ There are two main types of mixtures ● Homogeneous – molecules are mixed up in an even distribution ○ “Homo” means same, meaning the entire mixture looks the “same” ○ Coffee with milk and sugar thoroughly mixed into it would be homogeneous since you cannot see the milk and sugar after they are stirred in; you cannot distinguish the different ingredients ● Heterogeneous – molecules are not mixed up in an even distribution ○ “Hetero” means different, meaning parts of the mixture look different ○ Salad is a heterogeneous mixture since all the parts of it look different; you can clearly identify its different components, such as the lettuce, tomatoes, dressing, cucumbers, etc ➔ Compounds vs. Mixtures ◆ Compounds are composed in definite proportions ● H2O (water) always has two hydrogen atoms and one oxygen atom ◆ Mixtures are not composed in definite proportions ● You could make a salad with 75% lettuce and 25% dressing, or a salad with 90% lettuce and 10% dressing ➔ Examples ◆ A collection of rocks is a…mixture ◆ Copper (Cu) is an…element ◆ Jelly beans are a…mixture ◆ Table sugar (C12H22O11) is a…compound ◆ Tea is a…mixture ◆ Salt (NaCl) is a…compound ◆ Neon gas (Ne) is an…element ◆ Orangeade is a…mixture ◆ Sand is a…mixture ➔ Physical vs. Chemical Properties ◆ Physical Properties ● Observed with the five senses ● Determined without destroying matter (can be observed without changing the substance’s identity) ● Examples ○ Color, Odor, Taste ○ Opacity ○ Length ○ Volume ○ Boiling/Melting Point ○ Softness/Hardness ◆ Chemical Properties ● Only observed during a chemical reaction ○ Matter will be changed into a new substance after the reaction ● Indicates how a substance reacts with something else ● Examples ○ Acidity ○ Reactivity (e.g. reacts with certain bases, reacts with metals, etc) ○ Flammability ○ Toxicity ○ Tarnishes ○ Decomposes when heated ◆ Examples of Physical vs. Chemical Properties ● Blue color (physical) ● Density (physical) ● Reacts with water (chemical) ● Hard (physical) ● Supports combustion (chemical) ● Sour taste (physical) ● Burns in the air (chemical) ➔ Changes in Matter (Physical vs Chemical Changes) ◆ Chemical Change ● Also known as a chemical reaction ● Turns one set of reactants into new products by changing the composition and arrangement of the atoms and molecules ● Reactants → Products ○ A new substance is formed ● A change in the physical and chemical properties occurs ● Not reversible ◆ Physical Change ● Only changes the appearance (size, shape, or state), not the composition ● No new substance is formed ○ Substances retain their original properties ● Often reversible ◆ Examples of Chemical vs. Physical Changes ● Cutting hair (physical change) ● Alcohol evaporating (physical change) ○ Evaporation is liquid to gas ○ All changes in states of matter are physical changes because they are reversible ● Iron rusts (chemical change) ● Silver tarnishes (chemical change) ● Salt (NaCl) dissolves in water (physical change) ● An apple is cut (physical change) ● Milk sours (chemical change) ➔ Law of Conservation of Mass ◆ Matter cannot be created or destroyed ◆ The total mass of the reactants must equal the total mass of the products ➔ Atoms ◆ An atom contains smaller particles called subatomic particles ◆ The subatomic particles are protons (positive charge), electrons (negative charge), and neutrons (no charge) ◆ An atom contains a tiny nucleus with electrons surrounding it ● The protons and neutrons, which have about the same mass, are located inside the nucleus ● Electrons orbit the nucleus in orbitals/shells, and they have a negligible mass ○ Each orbital/shell can hold a different number of electrons ○ The first shell can hold a maximum of two electrons and the second shell can hold a maximum of eight electrons ○ The outermost shell of an atom is known as the valence shell ◆ The atoms in the valence shell are known as valence electrons ◆ The number of electrons in an atom’s valence shell determines how reactive the element is as well as its properties ◆ Most elements need eight electrons in their outermost shell (valence shell) to be stable ● Since protons are positively charged and electrons are negatively charged, they are attracted to each other ➔ Energy ◆ Energy is the ability to do work ◆ Work is the result of a force acting on a distance ◆ Energy is also conserved according to the Law of Conservation of Energy ● Energy cannot be created or destroyed; it can only be transformed from one form to another ◆ Exothermic Reactions ● Reactions that release energy (heat), making the system become more stable ● The temperature of the surroundings is increased ◆ Endothermic Reactions ● Reactions that absorb energy (heat) ● The temperature of the surroundings is decreased ◆ Activation energy is the energy needed to get the reaction started; it is required for the energy level of the reactants to change into the energy level of the products ◆ Activation energy is needed for absorbing energy and releasing energy ● This means it is needed for endothermic reactions and exothermic reactions ● As shown in the graph below, endothermic reactions require more activation energy to start the reaction compared to exothermic ○ This is because the reactants in an endothermic reaction have less energy than the products will have ○ The reactants need to absorb more energy in order to reach a higher energy state, requiring more activation energy ➔ Examples ◆ Photosynthesis is an endothermic reaction because it requires sunlight as energy input; thus, the amount of energy increases ◆ Combustion (the process of burning something) is an exothermic reaction because it releases heat and light energy