CHAPTER 12: MATTER Ms. Johnson Foundations

Objectives Matter is anything that has mass and occupies space. Matter can exist as a solid, liquid, or gas. Changes in matter may be physical or chemical. During a chemical change, new substances are formed. Elements are substances that cannot be broken down into simpler substances. Two or more elements can combine to form a compound. Atoms are composed of protons, neutrons, and electrons. Matter can neither be created nor destroyed in a chemical reaction. Energy can either be absorbed or released during a chemical change. Factors such as temperature and particle size influence the rate of a chemical reaction.

Vocabulary Matter Mass Volume Elements Atom Chemical bond Chemical reaction Mixture Physical properties Phases Melting Freezing Boiling/evaporation Condensation Melting point Freezing point Boiling point Physical change Chemical change Law of Conservation of Matter Rate

MATTER Chapter 12: Matter

Defining Matter Matter: anything that has mass and takes up space. Mass is the amount of material in an object The amount of space something takes up is its volume There are some things that have no matter. Ex. Light Rays- light is a form of energy and energy is not matter because it has no mass and no volume.

Elements Elements: the basic building blocks of matter. Represented by a symbol of one or two letters There are 110 known elements Less than half of these occur in nature All substances are made up of one or more elements. The smallest particle of an element is an atom. All atoms of one element are alike, but they differ from atoms of other elements. Ex. Hydrogen atoms and Oxygen atoms are not similar.

Atomic Structure All atoms are composed of subatomic particles: Protons, neutrons, electrons These particles differ in mass, charge, and location in an atom. Protons and neutrons have close masses, but electrons are lighter Protons and neutrons are found in the nucleus, electrons around the nucleus Protons (+ charge), neutrons (no charge), and electrons (- charge) The atoms of different elements differ in the number of protons in their nucleus. The number of protons is called the atomic number.

Compounds There are millions of difference substances known to scientists, but there are only 110 elements. How is that possible? Elements can combine to form new substances. A substance that is formed when two or more different elements combine is called a compound. Ex. the common substance water is a compound of hydrogen and oxygen combined. Compounds are represented by chemical formulas showing the proportions elements have combined in. Ex. H 2 Othere are two hydrogen combined with the one oxygen

Compounds Molecule: the smallest particle of a compound H 2 Oone oxygen molecule Atoms and molecules are extremely small. To put it in perspective, one teaspoonful of water contains about 175 sextillion water molecules. (17,500,0000,000,000,00 0,000,000)

Chemical Bonds Chemical Bond: a link formed between atoms in a molecule These bonds contain energy Sometimes this energy can be released in a chemical reaction Ex. burning wood is a chemical reaction that releases energy

Mixtures When two or more materials combine and do not form a new substance, a mixture has been formed. Ex. Salt Water Ex. Sand Ex. Air Ex. Blood Mixtures cannot be separated by a chemical formula. Mixtures can also be changed. Ex. NaCl is the same everywhere, but salt water can be changed based on how much water and salt is in the mixture.

Physical Properties Physical properties: properties that can be determined without changing the identity of a substance. Some examples of physical properties include: phase, color, odor, density, solubility, melting point, and boiling point.

Phases Different forms of matter are called phases. Solids: the molecules are close together, move very slow, and remain in a fixed, unchanging position. Has definite shape and definite volume Liquids: the molecules are farther apart and move faster than solids. The molecules can change position and flow past each other Has no definite shape and can take on the shape of its container Gases: the molecules are very far apart and move the fastest and they can move anywhere in a container Has no definite shape or volume, but can expand to fill a container

Phase Changes

CHANGES IN MATTER Chapter 12: Matter

Physical Changes A phase change, such as freezing or melting, does not produce any new substance. Physical Change: a change that does not result in the formation of any new substances. All phase changes are physical changes Ex. Water freezing. The molecules are still hydrogen and oxygen, nothing has changed but the state

Chemical Changes Ex. If you leave milk out. First it gets warm- this is a physical change. Then it turns sour- this is a chemical change because something new is produced. Chemical Change: a change that produces one or more new substances Caused by a chemical reaction Forming a compound always involves a chemical change. Chemical changes can be represented by chemical equations. Ex. C + O 2  CO 2 The starting materials are called reactants, and the results are called products.

Properties and Chemical Changes New substances that form from a chemical change have their own properties that differ from the original substances. Ex. Chlorine is a poisonous green gas When combined with sodium, they produce sodium chloride, table salt. This new substance has completely new properties. The atoms have rearranged to form new substances. The existing chemical bonds have been broken and new ones have been formed.

Conservation of Matter In a chemical change, no atoms are created or destroyed. Whatever is present beforehand is still there after, the atoms have just become arranged differently. Law of Conservation of Matter: states that matter cannot be created not destroyed in a chemical reaction. It can be changed from one form to another. It is important to account for all substances before and after a reaction, even ones that are not easy to weigh(like air).

Energy and Chemical Changes Energy is needed to start chemical reactions. (They don’t just happen). Energy can be provided in the form of heat, light, or electricity. Keep in mind not ALL chemical changes require energy. Ex. Iron rusting and silver tarnishing As a chemical reaction occurs, energy is either absorbed or released. Ex. burning a match releases energy in the form of heat and light Ex. cooking food absorbs heat energy

Energy and Chemical Changes Releasing Energy Chemical Changes That Release Energy Type of Energy Released Burning of woodLight, Heat Battery powering a flashlight Electricity Decomposing of organic matter Heat Absorbing Energy Chemical Changes That Absorb Energy Type of Energy Absorbed Cooking an eggHeat Researching a battery Electricity PhotosynthesisLight

Reversible Reactions Many physical changes can be reversed (melting of ice and refreezing) Most chemical changes, however, are very hard to reverse. Ex. you can’t unburn a match. But, some can be reversible. Ex. recharging a battery Reversing a chemical change usually requires much more energy than reversing a physical change does.

Rate of Reactions The souring of milk can happen whether left out of the fridge or left in the fridge. The only difference is that in the fridge, the reaction just takes a longer amount of time. An increase in temperature increases the rate (speed) of a reaction. Another factor is the particle size. The smaller the particles, the faster the reaction.

QUESTIONS? Chapter 12: Matter Homework: Pages 149, 150, 154, points