Elements, Compounds, and Reactions Lesson 3 Compounds Elements, Compounds, and Reactions

REVIEW EXAM QUESTIONS THE PERIODIC TABLE The diagram shows a section of the periodic table: Which element shown has the largest average atomic mass? A. Lithium B. Helium C. Calcium D. Oxygen

Essential Question:) How do atoms combine to form all types of matter? Vocabulary: Compound Ion Ionic bond Covalent bond

What are Compounds? -A compound is a substance made of two or more elements that are chemically joined in a specific combination. Examples: Citric Acid which is found in oranges, lemons, and other citrus fruits

Properties of Compounds Properties of compounds are usually different from the elements from which it is made. Compounds are formed from chemical reactions. Examples: Salt

How Do Atoms Bond? Atom bonds are formed by losing electrons, gaining electrons, and/or sharing electrons. Ion is an atom that is no longer electrically neutral because it has lost or gained electrons. An ionic bond occurs between metals and nonmetals when the substances react to gain or lose electrons in an attraction to become stable. A Covalent bond is a chemical bond formed when two atoms share valence electrons. It usually occurs between nonmetals.

What compounds make up common substances? Common substances are classified as either organic or inorganic. Organic substances all contain carbon and many are made by living things. Examples are the cells and tissues of your body. Inorganic substances do not come from living things and most of them do not contain carbon. Few carbon compounds that are inorganic substances are carbon dioxide and carbon monoxide; they are called inorganic compounds.

Organic v. Inorganic Substances

Essential Question Answer Atoms either gain or lose electrons (ionic bond)or share electrons ( covalent bond) in bonding with other atoms to form substances and become stable. 

LESSON 4: CHEMICAL REACTIONS AND ENERGY Elements, Compounds, and Reactions

READING GUIDE: ESSENTIAL QUESTION: Why do chemical reactions always involve a change in energy? VOCABULARY: Exothermic reaction Endothermic reactions Rate of reaction catalyst

Covalently Bonded Compounds A covalent compound is made when two or more nonmetal atoms bond by sharing valence electrons. The shared valence electrons between two nonmetal atoms is called a covalent bond. Covalent bonds are formed when two atoms begin sharing electrons. Covalent Compounds: Properties, Naming & Formation ... study.com/.../lesson/covalent-compounds-properties- naming-formation.htm...

Chemical Reactions and Energy An exothermic reaction is a chemical reaction that releases energy. This released energy comes from chemical bonds between atoms. In an exothermic reaction, the bonds in the reactants contain more energy than the bonds in the products Burning and rusting are exothermic reactions. Much of the energy you need to function comes from molecules called carbohydrates.

Exothermic Reaction http://study.com/academy/l esson/exothermic-reaction- definition-example-quiz.html

What are endothermic reactions? Chemical reactions that absorb energy are called endothermic reactions. Endothermic reactions require a constant supply of energy for the reaction to continue. In an endothermic reaction, the bonds of the reactants contain less energy than the bonds in the products. The energy absorbed during a chemical reaction comes from the environment surrounding the chemicals.

Endothermic Reaction

CHEMICAL REACTIONS Exothermic Reaction Endothermic Reaction

What can affect the rate of the reaction? The speed at which a chemical reaction occurs is called the rate of the reaction. Increasing the temperature or the concentration of reactants increases the rate of the chemical reaction. The exposed surface area of reactant particles also affect the rate of a chemical reaction. The larger the area that is exposed, the faster the reaction takes place. Increasing temperature causes the particles in a substance to move fast. This causes particles to collide more often.

The rate of a Chemical Reaction

What are catalysts? A substance that speed up a chemical reaction without being changed in the reaction is called a catalyst. In cars, catalytic converters change harmful substances into less harmful substances.

View of how a catalyst works

ESSENTIAL QUESTION ANSWER Energy is required to break the bonds so that new chemical bonds occur.

TEST QUESTION Debbie noticed that when whole coffee beans are finely ground, they take less time to undergo the chemical reactions and it makes the grounds change their flavor. Which is the best explanation for this? A. Smaller particles don’t taste good. B. Large particles don’t lose their flavor. C. Larger particles don’t undergo chemical reactions. D. The surface area of the coffee beans is increased