Chemistry Study Guide (Mrs. Brown)

Balance the Equation ___AI+ ___O2 --> ___AI2+O3

4, 3, and 2

Electron

- Negatively Charged (-) a particle with an electric charge (-e) found inside of atoms but outside the nucleus - electrons take up the region outside the nucleus in a region called the electron cloud or orbitals. - electrons are bound to the nucleus by the attractive force between electrons (negative charges) and neutrons (positive charges)

Chemical reaction

- a process that rearranges chemical bonds to create new substance - no new atoms are created

Compound

- a substance whose smallest particles include more than one element chemically bonded together. - an example; water is a compound of hydrogen and oxygen atoms bonded together. - it is different from a mixture since a mixtures are two or more elements that are NOT chemical bonded. - Most of the time when elements compound, most of the properties of the original elements are gone.

Chemical equation

- an equation of chemical formulas that shows the exact numbers of atoms and compounds in a chemical reaction

physical properties

- characteristics of matter that can be seen through direct observation such as density, melting point and boiling point. -Physical properties include color, texture, density, brittleness, and state (solid, liquid, gas). Melting point, boiling point, and specific heat are also physical properties. - Physical changes, such as melting, boiling, or bending are sometimes reversible, and no new substances are formed.

Chemical properties

- characteristics of matter that can only be observed when one substance changes into a different substance, such as iron into rust - Any change that transforms one substance into a different substance is called a chemical change. -Chemical changes are not easily reversible.

Physical change

- during a physical change, a substance changes its form but remains the same substance.

Chemical Formula

- identifies the number and element of each type of atom in a compound. -An example, the chemical formula Fe2O3 is for a cp, pound with iron (Fe) and oxygen (O)in a ration of 2 iron atoms for every 3 oxygen atoms.

Conservation of mass

- the mass of the reactants equals the mass of the products

Atomic number

- the number of protons in the nucleus. The atomic number determines what element the atom represent. - Atoms of the same element always have the same number of protons in the nucleus - because everything in nature are always (or trying to be) neutral, the number of proton and electron are the same. -

Molecular Structure

- the properties of a compound depend much more on the exact composition and structure of its molecule than on the elements of which it is made. - If (A) molecule has the same elements as (B) molecule, but their elements are arrange differently. This two molecule will be totally different.

Chemical change

- turns one or more substances into different substance that usually have different properties.

Evidence of a chemical reaction

-Gas Bubbles, Heat The following can indicate that a chemical change has taken place, although this evidence is not conclusive: Change of odor. Change of color (for example, silver to reddish-brown when iron rusts). Change in temperature or energy, such as the production (exothermic) or loss (endothermic) of heat.

Electric charge

-Two different kinds of electric charge, positive and negative - An object with excess positive charge strongly attracts negative charge until the object becomes neutral again.

Ionic bond

-a bond that transfers an electron from one atom to another resulting in attraction between oppositely charged ions. - an example; sodium and chlorine form an ionic bond. By losing an election, the sodium atom becomes a sodium ion with a charge of +1. By gaining an electron, the chlorine atom becomes a chloride ion with a charge of -1. The positive sodium ion is attracted to the negative chloride ion.

Valance electrons

-electrons in the highest unfilled energy level of an atom -these electrons participate in chemical bonds. -valence electrons is like the outer "skin" of an atom. -eight is a preferred number because 8 electrons are a complete energy level - a example, oxygen has 6 valence electrons, to get to 8, oxygen needs to add two electrons. Oxygen forms chemical bonds that provide these two extra electrons. 2 hydrogen could bond with oxygen, since 1 hydrogen has 1 extra electrons. These two extra electron can pair up with oxygen who is missing two.

Chemical vs. Physical change

A physical property is observed with the senses and can be determined without destroying the object. (Ex. Density, Melting Point, Hardness) A chemical property indicates how a substance reacts with something else. (Ex. Flammability, Sour Taste, Reacts with water to form a gas)

What type of equation is this? A + B --> AB

Addition Also known as Synthesis

Molecule structure vs. Chemical Formula

Although some chemical formulas are the same, it does not mean that they are the same substance. For example, Glucose and Fructose have the same chemical formula (Formula: C6H12O6), but have different molecule structures, which makes them different.

Evidence of a Chemical Change

Bubbles/ Gas formation- Gas bubbles show that a new substance is a gas at room temperature was probably produced Change in temperature- Temperature change shows that bonds are being broken and reformed to make a new substance Color Change- The color change shows that a new substance has a different pH than the original reactants. Cloudiness- A new substance (solid) is being formed. The new solid is precipitate. Rust- Metal reacts with oxygen to create a new substance.

What is the difference between a compound and a molecule?

Compound- A thing that is composed of two or more separate elements Molecule- A group of atoms bonded together, representing the smallest fundamental unit of a chemical compound that can take part in a chemical reaction. Everything on the Periodic Table is a molecule, but not everything can be a compound. Oxygen (O2) is not a compound because it is made up of two of the same element. Water (H2O) is an example of a compound because it is made up of two separate molecules.

Convection vs. Conduction

Convection- The movement caused within a fluid by the tendency of hotter and therefore less dense material to rise, and colder, denser material to sink under the influence of gravity, which consequently results in transfer of heat. (In a pot on the stove, hot water circulates to the top and cooler water sinks to the bottom). Conduction- The transfer of heat by the direct contact of particles of matter. Occurs between two materials at different temperatures when they are touching each other.

Which of the following best describes two atoms of oxygen that are chemically bonded to each other? a). Molecule b). Compound c). Solution d). Mixture

Correct Answer- A Molecule

Which set of coefficients will balance this chemical equation? __C2H4(g) + __O2(g) → 2CO2(g) + 2H2O(g) a). 1 and 2 b). 1 and 3 c). 2 and 3 d). 2 and 5

Correct Answer- B 1 and 3

What coefficient for O2 demonstrates the law of conservation of mass? CH4(g) + __O2(g) → CO2(g) + 2H2O(g) a). 1 b). 2 c). 3 d). 4

Correct Answer- B 2

What is formed when a sodium atom and chlorine atom react chemically? a). An Element b). A Compound c). An Electron d). An Neutron

Correct Answer- B A Compound

A chemical change happens when... a). Glass Breaks Into Pieces b). Dough Bakes In An Oven c). Ice Cream Melts Into A Liquid d). Electricity Flows Through A Wire

Correct Answer- B Dough Bakes In An Oven

Which statement best describes the change to an ice cube as it melts? a). The change is physical because the mass remains the same. b). The change is physical because the substance remains the same. c). The change is chemical because water has a different pH than ice. d). The change is chemical because ice has a lower density than water.

Correct Answer- B The change is physical because the substance remains the same.

Missy and Ethan discussed examples of the types of changes in matter. In which example is a chemical change taking place? a). A Piece Of Metal Is Cut In Half. b). An Ice Cube Melts On A Counter. c). A Camper Roasts Marshmallows Over A Burning Fire. d). A Baker Mixes Together Flour And Sugar To Make Dough.

Correct Answer- C A Camper Roasts Marshmallows Over A Burning Fire.

What happens to a wooden log when it is burned? a). It is completely destroyed. b). It is completely changed into heat energy. c). It changes into other types of matter and energy. d). It physically changes into the gaseous phase.

Correct Answer- C It changes into other types of matter and energy.

Correctly identify the type and number of each element in the following molecular formula Ca(NO3)2 a). 1 carbon atom, 1 neon atom, and 6 oxygen atoms b). 1 calcium atom, 2 neon atoms, and 3 oxygen atoms c). 1 carbon atom, 1 nitrogen atom, and 3 oxygen atoms d). 1 calcium atom, 2 nitrogen atoms, and 6 oxygen atoms

Correct Answer- D 1 calcium atom, 2 nitrogen atoms, and 6 oxygen atoms

A science class is doing an experiment performing the procedure shown. Experimental Procedure: 1. Grind salt into a powder. 2. Heat a small beaker of water. 3. Completely dissolve the salt in the water while stirring. 4. Add silver nitrate solution to form a white solid During which step of this procedure does a chemical change occur? a). Step 1 b). Step 2 c). Step 3 d). Step 4

Correct Answer- D Step 4

What type of equation is this? AB --> A + B

Decomposition

What type of equation is this? AB + C --> B + AC

Displacement

What type of equation is this? AB + CD --> BD + AC

Double Replacement (Also know as Precipitation Reaction) A new solid is formed from 2 liquids

Exothermic vs. Endothermic

Exothermic- If forming new bonds release more energy than it takes to break the old bonds, the reaction is exothermic (For example, creates/releases heat) Endothermic- If forming new bonds in the products releases less energy than it took to break the original bonds in the reactant. (Uses more energy than it releases)

Bond Types

Ionic Bond- Electrons are transferred to the other atom to fill energy levels (weak bond) Covalent Bonds- Valence electron are shared to complete energy level. (Strong bond/Hard to brake) Chemical Bond- is a lasting attraction between atoms, ions or molecules that enables the formation of chemical compounds. (Ionic compounds DO NOT form molecules, only covalent bonds form molecules). --> See notebook for drawing (page 105 for me)

Is Brittleness (Break ability) a physical or chemical property?

Physical