Chemical Reactions

chemical reaction

produce new substances by changing the way atoms are arranged

*break and make bonds

signs that a chemical reaction has occurred

color change, change in temperature, production of gas (bubbles), and production of a solid

color change example

rusty nail

temperature change

endothermic- heat added, exothermic- heat released

gas produces

bubbling ex. alkaseltzer

production of a solid (a precipitate)

a solid is produced, no heat was removed, so it is not a phase change

three main types of chemical reactions

synthesis (creating something), decomposition, and combustion

describe what happens to atoms involved in a chemical reaction

-bonds break in the reactants and new bonds form in the products

-the reactants and product has the same atoms

-then the atoms are rearranged

Tina made a volcano by pouring vinegar over a "mountain" of baking soda. The wet baking soda bubbled and foamed. Did a chemical reaction occur?

It is a chemical reaction since gas was produced.

Equilibrium

A state of balance

All chemical reactions involve _________________________________.

energy

Energy is used to _________________________ bonds in reactants.

break

Energy is ___________________________ when new bonds form in products.

released

exothermic reactions

release energy

endothermic reactions

absorb energy

law of conservation of energy

Energy cannot be created or destroyed

If energy cannot be destroyed during a chemical reaction, what happens to the energy that is absorbed in an endothermic reaction?

stored in the bonds of the products as chemical energy

What happens to the excess energy in the reactants of an exothermic energy?

When the reaction happens, the excess energy is released.

endothermic reaction

products have more stored chemical energy than the reactants

excess energy is released to the surrounding when the reactions occur

-example home heating system-energy is released during combustion in the furnace is used to heat the home

exothermic reactions

products have less stored chemical energy than the reactants

pure substances

single kind of matter and has specific set of properties

single kind of matter

elements and compounds

specific set of properties

chemical properties and physical properties

chemical properties

flammability, reactivity (oxidation), radioactivity, combustion, toxicity, new substance created, new properties

physical properties

texture, color, odor, density, luster, flexibility, solubility, physical state, conduction (heat/electric)

chemical reactions

matter, substance, compounds, physical and chemical properties

states of matter

solid, liquid, gas, phase change, melting, freezing, vaporization, condensation

heat/thermal

temperature, Celsius, heat, kinetic, molecular motion, thermal energy, mass

subscript

A number in a chemical formula that tells the number of atoms in a molecule

chemical equation

a way to describe a chemical reaction using chemical formulas and other symbols

reactants

substance that present at the beginning of a chemical reaction

products

substances formed (produced) by the chemical reaction

yield sign

the arrow in the middle of a chemical equation that separates reactants and products

coefficient

A number in front of a chemical formula in an equation that indicates how many molecules or atoms of each reactant and product are involved in a reaction.

chemical symbol

A one or two letter representation of an element

precipitate

A solid that forms from a solution during a chemical reaction.