chemical reactions

chemical reaction

The process in which atoms are rearranged to create new substances

During a chemical reaction, _________.

the bonds that hold atoms together may be formed or broken

signs of chemical reactions

formation of a precipitate, change in color, odor, the appearance of gas bubbles.

Chemical formula

Uses chemical symbols and numbers to represent a given substance

Subscripts

The numbers written below and to the right of chemical symbols that tell you how many of each type of atom are in a molecule

Chemical equation

An expression that uses symbols to show the relationship between the starting substances and the substances that are produced by a chemical reaction

Reactants

The substances that participate in a chemical reaction

Products

The substances formed in a chemical reaction

yields sign

an arrow that points from reactants to products

Law of conservation of mass

Matter is neither created nor destroyed in ordinary chemical and physical changes

balancing an equation

when the reactants and products contain the same number of atoms of each element

coefficients

A number that is placed in front of a chemical formula

endothermic reactions

chemical reactions that require an input of energy is called an endothermic reaction

example of endothermic process

photosynthesis

Exothermic reaction

A chemical reaction in which energy is released to the surroundings

Law of conservation of energy

States that energy cannot be created or destroyed, but can change form

what affects the rates of reactions?

concentration, surface area, temperature, catalysts

how does concentration affect the rate of reaction?

at higher concentration, there are more reactants in a given volume. the reaction rate is higher when reactant concentration is higher.

how does surface area affect the rate of reaction?

reaction rate increases when more reactant particles are exposed to one another

how does temperature affect the rate of reaction?

particles move faster at higher temperatures. because the reactant particles move more quickly, they are more likely to collide and react

Catalyst

A substance that changes the rate of a chemical reaction without being used up or changed very much