Chemical Chemical EnergyEnergy

Fuel for LifeFuel for Life

What is What is Chemical Chemical Energy?Energy?• Chemical energyChemical energy is the is the energy that energy that

is storedis stored in the chemical composition in the chemical composition of matter.of matter.

• An example is the energy used by An example is the energy used by cells in your body come from the cells in your body come from the chemical energychemical energy in the food you in the food you eat.eat.– Energy is released as the chemical Energy is released as the chemical

compoundscompounds are broken apart. are broken apart.

Chemical Energy

Compounds

E E

E

What is a What is a Chemical Chemical Element?Element?

• A chemical elementchemical element is the simplest form of a substance (matter). – If a chemical elementchemical element is broken down it

becomes protons, neutrons and electrons (an atom).

• Chemical elementsChemical elements make up all the things in the physical world around us.

• Chemical elementsChemical elements are listed in the Periodic Table of the Elements

• Chemical elementsChemical elements combine to form moleculesmolecules and compounds.compounds.

What is an Atom? • Atoms are collections of tiny bits of

electricity, which we call protons, neutrons and electrons .

• When atoms come together to form larger clumps they are known as molecules.

• A molecule is a group of two or more atoms that stick together.

Example: O2, which is an oxygen

molecule made from two atoms of oxygen.

What is a What is a Chemical Chemical CompoundCompound??

•A chemical compoundchemical compound is the combination of one or more elements.

–Example: H2O, which is water made from two atoms of hydrogen and one atom of oxygen.

– Chemical compoundsChemical compounds can not easily be separated.

MixturesMixtures and and SolutionsSolutions• A mixturemixture is the combination of substances

that are not chemically combinednot chemically combined.– A mixturemixture can easily be separated (taken apart)

using physical means.– Example: Sand and iron mixture.

• A solutionsolution is the combination of substances in liquid form. A solutionsolution is like a liquid mixturemixture.– SolutionsSolutions are not chemically combined so they

can easily be separated.– Example: Salt dissolved in water.

• SolutionsSolutions can be acidic, or basic, or neutral.

This characteristic of solutions is called pH.

What is What is pHpH??• Every liquid you see will probably have either acidic or

basic traits.• Scientists use something called the pH scale to measure

how acidic or basic a liquid is.• pHpH stands for potential Hydrogen.• The pHpH of solutions are measured on a scale of 0 to 140 to 14. . 0 being the most acidic 14 being the most basic A value of 7 is considered neutral and is neither acidic or basic.

Examples:

stomach acid = pHpH of 2.5 distilled water= pH of 7

Soda ash = pHpH of 11

pH Scale

Distilled Water

What is a What is a Physical Physical ChangeChange??

• AA physical changephysical change is a change in a is a change in a substance where nothing new is substance where nothing new is created, (it does not change the created, (it does not change the chemical make up of the substance).chemical make up of the substance).– Example: Ice melts to water (both Example: Ice melts to water (both

are still Hare still H22O). O).

– Physical changes are usually Physical changes are usually changes in phase, or state of changes in phase, or state of matter.matter.

Solid

Liquid

The way the water looks (state of matter) is changing, but it is

still water!

The way something looks.

What is a What is a Chemical Chemical Change?Change?

• A chemical changechemical change is a …..change that does create something

new, (a new chemical make up results).– Example: When iron rusts. The iron (Fe)

becomes iron-oxide (Fe2O3).– Chemical changesChemical changes occur when elements

recombine with other elements, or in different combinations.

– Chemical changesChemical changes occur during chemical reactions.

ExothermicExothermic vs vs EndothermicEndothermic

• Chemical reactionsChemical reactions often involve heat and can be either exothermicexothermic or endothermicendothermic.

• ExothermicExothermic chemical reactionschemical reactions give off heat. give off heat. (feel hot)(feel hot)

• EndothermicEndothermic chemical chemical reactionsreactions take in heat. take in heat. (feel (feel cool)cool)

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