“STUFF”

Matter and Energy

What is Matter?

Matter is anything that has both mass and volume.

Mass is a measurement of the amount of “stuff” in an object.

Volume is a measurement of the quantity of space that an object occupies.

Note: Weight is not the same thing as mass. Weight is the force of gravity on an object.

What is Matter Made of?

All matter is made up of atoms.An atom is the smallest unit of an element that has the properties of that element.

All of the known elements can be found on the Periodic Table.

Atoms are combined in various ways to make up all of the different kinds of matter.

Physical Properties

A physical property of a substance is a characteristic that can be observed or measured without changing the chemical makeup of a substance.

Physical properties include:color odor

density viscosity

hardness malleability

melting point electrical conductivity

boiling point slipperiness

Extensive vs. IntensiveProperties

Depend on amount of substance present mass length volume

Independent of amount of substance density boiling point melting point

Chemical Properties

A chemical property is a characteristic of matter that describes the ability of a substance to change (or not change) composition when in contact with other substances.

Examples of chemical properties include:burns in air is toxicexplodes decomposes when heatedreacts with certain acidsreacts with certain metals

Physical Changes

A physical change is a change in a substance that does not involve a change in the identity of the substance.

grinding, cutting, melting, and boiling

A change of state is a physical change of a substance from one state to another.

States of Matter

Solid – definite shape and volumeLiquid – constant volume but shapes

changes with the containerGas – takes shape of container and

fills the entire volume of the containerPlasma – ionized, highly reactive gas

Chemical Changes

A change in which one or more substances are converted into different substances is called a chemical change or chemical reaction.

The key difference between a physical and chemical change is that a chemical change always produces a new substance. In a physical change, the substance does not change into something else.

Describing a Chemical Reaction

Indications of a Chemical Reaction

Evolution of heat, light, and/or sound

Production of a gas

Formation of a precipitate

Color change

Signs of Chemical Reactions

There are five main signs that indicate a chemical reaction has taken place:

change in color change in odor production of newgases or vapor

input or releaseof energy

rele

ase

inpu

t

formation of precipitate

Chemical Reactions

The starting substances turn into different substances by rearranging the atoms.

Mass is conserved in chemical reactions.

Starting substances = reactantsEnding substances = products

Energy

• Energy is always involved when physical or chemical changes occur.

• Energy can be in various forms.• heat • light

• Energy can be absorbed or released in a change, it is not destroyed or created.(This is called the law of conservation of energy.)

Temperature

Temperature is a measure of the average kinetic energy of the particles in a sample of matter.(This is related to how fast the particles are moving. If two particles are identical, the one moving faster has more kinetic energy.)

The greater the kinetic energy of the particles in a sample, the hotter it feels. Example: the particles in liquid water move faster than the

particles in ice.For calculations in chemistry, the Celsius

and Kelvin temperature scales are used.

Heat

Heat can be thought of as the energy transferred between samples of matter because of a difference in their temperatures.

• Energy transferred as heat always moves a higher temperature to a lower temperature.

Image from OpenStax College Physics

Energy in Chemical Reactions

A chemical reaction that releases energy is exothermic, and the energy of the products is less than the energy of the reactants. The products in an exothermic reaction will feel

warmer than the reactants.In an endothermic reaction, the products

have a higher energy than the reactants, and the reaction absorbs energy. The products in an endothermic reaction will

feel colder than the reactants.

Pure Substances

A pure substance contains only one kind of particle. A pure substance has a set of definite physical and chemical properties.

Types of pure substances:An element has only one kind of atom.A compound is made by combining

atoms of 2 or more different elements. Compounds can be broken down into elements.

Pure Substances

Element composed of identical atoms EX: copper wire, aluminum foil

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Pure Substances

Compound composed of 2 or more elements

in a fixed ratio

properties differ from those of individual elements

EX: table salt (NaCl)

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Mixtures

A mixture is the combination of two or more substances that remain chemically separate.

A homogeneous mixture is a combination that is uniform in composition and appearance.

A heterogeneous mixture is uneven in composition and appearance. A heterogeneous mixture can usually be visibly identified as a mixture.

Mixtures

Variable combination of 2 or more pure substances.

Heterogeneous Homogeneous

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Mixtures

Heterogeneous Homogeneous

•does not blend smoothly•multiple substances can be seen

•has a uniform composition•also called a solution

Mixtures

Solutiono homogeneouso very small particleso no Tyndall effecto particles don’t settleo EX: rubbing alcohol

o Tyndall effect = light is scattered as it passes through (appears cloudy)

Tyndall Effect

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Mixtures

Colloidheterogeneousmedium-sized particlesTyndall effectparticles don’t settleEX: milk

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Mixtures

Suspension heterogeneous large particles Tyndall effect particles settle EX: fresh-squeezed

lemonade

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Mixtures

Examples: mayonnaise

muddy water

fog

saltwater Italian salad

dressing

colloid

suspension

colloid

solution

suspension

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MATTER

Can it be physically separated?

Homogeneous Mixture

(solution)

Heterogeneous Mixture Compound Element

MIXTURE PURE SUBSTANCE

yes no

Can it be chemically decomposed?

noyesIs the composition uniform?

noyes

Colloids Suspensions

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