The nature of matter

transcript

Section 2.1

The Nature of Matter

•The Nature of Matter

Section 2.1

Objectives

1. To learn about the composition of matter

2. To learn the difference between elements and compounds

3. To define the three states of matter

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A. The Particulate Nature of Matter

• Matter has mass and occupies space. • It is composed of tiny particles called atoms.

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B. Elements and Compounds

Elements

• Elements contain only one type of atom – elemental copper contains only copper atoms and elemental gold contains only gold atoms.

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B. Elements and Compounds

Compounds

• Compounds are substances that contain two or more different types of atoms.

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C. The States of Matter

• Matter exists in three states:– Solid: a rigid substance with a definite shape – Liquid: has a definite volume but takes the shape of its

container – Gas: takes the shape and volume of its container

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Structure of a Solid

• Particles are held close togother in a regular arrangement or lattice.

• Not able to move freely,but simply vibrate in their fixed positions.

• Video Clip

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Structure of a Solid

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Structure of a Liquid

• Particles are closely packed together in an irregular arrangment.

• Able to move , flow and slide on each other.

• Video Clip

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Structure of a Liquid

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Structure of a Gas

• Particles are in continual straightline motion (randomly).

• The kinetic energy of the molecule is greater than the attractive force between them, thus they are much farther apart and move freely of each other.

• When the molecules collide with each other, or with the walls of a container, there is no loss of energy.

• Video Clip

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Structure of a Gas

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• The Kinetic Molecular Theory explains the forces between molecules and the energy that they possess. This theory has 3 main points :

– Matter is composed of small particles (atoms or molecules). • • • Particles are moving all the time.(higher Temp. higher of

average energy

– The molecules are in constant motion. This motion is different for the 3 states of matter.

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•Solid particles are close together in a regular pattern.

•They cannot move from one place to another place.

•Solid particles are vibrating about their positions all

the time.

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•Liquid particles are closer.

•They are moving continuously.

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A. Physical and Chemical Properties and Changes

• Properties are used to identify and separate the substance.

• Ex: Substance = metals Properties = conduct electricity

• Matter has both physical and chemical properties. – Chemical properties describe a substance’s ability to change

to a different substance.

– Physical properties are the characteristics of a substance that do not involve changing to another substance.

• Examples are: shape, size and color, melting point, boiling point

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A. Physical and Chemical Properties and Changes

• Matter undergoes physical and chemical changes.

– A physical change involves a change in one or more physical properties but no change in composition.

– Ex:melting, boiling, freezing

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B. Physical and Chemical Properties and Changes

• Matter undergoes physical and chemical changes.

– A chemical change transforms a substance into one or more new substances.

– Ex: electrolysis

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1. To learn to distinguish between mixtures and pure substances

2. To learn methods of separating mixtures

Objectives

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A. Mixtures and Pure Substances

• Matter can be classified as a mixture or a pure substance.

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Classification of Matter:

• Mixtures = a blend of two or more kinds of matter, each of which retains its own identity and properties.

• - Parts can mixed together physically and usually can be separated.

• - Contain various amounts of different substances, so the composition needs to be specified. (% Mass = EX: 5 % NaCl and 95 % water)

• Homogeneous (solutions): Uniform in composition (Saltwater, air, milk, alloys)

• Heterogeneous: not uniform throughout (can be separated) (pizza, concrete, salad)

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A. Mixtures and Pure Substances

• A pure substance always has the same composition. • Pure substances are of two types:

– Elements which cannot be broken down chemically into simpler substances

– Compounds which can be chemically broken down into elements

Water is a compound. All thecomponents are the same—H2O molecules.

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Homogeneous Mixtures

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Mixture vs. Solution

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Mixture vs. Compound

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Summary: The Organization of Matter

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Separation techniques of mixtures:

• Filtration = to filter a solid from a liquid– Filtrate– Residue– Decant = used when the mixture consists of

substances of different densities. • The less dense substances is carefully poured

off of the more dense one.

• Centrifugation - used when the substances have very similar densities, or when one of the substances consists of very fine particles suspended in a liquid.

• Electrolysis – electric current to separate water into hydrogen gas and oxygen gas

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B. Separation of Mixtures

Mixtures can be separated into pure substances by various means.

• filtration

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ChromatographyThis technique separates substances (dyes and pigments) on the basis of differences in solubility in a solvent.

Paper Chromatography = A solvent travels through paper by capillary action

and carries the pigments with it. Different pigments are deposited at different

places on the paper depending on how much they like the solvent compared to

how much they like to stick to the paper.

Solvent

Solute

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Separation Techniques

• Distillation = to remove dissolved substances from a liquid or to separate a mixture of liquids that have different boiling points.

• The original liquid is heated. • The temperature is measured. • The vapor is collected and condensed back into a liquid. • The new liquid is collected.

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B. Separation of Mixtures

Mixtures can be separated into pure substances by various means.

• distillation

The nature of matter

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