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The scientific study of matter and its properties, the changes that matter undergoes, and the energy associated with those changes |
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is the “stuff ” of the universe: air, glass, planets, students—anything that has mass and volume. |
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What is the composition of matter? |
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the types and amounts of simpler substances that make it up |
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is a type of matter that has a defined, fixed composition. |
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| What three physical states does matter commonly occur in? |
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| has a fixed shape that does not conform to the container shape. Solids are not defined by rigidity or hardness: solid iron is rigid and hard, but solid lead is flexible, and solid wax is soft. |
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Has a varying shape that conforms to the container shape, but it fills the entire container and, thus, does not have a surface. |
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The characteristics that give each substance its unique identity. |
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What are the two types of changes that matter undergoes? |
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Physical Change (No Change in Composition)
Chemical Change (A Change in Composition)
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How do you identify a substance? |
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By observing two types of properties: Physical and Chemical |
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Define: Physical Properties |
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Characteristics a substance shows by itself, without changing into or interacting with another substance.
(These properties include color, melting point, electrical conductivity, and density.) |
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Occurs when a substance alters its physical properties, not its composition.
(For example, when ice melts, several physical properties change, such as hardness, density, and ability to flow.) |
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Define: Chemical change
(also known as Chemical Reaction) |
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Occurs when one or more substances are converted into one or more substances with different composition and properties.
(Water-----(electrical current)----->hydrogen + oxygen) |
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Define: Chemical properties |
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Characteristics a substance shows as it changes into or interacts with another substance (or substances).
(Chemical properties include flammability, corrosiveness, and reactivity with acids.) |
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The ability to do work.
(Physical and chemical changes are accompanied by energy changes) |
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The sum of its potential energy and its kinetic energy. |
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What is Potential Energy? |
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The energy due to the position of the object relative to other objects. |
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The energy due to the motion of the object. |
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What are the two central concepts of energy in the study of matter? |
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When energy is converted from one form to the other, it is conserved, not destroyed.
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Situations of lower energy are more stable and are favored over situations of higher energy, which are less stable.
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"The four cases"
1. A weight raised above the ground
2. Two balls attached by a spring
3. Two electrically charged particles
4. A fuel and its waste products
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The energy you exert to lift a weight against gravity increases the weight’s potential energy (energy due to its position). When you drop the weight, that additional potential energy is converted to kinetic energy (energy due to motion). The situation with the weight elevated and higher in potential energy is less stable, so the weight will fall when released, resulting in a situation that is lower in potential energy and more stable. |
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"The four cases"
1. A weight raised above the ground
2. Two balls attached by a spring
3. Two electrically charged particles
4. A fuel and its waste products
[image] |
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When you pull the balls apart, the energy you exert to stretch the relaxed spring increases the system’s potential energy. This change in potential energy is converted to kinetic energy when you release the balls. The system of balls and spring is less stable (has more potential energy) when the spring is stretched than when it is relaxed. |
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"The four cases"
1. A weight raised above the ground
2. Two balls attached by a spring
3. Two electrically charged particles
4. A fuel and its waste products
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Due to interactions known as electrostatic forces, opposite charges attract each other, and like charges repel each other. When energy is exerted to move a positive particle away from a negative one, the potential energy of the system increases, and that increase is converted to kinetic energy when the particles are pulled together by the electrostatic attraction. Similarly, when energy is used to move two positive (or two negative) particles together, their potential energy increases and changes to kinetic energy when they are pushed apart by the electrostatic repulsion. Charged particles move naturally to a more stable situation (lower energy). |
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"The four cases"
1. A weight raised above the ground
2. Two balls attached by a spring
3. Two electrically charged particles
4. A fuel and its waste products
[image] |
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Matter is composed of positively and negatively charged particles. The chemical potential energy of a substance results from the relative positions of its particles and the attractions and repulsions among them. Some substances are higher in potential energy than others. For example, gasoline and oxygen have more chemical potential energy than the exhaust gases they form. This difference is converted into kinetic energy, which moves the car, heats the interior, makes the lights shine, and so on. Similarly, the difference in potential energy between the food and air we take in and the wastes we excrete enables us to move, grow, keep warm, study chemistry, and so on. |
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What is the alchemical tradition? |
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| Alchemy was an occult study of nature that began in the 1st century AD and dominated thinking for over 1500 years. Originally influenced by the Greek idea that matter strives for “perfection,” alchemists later became obsessed with converting “baser” metals, such as lead, into “purer” ones, such as gold. They invented distillation, percolation, and extraction and devised apparatus still used routinely today (Figure 1.4). But perhaps even more important was that alchemists encouraged observation and experimentation, which replaced the Greek approach of explaining nature solely through reason. |
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What is the medical tradition? |
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| Alchemists also influenced medical practice in medieval Europe. And ever since the 13th century, distillates and extracts of roots, herbs, and other plant matter have been used as sources of medicines. The alchemist and physician Paracelsus (1493–1541) considered the body to be a chemical system and illness an imbalance that could be restored by treatment with drugs. Thus began the alliance between medicine and chemistry that thrives today. |
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What is the technological tradition? |
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| Pottery making, dyeing, and especially metallurgy contributed greatly to people’s experience with materials. During the Middle Ages and the Renaissance, books were published that described how to purify, assay, and coin silver and gold, how to use balances, furnaces, and crucibles, and how to make glass and gunpowder. Some of the books introduced quantitative measurement, which was lacking in alchemical writings. Nevertheless, the skilled artisans showed little interest in why a substance changes or how to predict its behavior. |
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The process of burning a material in air, often with the release of heat and light. |
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What is the phlogiston theory? |
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It proposed that combustible materials contain phlogiston, an undetectable substance released when the material burns. |
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Who is Antoine Lavoisier (1743–1794)? |
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He was a French chemist that resolved the conflict over phlogiston, through experimentation:
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Heating mercury calx decomposed it into two products—mercury and a gas—whose total mass equaled the starting mass of the calx.
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Heating mercury with the gas reformed the calx, and, again, the total mass remained constant.
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Heating mercury in a measured volume of air yielded mercury calx and left four-fifths of the air remaining.
A burning candle placed in the remaining air was extinguished.
Lavoisier named the gas oxygen and gave metal calxes the name metal oxides. His explanation of his results made the phlogiston theory irrelevant:
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Oxygen, a normal component of air, combines with a substance when it burns.
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In a closed container, a combustible substance stops burning when it has combined with all the available oxygen.
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A metal calx (metal oxide) weighs more than the metal because its mass includes the mass of the oxygen.
This new theory triumphed because it relied on quantitative, reproducible measurements, not on strange properties of undetectable substances. Because this approach is at the heart of science, many propose that the science of chemistry began with Lavoisier. |
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| What is the scientific method? |
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| To understand nature, scientists use this approach. A process of creative proposals and testing aimed at objective, verifiable discoveries of the causes of natural events. It includes observations, hypothesis, experiment, model (theory), and further experimentation. |
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| A fact obtained with the senses, often with the aid of instruments. Quantitative observations provide data that can be compared. |
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| Pieces of quantitative information obtained by observation. |
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| A summary, often in mathematical form, of a universal observation. When the same observation is made by many investigators in many situations with no clear exceptions |
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| A testable proposal made to explain an observation. If inconsistent with experimental results, a hypothesis is revised or discarded. |
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| A set of procedural steps that tests a hypothesis. |
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| A quantity that can have more than a single value |
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| Define controlled experiment |
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| An experiment that measures the effect of one variable at a time by keeping other variables constant. |
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| A simplified conceptual picture based on experiment that explains how a natural phenomenon occurs. |
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