Chemistry Ch. 1

___ have a definite volume, but no definite shape. Liquids adopt the shape of their container.

Liquids

When a substance changes into something different, it has undergone a ___.

chemical change.

Changes the produce new substances; also called chemical reactions.

chemical changes

Properties of a substance that cannot be measured without changing the identity of a substance.

chemical properties

___ are properties that we cannot measure without changing the identity of a substance. For example, flammability is a ___ property.

chemical properties

Changes that produce new substances; also called chemical changes.

chemical reactions

Chemical changes are also called ___. In some ___, elements combine to form compounds. For example, when heated, zinc, and sulfur combine to form new compounds. For example, methane gas can react with oxygen gas to produce two new compounds, carbon dioxide and water. The key idea is that ___.

chemical reactions; a chemical change always involves the formation of a different substance.

Understanding what substances are made of and how they behave are the essence of the field of ___.

chemistry

___ is sometimes referred to as the "the central science," because it connects with every other field in the sciences.

chemistry

___ is the study of matter and its changes.

chemistry

The components that make up a material.

composition

___ refers to the simple components that make up the material.

composition

___ are substances composed of more than one element, bound together in fixed ratios. For example, water is made of two parts hydrogen and one part oxygen. If the ration of hydrogen to oxygen changes at all from 2:1, it is no longer water, but some other substance.

compounds

___ cannot be separated without changing the substances into their elemental forms.

compounds

different types of atoms bound together

compounds

A transition from the gas phase to the liquid phase.

condensation

If we cool it, the reverse occurs: The gas changes to a liquid ( ___ ).

condensation

A substance made of only one type of atom.

element

The simplest form of matter is an ___.

element

one type of atom

elements

A change that absorbs energy.

endothermic change

The ability to do work.

energy

A change the releases heat energy.

exothermic change

To test a hypothesis, scientists devise ___. The results of ___ provide support for or against a hypothesis, and they lead scientists to embrace, refine, or discard their ideas. The observations that scientists make from ___ often lead to new hypothesis, which in turn lead to new ___.

experiments

A transition from the liquid phase to the solid phase.

freezing

The liquid changes to a solid ( ___ ).

freezing

A state of matter that does not have a definite shape or a definite volume. The particles in a gas move freely with very little interactions.

gas

___ do not have a definite shape or a definite volume. ___ fill any container they occupy.

gases

Common elements include gold, silver, iron, oxygen, and nitrogen. For example, gold contains only ___ atoms, and silver contains only ___ atoms.

gold; silver

A type of kinetic energy involving the movement of particles within a change.

heat energy

___ energy is a type of kinetic energy. ___ energy involves the kinetic energy of the particles within a substance.

heat energy

Sand and water, gravel, and chocolate-chip cookie dough are all ___ mixtures.

heterogeneous

___ mixtures contain regions with significantly different composition.

heterogeneous

Mixtures in which the components are not evenly blended throughout.

heterogeneous mixtures

When something has ___ (either kinetic or potential), it can bring about a change.

high energy

In chemistry, we often describe substances as either ___ or ___.

high energy or stable

Metal alloys, a cup of coffee, and the air around us are all ___ mixtures.

homogeneous

components are evenly blended

homogeneous

Mixtures in which components are evenly blended throughout.

homogeneous mixtures

Mixtures whose components are evenly blended throughout are called ___.

homogeneous mixtures

A tentative explanation that has not been tested.

hypothesis

Scientists use the term ___ to describe a tentative explanation that has not been tested.

hypothesis

At higher temperatures, particles have more ___ energy.

kinetic

___ energy is the energy of motion.

kinetic

The energy of motion.

kinetic energy

Describe each property as physical or chemical: - A paint has a deep blue color.

physical

Describe each property as physical or chemical: - An iron bar heats up quickly if left out in the sun.

physical

Changes that do not alter the identity of the substance.

physical changes

___ are changes that occur without altering the identity of the substance. For example, we can take an iron bar, melt it, pour it into a mold, and let it cool, solidifying into a new shape.

physical changes

Chemists study the properties of matter and also the ways that matter can change. We commonly describe both properties and changes as being ___ or ___.

physical or chemical

The properties of a substance that can be measured without changing the identity of the substance.

physical properties

___ are the properties of a substance that we can measure without changing the identity of the substance. For example, we can measure color, temperature, mass, volume, shape, hardness, flexibility, and a host of other factors without changing the composition of that substance.

physical properties

Substances with a large amount of ___ energy are more likely to react.

potential

The ___ energy in any substance depends on its structure.

potential

___ energy refers to energy that is stored.

potential

Energy that is stored.

potential energy

Both the element copper and the compound water are examples of ___: materials that are composed of only one element or compound.

pure substances

Substances composed of only one element or only one compound.

pure substances

one element or compound

pure substances

Matter is composed of either ___ and ___.

pure substances and mixtures

A statement that describes observation that true in widely varying circumstances. Scientific laws often describe mathematical relationships. However, they do not explain why something occurs; they only observe that it occurs.

scientific law

Scientists use the term ___ to describe observations that are true in widely varying circumstances. A ___ does not explain why something occurs; it simply observes that is true. Often, a ___ describes a mathematical relationship. For example, consider the law of gravity: This law describes observations and phenomenon that consistently occur. Scientists use the law of gravity mathematically, to calculate the weight of a building or the trajectory of a rocket. This law predicts what will happen, but it does not explain why it happens.

scientific law

A cyclical process of making observations, formulating new ideas, and then testing those ideas through experiments.

scientific method

The approach that scientists take to solving problems is called the ___.

scientific method; at its core, the scientific method is a cyclical process of making observations, formulating new ideas, and then testing those ideas through experiments.

A state of matter having definite shape and definite volume. The particles in a liquid are close together but move freely past each other.

solid

___ have both a definite shape and a definite volume.

solids

If something is ___, it has less energy and is therefore less likely to react.

stable

The classification of matter as a solid, liquid, or gas ( also called the phases of matter ).

states of matter

Matter typically exists in one of three forms, which we call the three ___, or sometimes the three ___.

states of matter; phases of matter.

Energy is ___, when a tree grows by absorbing energy from the sun to convert carbon dioxide and water into plant material.

stored

The arrangement of simple units within a substance. In chemistry, structure refers to both the composition and arrangement of simple units within a substance.

structure

___ refers to both the composition and arrangement of those simpler substances.

structure

When charcoal burns, the charcoal (which is composed of carbon) reacts with oxygen to produce carbon dioxide and heat, as represented in the equation shown here. Which has the higher potential energy: carbon plus oxygen, or carbon dioxide? Which is more stable? Is this reaction endothermic or exothermic?

Carbon + oxygen -> carbon dioxide + heat This chemical change involves the release of energy. This means the substance formed by the change (carbon dioxide) has less potential energy than the substances that were present before the change (carbon and oxygen). Since carbon dioxide has less potential energy, it is more stable. And because this change released energy, we refer to it as a exothermic change.

Describe each property as physical or chemical: - Zinc metal reacts with hydrogen chloride gas to form zinc chloride and elemental hydrogen.

Chemical

Pure substances composed of more than one element in a fixed ratio.

Compounds

___ is the ability to do work.

Energy

Groups of atoms that are held tightly together.

Molecules

___ : The behavior of any substance is determined by the arrangement of the particles that compose the substance.

The states of matter offer an importance lesson

An element is a substance that is made of only one type of ___.

atom

Scientist represent ___ as tiny spheres, or by using one- or two-letter symbols, or by using both together.

atoms

The fundamental units of matter.

atoms

___ are the fundamental units of matter.

atoms

A state of matter that does not have a definite volume but no definite shape. The particles in a liquid are close together but move freely past each other.

liquid

Anything that has mass and takes up volume

matter

The world around us is composed of ___. ___ is anything that has mass and takes up volume.

matter

A transition from the solid phase to the liquid phase.

melting

If we heat a substance, it can transition from solid to liquid ( ___ ).

melting

Substances containing more than one substance.

mixtures

more than one substances

mixtures

In contrast to pure substances, ___ contain more than one substance - and the substances are not bound in a fixed ratio. For example, brass and bronze are both mixtures of metals, known as ___.

mixtures; alloys

Key difference between compounds and mixtures is that ___ can be separated into their individual components without changing the identity of the substances. For example, chemists commonly use a technique called ___ to separate heterogeneous mixtures.

mixtures; filtration

Many compounds form groups of atoms called ___. In ___, the atoms bind tightly together and behave as a single unit. For example, a water molecule contains two hydrogen atoms and one oxygen atoms. Some elements also exist as molecules. In hydrogen, nitrogen, and oxygen, the atoms of the element pair together to form ___ ("two-atom") molecules.

molecules; diatomic

An idea that has been tested and refined; also a way of thinking about a particular topic.

theory

Through the cyclic process, scientists refine their ideas over time. A ___ is an idea that is supported by experimental evidence. This term can also have a broader meaning: Sometimes it is used to mean a ___ - a way of thinking about a particular topic.

theory; paradigm

A transition from the liquid phase to the gas phase.

vaporization

Liquid to gas ( ___ ).

vaporization