Science Study Guide for the TEAS

Chemistry: The Basics

The TEAS 7 test requires you to not only demonstrate your understanding of anatomy and biology but also of chemistry. Throughout your nursing career, it will often be important to be able to understand and implement chemistry concepts.

Atomic Structure

Atoms are composed of three types of particles: positively charged protons, negatively charged electrons, and neutral neutrons. Protons and neutrons make up the nucleus, the central part of the atom. Electrons occupy the space around the nucleus in different energy levels, sometimes called shells, and most of the volume of the atom is taken up by the space between the nucleus and the electrons. An element’s nuclear symbol reveals how many protons, electrons, and neutrons make up an atom. It is important to be able to recognize atomic structure.

Atom

Atoms are the building blocks of all substances. Below are two diagrams. The first shows the parts of the atom and their relative locations. The second is a somewhat more accurate conceptualization of the relative size of the atom and its nucleus.

Retrieved from: https://www.ncbi.nlm.nih.gov/books/NBK26883/figure/A167/

Nucleus

The densest part of the atom is the nucleus, which contains both protons and neutrons. These particles are of equal size and mass but have different charges.

Protons

Protons are in the nucleus and have a positive charge. The number of protons an atom has determines what type of atom it is and what its chemical properties will be.

Neutrons

Neutrons are in the nucleus and have no charge. They, along with the protons, provide almost all the atomic mass of the atom.

Electrons

Electrons are tiny, very light particles with a negative charge. They occupy the region around the nucleus in what is called an electron cloud.

Shells

Electrons exist in different energy levels or shells. Each level can only contain a specific number of electrons. Additional electrons must exist at a higher energy level, further from the nucleus of the atom. An atom is most stable when its outermost electron shell is full.

Isotopes

Isotopes are atoms of the same kind that have a different number of neutrons, and therefore a different atomic mass. For example, most atoms of carbon have six protons and six neutrons, but some have eight neutrons instead. This isotope of carbon is known as carbon-14.

Quarks

The protons and neutrons in an atom are made up of even smaller particles known as quarks. There are six different types of quarks: up, down, top, bottom, charm, and strange, each with their own fractional charges.

Ions

Typically, an atom will have the same number of protons and electrons, and the positive and negative charges balance out. If an atom loses or gains electrons, it becomes an ion. An atom that has lost one or more electrons has a positive charge (cation), and one that has gained one or more electrons has a negative charge (anion).

The Periodic Table

The 118 known elements are displayed on the periodic table in a specific order. Progressing from left to right and top to bottom on the table, the elements increase in atomic number. A row in this table is called a period and a column is called a group. The elements in each period and group share certain properties.

Retrieved from: https://pixabay.com/illustrations/periodic-system-chemistry-science-1059755/

Covalent Bond

The attraction between atoms’ nuclei can create bonds to other atoms. Atoms bonded together can form groups called molecules. In a covalent bond, atoms will share electrons. The electrons will spend some time around each of the atoms in the molecule. Water is created with covalent bonds between one oxygen and two hydrogen atoms.

Ionic Bond

In an ionic bond, one of two atoms pulls electrons much more strongly than the other atom and the electrons move much closer to that first atom. The atom that attracted the electron more strongly becomes negatively charged, and the “weaker” atom becomes positively charged. The two oppositely charged atoms are then attracted to one another to create the ionic bond. Salt is created through an ionic bond between sodium (the cation) and chlorine (the anion).

Matter

Matter includes anything that has mass and takes up space. Matter is made up of atoms. A substance made of atoms of the same kind is an element, and one made of molecules of the same kind is a compound. Most matter consists of mixtures, which have many different elements and compounds mixed together. The properties of matter depend on the substances it’s made of. Physical properties can be observed without changing the chemical composition of a substance.

Physical Properties of Substances

The word substances has a specific meaning in chemistry. It can be made up of pure elements or pure compounds, but not mixtures of elements or mixtures of compounds. Substances must have a definite chemical composition and distinct chemical properties. A pure substance cannot be made into simpler components without some chemical change taking place.

Mass

Mass is a measurement of the amount of matter an object contains. An object’s weight is the measurement of gravity pulling on its mass. Weight can change if the force of gravity changes, but mass remains constant.

Volume

Volume describes how much space matter takes up. Volume is dependent on the type of atoms that make up a substance, how those atoms are arranged, and what state of matter the substance is in.

Density

Density measures how concentrated the mass of a substance is. Lead has a lot of mass concentrated in a certain volume, so we say it has a high density. Compared to lead, air has very little mass for the same volume, so we say it has a low density. To calculate density, divide mass by volume.

Freezing and Boiling Points

The freezing point of a substance is the temperature at which it turns from a liquid to a solid, or from a solid to a liquid. The boiling point is the temperature at which a substance turns from liquid to gas (bubbling begins), or gas to liquid (condensation). These points are dependent on pressure.

Color

A substance’s color depends on how light waves are reflected from its surface. Usually a change in color indicates that a chemical change has taken place.

States of Matter

Matter may exist in four main states (or phases): solid, liquid, gas, or plasma. The state depends on the temperature and the pressure of the system. Matter can change states if it experiences a change in energy. The states of matter vary in the way their atoms/molecules are configured and in the amount of energy the atoms have.

Solid

The atoms in a solid are tightly packed together and do not have enough energy to escape their attraction for each other. They are usually more dense than they are in liquid form (water is an exception to this; it becomes less dense when it freezes). Solids hold their shape and have a definite volume.

Liquid

The atoms in a liquid have enough energy to break loose from each other, but not enough to escape completely. Hence, they flow and move around each other. They are less dense than solids. They take the shape of their container and have a definite volume.

Gas

The atoms in gases have enough energy to completely escape from each other and will move far apart. Gases will expand to fill the space they are given. They have very low densities and have no definite shape or volume.

Plasma

Plasma is a rare state of matter (on Earth, anyway) and consists of extremely high-energy particles that have become ionized. The electrified gas in a neon lamp is plasma. The matter in the Sun and other stars is in the plasma state.

Effects of Pressure and Temperature

Changes of state are dependent on temperature, as we know from paying attention to the weather, but changes in pressure can affect a substance’s state as well. For example, gas can be compressed into a liquid state, even if it has not cooled to the condensation point.

Changes in States

The state that matter is in is dependent on temperature. For example, at room temperature, water is a liquid; but, below its freezing point of 0ºC (32ºF), it changes state and becomes a solid, ice. Likewise, above its boiling point of 100ºC (212ºF), it changes state and becomes a gas, steam. Other substances and mixtures also exist in these three states and have their own freezing/melting and boiling/condensing points. When a substance or mixture goes from one state to another, we call this a change of state. It is important to be able to compare and contrast the changes of state in matter.