TEAS chemistry: the topics, rules and practice to know
Chemistry is 8 of the 44 scored questions on TEAS science. ATI's outline names six topics: atomic structure, physical properties and changes of matter, chemical reactions, how conditions change a reaction, properties of solutions, and acids and bases. Each is below with the rules the questions use, worked examples, 10 practice questions and a 10-day plan.
It is high-school chemistry, mostly concepts with a little arithmetic: reading the periodic table, balancing an equation, telling a physical change from a chemical one, comparing pH values. The calculator built into the exam handles the arithmetic.
How many chemistry questions are on the TEAS?
| Science content area | Scored questions |
|---|---|
| Human anatomy and physiology | 18 |
| Biology | 9 |
| Scientific reasoning | 9 |
| Chemistry | 8 |
| Total | 44 scored + 6 unscored = 50, in 60 minutes |
Counts are ATI's for the TEAS Version 7, the current exam (what is on the TEAS test has the whole exam). Eight questions is the smallest science block, about 18% of the scored section. Chemistry also shows up inside other questions: pH in blood and the stomach, diffusion in the lungs, and solutions in the cell questions. So the hours here pay twice. For the order to study all four science areas, read how to study for the TEAS science section.
The six chemistry topics on the TEAS
| ATI topic | What the questions ask |
|---|---|
| Atomic structure | Protons, neutrons, electrons; atomic number and mass; isotopes and ions; periodic table trends |
| Physical properties and changes of matter | States of matter, phase changes, physical vs chemical change, density |
| Chemical reactions | Reaction types, balancing equations, bonds, conservation of mass |
| How conditions affect reactions | Temperature, concentration, surface area, catalysts and enzymes |
| Properties of solutions | Solute and solvent, concentration, saturation, molarity, dilution, osmosis |
| Acids and bases | The pH scale, acid and base traits, neutralization, buffers |
Topic names are from ATI's Version 7 content outline. ATI doesn't say how many questions each topic gets; with 8 questions and 6 topics, plan on one or two each.
Atomic structure and the periodic table
| Particle | Charge | Where | Mass |
|---|---|---|---|
| Proton | +1 | Nucleus | About 1 atomic mass unit |
| Neutron | 0 | Nucleus | About 1 atomic mass unit |
| Electron | −1 | Around the nucleus, in shells (energy levels) | Almost none (about 1/1,836 of a proton) |
- Atomic number = number of protons. It decides which element an atom is: every carbon atom has 6.
- Mass number = protons + neutrons. So neutrons = mass number − atomic number. Carbon-14 has 14 − 6 = 8 neutrons.
- Isotopes are atoms of one element with different numbers of neutrons (carbon-12 and carbon-14).
- Ions are atoms that gained or lost electrons. Lose electrons: positive ion (Na+). Gain electrons: negative ion (Cl−). The protons never change in a chemical reaction.
- A neutral atom has as many electrons as protons.
- Valence electrons are those in the outer shell; they decide how an atom bonds. Atoms tend to gain, lose or share electrons until the outer shell is full (eight for most: the octet rule).
Reading the periodic table. Rows are periods; columns are groups. Elements in one group have the same number of valence electrons and act alike: group 1 (alkali metals such as sodium and potassium) react strongly and lose one electron; group 17 (halogens such as chlorine) gain one; group 18 (noble gases) have full shells and barely react. Metals sit on the left, nonmetals on the right.
| Trend | Across a period (left to right) | Down a group |
|---|---|---|
| Atomic radius (size) | Gets smaller | Gets bigger |
| Electronegativity (pull on shared electrons) | Rises | Falls |
| Ionization energy (energy to remove an electron) | Rises | Falls |
One picture covers all three: fluorine, top right (noble gases aside), holds its electrons hardest and is small; cesium and francium, bottom left, are big and give electrons up easily.
Chemical bonds
| Bond | How | Between | Example |
|---|---|---|---|
| Ionic | Electrons transferred; opposite ions attract | A metal and a nonmetal | NaCl, table salt |
| Covalent, nonpolar | Electrons shared equally | Two nonmetals that pull alike | O2, CH4 |
| Covalent, polar | Electrons shared unequally | Nonmetals that pull differently | H2O (oxygen pulls harder) |
| Hydrogen bond | Weak attraction between molecules, not inside one | H on O, N or F, and a nearby O, N or F | Between water molecules; holds DNA's two strands together |
Hydrogen bonds explain water's high boiling point and surface tension, and why ice floats: in ice they hold molecules in an open pattern, so ice is less dense than liquid water.
Physical properties and changes of matter
Solids have a fixed shape and volume; liquids a fixed volume but take the shape of their container; gases fill whatever holds them. Heat makes particles move faster, which is what moves matter from solid to liquid to gas.
| Change | From → to | Energy |
|---|---|---|
| Melting | Solid → liquid | Absorbed |
| Freezing | Liquid → solid | Released |
| Vaporization (boiling, evaporation) | Liquid → gas | Absorbed |
| Condensation | Gas → liquid | Released |
| Sublimation | Solid → gas (dry ice) | Absorbed |
| Deposition | Gas → solid (frost) | Released |
Physical vs chemical change. A physical change alters form but not what the substance is: melting ice, dissolving sugar, cutting paper. A chemical change makes a new substance: burning, rusting, digesting food, baking. Signs of a chemical change: a new gas (bubbles), a color change, light or heat given off, a solid (precipitate) forming from two liquids. Boiling water bubbles too, but it is still water, so it is physical; that is the classic trap.
Density = mass ÷ volume. A 20 g object with a volume of 4 mL has a density of 5 g/mL. Anything less dense than water (1 g/mL) floats in it.
Chemical reactions and balancing equations
| Type | Pattern | Example |
|---|---|---|
| Synthesis | A + B → AB | 2H2 + O2 → 2H2O |
| Decomposition | AB → A + B | 2H2O2 → 2H2O + O2 |
| Single replacement | A + BC → AC + B | Zn + 2HCl → ZnCl2 + H2 |
| Double replacement | AB + CD → AD + CB | AgNO3 + NaCl → AgCl + NaNO3 |
| Combustion | Fuel + O2 → CO2 + H2O | CH4 + 2O2 → CO2 + 2H2O |
Reactants are on the left, products on the right. Mass is conserved: every atom on the left must be on the right, which is why equations are balanced.
Balancing, step by step, with methane burning: CH4 + O2 → CO2 + H2O.
- Count each element on both sides. Left: C 1, H 4, O 2. Right: C 1, H 2, O 3.
- Balance the element that appears in the fewest compounds first, leaving O and H for last. Carbon is already 1 and 1.
- Hydrogen: 4 on the left, so put a 2 in front of H2O. Right now has H 4, O 4.
- Oxygen: 4 on the right, so put a 2 in front of O2.
- Check: CH4 + 2O2 → CO2 + 2H2O. C 1 = 1, H 4 = 4, O 4 = 4.
Change only the big numbers in front (coefficients), never the small ones (subscripts): changing H2O to H2O2 makes a different substance. On a multiple-choice question it is often faster to test each answer's coefficients than to balance from scratch.
Energy. An exothermic reaction gives off heat (burning, a hand warmer); an endothermic one takes it in (an instant cold pack).
How conditions affect chemical reactions
A reaction happens when particles collide hard enough and the right way. Anything that makes useful collisions more frequent speeds it up.
| Change | Effect on rate | Why |
|---|---|---|
| Higher temperature | Faster | Particles move faster and hit harder |
| Higher concentration (or gas pressure) | Faster | More particles in the same space, more collisions |
| More surface area (powder vs lump) | Faster | More particles exposed |
| Catalyst | Faster | Lowers the activation energy; is not used up |
| Lower temperature | Slower | The reason food is refrigerated |
Enzymes are the body's catalysts, almost all of them proteins. Each works best at one temperature and pH (near 37 °C for most human enzymes; pepsin in the acid stomach, trypsin in the near-neutral small intestine). Too much heat or the wrong pH changes the enzyme's shape (denatures it) and it stops working. A catalyst speeds a reaction; it doesn't change how much product you end up with.
Properties of solutions
| Word | Means |
|---|---|
| Solute | What gets dissolved (salt) |
| Solvent | What does the dissolving (water, "the universal solvent") |
| Concentrated / dilute | Much / little solute per amount of solution |
| Unsaturated | Can dissolve more solute |
| Saturated | Holds all the solute it can at that temperature |
| Supersaturated | Holds more than it normally could; unstable, crystals form easily |
Solubility. "Like dissolves like": polar solvents (water) dissolve polar and ionic solutes (salt, sugar); nonpolar ones dissolve nonpolar solutes (oil in oil, not in water). Most solids dissolve better in hotter water; gases dissolve better in colder water, which is why warm soda goes flat faster.
Molarity (M) = moles of solute ÷ liters of solution. Worked: NaCl's molar mass is 23.0 + 35.5 = 58.5 g per mole, so 117 g is 2 moles; dissolved to make 1 L of solution, that is 2 M. In 0.5 L it would be 4 M.
Dilution: M1V1 = M2V2. To make 100 mL of 1 M solution from a 4 M stock: 4 × V1 = 1 × 100, so V1 = 25 mL of stock, topped up to 100 mL with water.
Osmosis is water moving across a membrane from the side with less solute to the side with more. A cell in a hypotonic solution (less solute outside) swells and may burst; in a hypertonic solution (more solute outside) it shrinks; in an isotonic solution it stays the same. Normal saline used in IV drips, 0.9% sodium chloride, is isotonic with blood. This question often sits on the biology side of the section too.
Acids, bases and the pH scale
| Acid | Base | |
|---|---|---|
| pH | Below 7 | Above 7 |
| Does what with H+ | Releases (donates) it | Accepts it, or releases OH− |
| Traits | Sour; turns blue litmus red | Bitter, slippery; turns red litmus blue |
| Examples | Stomach acid (HCl), lemon juice, vinegar | Sodium hydroxide (NaOH), baking soda, ammonia, bleach |
- The scale runs 0 to 14; pure water is 7, neutral.
- Each step is ten times: pH 3 is 10 times more acidic than pH 4 and 100 times more than pH 5. A question that compares two pH values two steps apart wants 100, not 2.
- Lower pH = more H+ = more acidic.
- Neutralization: acid + base → salt + water. HCl + NaOH → NaCl + H2O.
- Buffers resist a change in pH. Blood is kept between about 7.35 and 7.45 mostly by the bicarbonate buffer, with help from the lungs (breathing out CO2) and the kidneys. Below that range is acidosis, above it alkalosis.
10 TEAS chemistry practice questions
Cover the answers and give yourself 72 seconds each, the section's pace.
- An atom has 17 protons, 18 neutrons and 18 electrons. What is its charge?
Answer: −1. One more electron than protons; this is a chloride ion. - Which element has the larger atomic radius, sodium or chlorine (same period)?
Answer: sodium. Radius shrinks left to right across a period. - Balance: __Al + __O2 → __Al2O3.
Answer: 4, 3, 2. Al 4 = 4; O 6 = 6. - Which is a chemical change: (a) ice melting (b) salt dissolving (c) iron rusting (d) water boiling?
Answer: (c). Rust is a new substance. - Which reaction type is AgNO3 + KCl → AgCl + KNO3?
Answer: double replacement. - A solution has pH 2 and another pH 4. How many times more acidic is the first?
Answer: 100. Two steps on a tenfold scale. - Which change would slow a reaction: (a) crushing a solid reactant (b) adding a catalyst (c) cooling the mixture (d) raising concentration?
Answer: (c). - How many moles of glucose are in 2 L of a 0.5 M glucose solution?
Answer: 1 mole. 0.5 × 2. - Red blood cells are placed in pure water. What happens, and why?
Answer: they swell and may burst. Pure water is hypotonic; water moves into the cells. - What bond holds Na+ and Cl− together in table salt?
Answer: an ionic bond.
To see how chemistry sits next to your other sections, take our free TEAS practice test: 15 questions across all four sections, scored against your program's minimum. The TEAS science practice test then gives you 20 more science questions with answers.
A 10-day plan for TEAS chemistry
About 30 minutes a day: 20 minutes on one block of this page, 10 minutes of questions. Chemistry is the smallest science block, so if your date is close, give anatomy and physiology (18 questions) the bigger share first.
| Day | Study | Done when you can |
|---|---|---|
| 1 | Particles, atomic number, mass number | Find protons, neutrons, electrons for any atom or ion |
| 2 | Periodic table groups and trends | Say which of two elements is bigger or more electronegative |
| 3 | Bonds | Name the bond in NaCl, O2, H2O, and between water molecules |
| 4 | States, phase changes, physical vs chemical | Sort 10 everyday changes in under 2 minutes |
| 5 | Reaction types and balancing | Balance 5 equations, under a minute each |
| 6 | Reaction rates and enzymes | Explain each rate factor in one sentence |
| 7 | Solutions, molarity, dilution | Do a molarity and a dilution problem without notes |
| 8 | Osmosis and tonicity | Say what a cell does in each of the three solutions |
| 9 | Acids, bases, pH, buffers | Compare two pH values; write a neutralization |
| 10 | All 10 questions above, timed, then a mixed science set | Every miss traced to its section and redone |
Mistakes that cost points on TEAS chemistry
- Treating pH as a straight line. One step is ten times, two steps a hundred.
- Changing subscripts to balance. Only coefficients change; subscripts define the substance.
- Calling boiling or dissolving chemical. Bubbles and disappearing solids aren't proof of a new substance.
- Mixing up mass number and atomic number. Atomic number is protons only, and it never changes for an element.
- Getting the periodic trends backwards. Size grows down and to the left; electronegativity grows up and to the right.
- Thinking a catalyst makes more product. It only makes the same product faster.
- Mixing up hypotonic and hypertonic. The words describe the solution outside the cell: hypo has less solute, so water rushes in.
Anatomy and physiology is more than twice as many points as chemistry; our TEAS anatomy and physiology guide covers its 12 topics the same way.
TEAS chemistry FAQ
Is chemistry on the TEAS test?
Yes. Chemistry is one of the four science content areas on the TEAS 7: 8 of the 44 scored science questions.
How much chemistry is on the TEAS?
8 scored questions, about 18% of scored science. Chemistry ideas also appear in anatomy and physiology and biology questions (blood pH, diffusion, osmosis).
Do I need to memorize the periodic table for the TEAS?
No. ATI publishes no list of elements to memorize. What the questions use is how to read the table: groups, periods, valence electrons and the size and electronegativity trends. Knowing the symbols of common elements (H, C, N, O, Na, K, Cl, Ca, Fe) saves time.
Is there math in TEAS chemistry?
A little: neutrons from mass and atomic number, density, molarity, dilution and counting atoms to balance. The exam has a built-in calculator.
Is TEAS chemistry hard without a chemistry class?
It is high-school level. If you haven't had chemistry, the tables on this page plus a free textbook such as OpenStax Chemistry cover what the questions draw on; give it the 10 days in the plan.
Sources
- ATI, ATI TEAS exam details (science questions, minutes, content areas). Read for our format guide, October 2026.
- ATI, ATI TEAS Version 7 content outline (the six chemistry objectives).
- OpenStax, Chemistry 2e, Rice University: atomic structure, periodic trends, bonding, reactions, solutions, acids and bases.
- OpenStax, Anatomy and Physiology 2e: blood pH range and buffers, enzymes, tonicity.
- Open Exam Prep, TEAS chemistry basics: topic list. Read 2026-11-02.
More science guides: TEAS anatomy and physiology, how to study for the TEAS science section, the TEAS science practice test, or all guides. To find out where chemistry stands against your other sections, take the free practice test: 15 questions, scored against your program's minimum.