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TEAS chemistry practice questions

Free TEAS-style chemistry questions: atoms and the periodic table, states of matter, bonds and balanced equations, reaction rates, solutions, and acids, bases and pH.

Tap an answer to check it, or open "Show the answer and rationale" under each question.

Question 1 of 10 · Chemistry

As the pH of a solution increases from 8 to 12, what happens to its ion concentrations?

  1. H⁺ and OH⁻ are unchanged.
  2. H⁺ and OH⁻ each increase.
  3. H⁺ decreases and OH⁻ increases.
  4. H⁺ increases and OH⁻ decreases.
Show the answer and rationale

Answer: C

A higher pH means fewer hydrogen ions and more hydroxide ions; the two change in opposite directions. H⁺ rising would lower the pH, and the two concentrations cannot both rise or both stay fixed while the pH changes.

📚 Learn it: Acids, bases, pH and buffers

Question 2 of 10 · Chemistry

A stomach fluid sample has a pH of 2, and a saliva sample has a pH of 5. The stomach fluid has how many times the hydrogen ion concentration of the saliva?

  1. 30 times
  2. 3 times
  3. 100 times
  4. 1,000 times
Show the answer and rationale

Answer: D

The difference is 5 − 2 = 3 pH units, and each unit multiplies H⁺ by 10: 10 × 10 × 10 = 1,000. Three treats the scale as linear, 30 multiplies 3 by 10, and 100 corresponds to only two units.

Step by step

  1. Difference in pH = 5 − 2 = 3 units.
  2. 10³ = 10 × 10 × 10 = 1,000.
  3. The stomach fluid has 1,000 times the H⁺ concentration of the saliva.

📚 Learn it: Acids, bases, pH and buffers

Question 3 of 10 · Chemistry

Droplets of water form on the outside of a glass of ice water on a humid day. Which process causes this?

  1. Evaporation
  2. Condensation
  3. Melting
  4. Sublimation
Show the answer and rationale

Answer: B

Water vapor in the air cools when it touches the cold glass and changes from gas to liquid, which is condensation. The water is not leaking through the glass; evaporation is liquid to gas, sublimation is solid to gas, and melting is solid to liquid.

📚 Learn it: States of matter and physical vs chemical change

Question 4 of 10 · Chemistry

A red blood cell is placed in a solution with a much higher concentration of dissolved particles than the cell's cytoplasm. What happens?

  1. Nothing, because water cannot cross membranes.
  2. Water enters and the cell swells.
  3. Water leaves and the cell shrinks.
  4. Solute enters until the cell bursts.
Show the answer and rationale

Answer: C

In a hypertonic solution water moves by osmosis toward the higher particle concentration, out of the cell, so it shrinks (crenates). The cell swells only in a hypotonic solution, and water crosses cell membranes freely; the membrane mostly blocks the solute, not the water.

📚 Learn it: Solutions, concentration and dilution

Question 5 of 10 · Chemistry

Heating a sample of ice at a steady rate
Time (min)Temperature (°C)
0−20
2−10
40
60
80
1010
1220

Based on the table, what is happening to the sample between minutes 4 and 8?

  1. The ice is warming without changing state.
  2. The ice is melting while its temperature stays constant.
  3. The water is boiling into vapor at its boiling point.
  4. The heat source was turned off.
Show the answer and rationale

Answer: B

The temperature holds at 0 °C, the melting point of ice, because the added energy is breaking the solid structure rather than raising temperature. Warming without a state change would show rising temperature, boiling happens at 100 °C, and the heat source must still be on because the temperature rises again after minute 8.

📚 Learn it: States of matter and physical vs chemical change

Question 6 of 10 · Chemistry

Adding more water to a salt solution changes which of the following?

  1. The mass of salt present
  2. The chemical formula of the salt
  3. The concentration of the solution
  4. The number of salt ions present
Show the answer and rationale

Answer: C

Adding solvent spreads the same amount of solute through a larger volume, so concentration decreases. The mass of salt and the number of its ions stay the same, and dissolving or diluting does not change the salt's chemical formula.

📚 Learn it: Solutions, concentration and dilution

Question 7 of 10 · Chemistry

The periodic table lists the atomic mass of chlorine as 35.45 rather than a whole number. Why?

  1. The value is rounded from the atomic number.
  2. Electrons add a large and variable amount of mass to each chlorine atom.
  3. It is a weighted average of chlorine's naturally occurring isotopes.
  4. Some chlorine atoms have a fraction of a proton.
Show the answer and rationale

Answer: C

Natural chlorine is a mix of mostly chlorine-35 and some chlorine-37, and the listed atomic mass is the average weighted by how common each isotope is. Particles cannot be fractional, electrons add very little mass, and the atomic number is 17, not 35.

📚 Learn it: Atomic structure and the periodic table

Question 8 of 10 · Chemistry

A neutral oxygen atom has 8 electrons. If its first shell holds 2 electrons, how many valence electrons does oxygen have?

  1. 4
  2. 6
  3. 8
  4. 2
Show the answer and rationale

Answer: B

The first shell holds 2 electrons, leaving 8 − 2 = 6 in the second (outer) shell, so oxygen has 6 valence electrons and tends to gain 2 more. Eight is the total electron count, and 2 is the inner shell, not the valence shell.

Step by step

  1. Total electrons = 8.
  2. First shell holds 2.
  3. Outer shell = 8 − 2 = 6 valence electrons.

📚 Learn it: Atomic structure and the periodic table

Question 9 of 10 · Chemistry

Zinc pieces of equal size in hydrochloric acid at 25 °C
Acid concentration (mol/L)Time to collect 20 mL of gas (s)
0.5160
1.080
2.040

What conclusion is best supported by the data?

  1. Doubling the acid concentration roughly halves the time.
  2. Higher temperature slows the reaction.
  3. The zinc acts as a catalyst.
  4. Acid concentration has no measurable effect on the reaction rate.
Show the answer and rationale

Answer: A

Each time the concentration doubles (0.5 to 1.0 to 2.0), the time halves (160 to 80 to 40 s), so the rate rises with concentration because particles collide more often. Temperature was held at 25 °C, the data clearly show an effect, and zinc is a reactant that is used up, not a catalyst.

📚 Learn it: Reaction types and what changes reaction rates

Question 10 of 10 · Chemistry

Time for 2 g of chalk to react completely in the same acid
Form of chalkTime (s)
One solid stick300
Four small chunks140
Fine powder35

Which factor best explains the results in the table?

  1. Concentration of the acid
  2. Temperature of the acid
  3. Surface area of the chalk
  4. Use of a catalyst
Show the answer and rationale

Answer: C

The mass of chalk and the acid are the same in every trial; only the size of the pieces changes. Smaller pieces expose more surface area, so more particles meet the acid at once and the reaction finishes faster. Acid concentration, temperature and catalysts were not changed.

📚 Learn it: Reaction types and what changes reaction rates

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