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Question 1Processes of Science (scientific method, experimental design, data interpretation)

A student wonders whether adding sugar to water makes it boil at a higher temperature. Which statement is the best testable hypothesis?

  1. Boiling water looks like it is moving a lot.
  2. Water boils when it gets hot enough.
  3. Adding sugar to water raises its boiling point. Correct answer.
  4. Sugar tastes sweet when dissolved in water.

Explanation

A testable hypothesis is a specific, falsifiable prediction linking a manipulated variable to a measurable outcome. Saying that adding sugar raises the boiling point predicts a measurable change in temperature. The other statements are general observations that cannot be tested against a predicted result.

Question 2Processes of Science (scientific method, experimental design, data interpretation)

In an experiment testing whether fertilizer affects plant growth, which is the independent variable?

  1. The type of soil used for all plants
  2. The amount of fertilizer given Correct answer.
  3. The number of leaves on each plant
  4. The height of the plants after four weeks

Explanation

The independent variable is the factor deliberately changed or set by the experimenter. Here the amount of fertilizer is what the researcher manipulates. Plant height and leaf number are measured outcomes, and the soil type is held constant.

Question 3Processes of Science (scientific method, experimental design, data interpretation)

Why do scientists usually include a control group in an experiment?

  1. To guarantee that the results will be statistically significant
  2. To provide a baseline for comparing the effect of the treatment Correct answer.
  3. To make sure the experiment finishes more quickly
  4. To increase the total number of measurements taken

Explanation

A control group is treated the same as the experimental group except for the independent variable. This gives a baseline showing what would happen without the treatment. Comparing the two groups lets researchers attribute any difference to the manipulated variable.

Question 4Processes of Science (scientific method, experimental design, data interpretation)

A student measures the mass of the same object three times and gets 12.1 g, 12.0 g, and 12.1 g. The true mass is 15.0 g. Which statement best describes these measurements?

  1. They are neither accurate nor precise.
  2. They are precise but not accurate. Correct answer.
  3. They are both accurate and precise.
  4. They are accurate but not precise.

Explanation

Precision refers to how closely repeated measurements agree with each other, while accuracy refers to how close they are to the true value. The three readings are tightly clustered, so they are precise. They are far from 15.0 g, so they are not accurate.

Question 5Processes of Science (scientific method, experimental design, data interpretation)

Which action is the best way to reduce the effect of random measurement error on an experiment's results?

  1. Record only the measurements closest to the expected value
  2. Use a different measuring tool for each trial
  3. Repeat the measurements several times and average them Correct answer.
  4. Round every measurement to the nearest whole number

Explanation

Random errors scatter above and below the true value, so repeating measurements and averaging tends to cancel them out. Rounding or discarding data does not remove the underlying scatter. Changing tools between trials adds new variation instead of reducing it.

Question 6Processes of Science (scientific method, experimental design, data interpretation)

A graph shows that as the temperature of a gas increases, its volume also increases in a steady, proportional way. What relationship does the graph show?

  1. No relationship at all
  2. A positive linear relationship Correct answer.
  3. An inverse relationship
  4. A cyclical relationship

Explanation

When both variables increase together and the points form a straight line, the graph shows a positive linear relationship. An inverse relationship would show one variable decreasing as the other increases. A lack of relationship would appear as scattered points with no trend.

Question 7Processes of Science (scientific method, experimental design, data interpretation)

A researcher wants to know whether a new drug lowers blood pressure. Which design best tests this question?

  1. Ask doctors whether they think the drug works
  2. Measure blood pressure in people who already take the drug
  3. Give the drug to one group and a placebo to a similar group, then compare blood pressure Correct answer.
  4. Give the drug to volunteers and ask them how they feel

Explanation

A controlled comparison with a placebo group isolates the drug's effect from other influences such as expectation. Measuring blood pressure provides an objective outcome. The other approaches lack a comparison group or rely on opinion rather than measurement.

Question 8Processes of Science (scientific method, experimental design, data interpretation)

A student tests how light intensity affects the rate of photosynthesis in pondweed. Which variable must be held constant to make the comparison fair?

  1. The temperature of the water Correct answer.
  2. The number of bubbles counted per minute
  3. The distance of the lamp from the plant
  4. The rate of bubble production

Explanation

Controlled variables are factors kept the same so they cannot affect the outcome. Temperature strongly affects enzyme activity and therefore photosynthesis, so it must be held constant. Bubble production rate is the dependent variable, and light distance is the independent variable being changed.

Question 9Processes of Science (scientific method, experimental design, data interpretation)

Two groups of 30 students each study the same material. Group A studies in silence, and Group B studies with music. Both take the same test the next day. What is the most important reason for using 30 students per group rather than one?

  1. Larger groups make the test questions easier
  2. Larger groups guarantee that the hypothesis is correct
  3. Larger groups reduce the influence of individual differences on the results Correct answer.
  4. Larger groups remove the need for a control group

Explanation

Individual differences in ability and motivation can mask or exaggerate a treatment effect. Using many participants averages out these individual variations. A larger sample gives a more reliable estimate of the group effect, though it never guarantees a conclusion.

Question 10Processes of Science (scientific method, experimental design, data interpretation)

A scientist reports that a fertilizer increased average crop yield by 12 percent, with a margin of error of plus or minus 3 percent. How should this result be interpreted?

  1. The result is invalid because averages cannot be reported
  2. The true increase is likely somewhere near 12 percent, within about 3 percent Correct answer.
  3. The fertilizer had no effect because of the margin of error
  4. The fertilizer definitely increased yield by exactly 12 percent

Explanation

A margin of error expresses the uncertainty around an estimated value. The reported increase of 12 percent should be read as an estimate that probably lies within about 3 percent of that figure. Reporting uncertainty is a normal and honest part of scientific communication.

Question 11Processes of Science (scientific method, experimental design, data interpretation)

A student claims that plants grow faster when spoken to because the spoken-to plant grew 2 cm more than the other. Both plants sat on the same windowsill, but the spoken-to plant was in a larger pot. What is the most likely flaw in the conclusion?

  1. The windowsill was too bright for the plants
  2. The student measured growth in centimetres instead of millimetres
  3. Two plants are too many for an experiment
  4. The pot size was not controlled and could explain the difference Correct answer.

Explanation

For a fair test, all variables except the one being tested must be kept the same. Pot size can affect root space and water availability, so it is a confounding variable. The observed difference could be caused by pot size rather than by being spoken to.

Question 12Processes of Science (scientific method, experimental design, data interpretation)

A table lists the following results for a reaction at different temperatures: 10 degrees C gives 5 s, 20 degrees C gives 4 s, 30 degrees C gives 3 s, 40 degrees C gives 2 s. Which conclusion is best supported?

  1. Reaction time is unrelated to the reaction
  2. Temperature has no effect on reaction time
  3. Reaction time increases as temperature increases
  4. Reaction time decreases as temperature increases Correct answer.

Explanation

Reading the table, the time drops steadily from 5 s to 2 s as temperature rises from 10 to 40 degrees C. This shows a consistent decrease in reaction time with increasing temperature. Conclusions should follow the trend shown by the data, not an assumed relationship.

Question 13Processes of Science (scientific method, experimental design, data interpretation)

In a fair test of how exercise affects heart rate, which pair correctly identifies the dependent and controlled variables?

  1. Dependent: heart rate; controlled: duration of exercise Correct answer.
  2. Dependent: duration of exercise; controlled: heart rate
  3. Dependent: amount of exercise; controlled: heart rate
  4. Dependent: heart rate; controlled: the hypothesis

Explanation

The dependent variable is the outcome measured in response to the change, which is heart rate. Controlled variables are factors kept fixed, such as the duration of exercise, so they do not distort the comparison. The amount of exercise is the independent variable.

Question 14Processes of Science (scientific method, experimental design, data interpretation)

A researcher finds that towns with more ice-cream sales also have more cases of sunburn. Which conclusion is most reasonable?

  1. Sunburn causes people to buy ice cream
  2. Eating ice cream causes sunburn
  3. A third factor such as hot sunny weather likely links both Correct answer.
  4. The two observations are completely unrelated

Explanation

Correlation between two variables does not prove that one causes the other. A lurking variable, such as hot sunny weather, can independently drive both ice-cream sales and sunburn. The data support an association, and a common cause is the most reasonable explanation.

Question 15Processes of Science (scientific method, experimental design, data interpretation)

A student writes a conclusion that states, "My results prove the hypothesis is true." Why is this wording a problem in scientific reporting?

  1. Results support or fail to support a hypothesis rather than proving it Correct answer.
  2. Results should be kept secret until they are certain
  3. Conclusions should only describe the method used
  4. Conclusions should never mention the hypothesis

Explanation

Scientific conclusions are provisional and based on evidence, so data can support a hypothesis but rarely prove it absolutely. New evidence could later require revision. Careful wording reflects the limits of what the data can show.

Question 16Processes of Science (scientific method, experimental design, data interpretation)

A graph plots distance travelled against time for a moving toy car, and the points form a straight line through the origin. What does the slope of this line represent?

  1. The total time of the journey
  2. The mass of the toy car
  3. The starting position of the car
  4. The speed of the toy car Correct answer.

Explanation

On a distance-time graph, the slope equals the change in distance divided by the change in time. That ratio is speed. A straight line through the origin shows constant speed.

Question 17Processes of Science (scientific method, experimental design, data interpretation)

A team tests a new insulating material by placing equal masses of hot water in identical cups, one wrapped in the material and one unwrapped. They record the temperature every minute for 20 minutes. Which result would most strongly support the claim that the material insulates well?

  1. Both cups cool at exactly the same rate
  2. The wrapped cup cools more slowly than the unwrapped cup Correct answer.
  3. The wrapped cup cools faster than the unwrapped cup
  4. Both cups reach room temperature within one minute

Explanation

Good insulation slows heat loss, so the insulated cup should keep its temperature longer than the control cup. Comparing the cooling rates of identical setups isolates the material's effect. Faster or equal cooling would not support the claim.

Question 18Processes of Science (scientific method, experimental design, data interpretation)

A student collects data on seed germination at four temperatures and finds the highest germination at 25 degrees C. Which additional step would most strengthen the conclusion that 25 degrees C is optimal?

  1. Discarding the trials that gave lower germination
  2. Changing the type of seeds used in each trial
  3. Repeating only the 25 degrees C trial many times
  4. Testing more temperatures close to 25 degrees C to see if germination is even higher Correct answer.

Explanation

To claim an optimum, the peak must be shown to be a true maximum rather than just the highest of the tested points. Testing temperatures just above and below 25 degrees C checks whether germination rises further nearby. Repeating only one condition cannot locate a peak.

Question 19Processes of Science (scientific method, experimental design, data interpretation)

Two studies examine the same question. Study A uses 500 participants and finds a small effect. Study B uses 8 participants and finds a large effect. Which statement about these studies is most reasonable?

  1. Study B is more reliable because its effect is larger
  2. Neither study can be trusted because the results differ
  3. Study A is generally more reliable because of its larger sample Correct answer.
  4. Both studies are equally reliable because both found an effect

Explanation

Larger samples generally give more stable estimates and reduce the influence of chance variation. A dramatic effect in a very small sample is more likely to be a fluke. Differing results are normal and call for careful comparison, not automatic dismissal.

Question 20Processes of Science (scientific method, experimental design, data interpretation)

A researcher predicts that a catalyst will speed up a reaction. The data show the reaction time is unchanged with and without the catalyst. What is the most appropriate scientific response?

  1. Conclude that the catalyst works but the effect was too small to see
  2. Report that the hypothesis was not supported and consider why Correct answer.
  3. Abandon the entire line of research immediately
  4. Change the recorded data so they match the prediction

Explanation

A hypothesis is a testable prediction, and evidence that contradicts it should be reported honestly. The next step is to examine possible reasons, such as the catalyst being unsuitable or the measurement being too crude. Altering data or inventing unseen effects violates scientific integrity.

Question 21Chemistry: Atoms, Elements, and the Periodic Table

Which subatomic particle carries a negative charge and orbits the nucleus?

  1. Nucleus
  2. Electron Correct answer.
  3. Proton
  4. Neutron

Explanation

Electrons are the negatively charged particles found outside the nucleus in the electron cloud. Protons are positive and neutrons are neutral, and both reside in the nucleus. The nucleus itself is the central core, not a particle.

Question 22Chemistry: Atoms, Elements, and the Periodic Table

An atom of chlorine has an atomic number of 17 and a mass number of 35. How many neutrons does this atom contain?

  1. 52
  2. 18 Correct answer.
  3. 35
  4. 17

Explanation

The number of neutrons equals the mass number minus the atomic number, so 35 minus 17 gives 18 neutrons. The atomic number counts protons only, and the mass number is the total of protons and neutrons.

Question 23Chemistry: Atoms, Elements, and the Periodic Table

In the periodic table, elements in the same vertical column are called a group. What do elements in the same group share?

  1. The same number of electron shells
  2. The same atomic mass
  3. The same number of valence electrons Correct answer.
  4. The same number of neutrons

Explanation

Elements in a group have the same number of electrons in their outermost shell, which gives them similar chemical properties. The number of shells increases as you move down a group, and neutron counts vary between elements.

Question 24Chemistry: Atoms, Elements, and the Periodic Table

Which statement best describes a compound?

  1. A mixture of two elements that can be separated by filtering
  2. A single element in its purest form
  3. A substance made of two or more elements chemically bonded in a fixed ratio Correct answer.
  4. A solution in which one substance dissolves in another

Explanation

A compound forms when atoms of different elements bond chemically, producing a substance with a fixed composition and new properties. Mixtures and solutions can be separated physically and do not have a fixed ratio.

Question 25Chemistry: Atoms, Elements, and the Periodic Table

Which of the following is a noble gas located in Group 18 of the periodic table?

  1. Calcium
  2. Chlorine
  3. Sodium
  4. Argon Correct answer.

Explanation

Argon belongs to Group 18, the noble gases, which have full outer electron shells and are largely unreactive. Sodium and calcium are metals in other groups, and chlorine is a halogen in Group 17.

Question 26Chemistry: Atoms, Elements, and the Periodic Table

Which particle arrangement best describes a solid?

  1. Particles far apart and moving quickly in all directions
  2. Particles closely packed in fixed positions that vibrate Correct answer.
  3. Particles spread out with no regular arrangement
  4. Particles close together but free to slide past one another

Explanation

In a solid, particles are held closely together in a regular arrangement and can only vibrate about fixed positions. Sliding particles describe a liquid, and fast, widely spaced particles describe a gas.

Question 27Chemistry: Atoms, Elements, and the Periodic Table

Which of the following is a chemical change rather than a physical change?

  1. Water boiling into steam
  2. Iron rusting in moist air Correct answer.
  3. Ice melting into water
  4. Sugar dissolving in water

Explanation

Rusting produces a new substance, iron oxide, so it is a chemical change that cannot be easily reversed. Melting, dissolving, and boiling only alter the state or arrangement of the same substance.

Question 28Chemistry: Atoms, Elements, and the Periodic Table

An atom has 11 protons, 12 neutrons, and 11 electrons. What is its mass number?

  1. 12
  2. 23 Correct answer.
  3. 11
  4. 34

Explanation

The mass number is the sum of protons and neutrons, so 11 plus 12 equals 23. Electrons are far lighter and are not counted in the mass number.

Question 29Chemistry: Atoms, Elements, and the Periodic Table

An atom of an element has the electron configuration 2, 8, 7. In which group of the periodic table does this element most likely belong?

  1. Group 15
  2. Group 1
  3. Group 7
  4. Group 17 Correct answer.

Explanation

The element has seven valence electrons in its outer shell, which places it in Group 17, the halogens. Group number and valence electron count are related for the main-group elements on the right side of the table.

Question 30Chemistry: Atoms, Elements, and the Periodic Table

Two atoms are isotopes of the same element. Which statement must be true about them?

  1. They have the same number of neutrons but different protons
  2. They have the same number of protons but different neutrons Correct answer.
  3. They have different numbers of both protons and neutrons
  4. They have the same mass number but different atomic numbers

Explanation

Isotopes are atoms of the same element, so they share the same number of protons but differ in their neutron count. This gives them different mass numbers while the atomic number stays the same.

Question 31Chemistry: Atoms, Elements, and the Periodic Table

Which list correctly orders the elements sodium, chlorine, and argon by increasing reactivity as a general trend across Period 3?

  1. Argon, sodium, chlorine Correct answer.
  2. Sodium, argon, chlorine
  3. Chlorine, sodium, argon
  4. Argon, chlorine, sodium

Explanation

Argon is a noble gas with a full outer shell and is essentially unreactive. Sodium is a reactive metal, and chlorine is a very reactive non-metal, so reactivity generally rises from the noble gas toward the reactive halogen.

Question 32Chemistry: Atoms, Elements, and the Periodic Table

What happens to the particles of a liquid when it evaporates?

  1. They combine chemically to form a new compound
  2. They break apart into protons and neutrons
  3. They lose energy and lock into fixed positions
  4. They gain enough energy to escape into the gas state Correct answer.

Explanation

Evaporation occurs when particles at the surface gain enough kinetic energy to overcome attractive forces and enter the gas state. This is a change of state, not a chemical reaction, so particles keep their identity.

Question 33Chemistry: Atoms, Elements, and the Periodic Table

A pure substance is found to be a good conductor of electricity when solid and has a very high melting point. Which type of substance is it most likely to be?

  1. A metal Correct answer.
  2. A non-metal element
  3. A noble gas
  4. A molecular compound

Explanation

Metals conduct electricity in the solid state because of delocalized electrons and generally have high melting points. Molecular compounds and noble gases typically do not conduct in the solid state.

Question 34Chemistry: Atoms, Elements, and the Periodic Table

Which statement correctly describes the arrangement of the modern periodic table?

  1. Elements are ordered by increasing neutron number
  2. Elements are ordered by decreasing atomic mass
  3. Elements are ordered alphabetically by symbol
  4. Elements are ordered by increasing atomic number Correct answer.

Explanation

The modern periodic table arranges elements in order of increasing atomic number, which is the number of protons. This ordering corrected earlier tables that used atomic mass and placed some elements incorrectly.

Question 35Chemistry: Atoms, Elements, and the Periodic Table

An ion of magnesium has a 2+ charge. What has happened to a neutral magnesium atom to form this ion?

  1. It lost two electrons Correct answer.
  2. It gained two neutrons
  3. It lost two neutrons
  4. It gained two protons

Explanation

A positive ion forms when an atom loses electrons, so a 2+ magnesium ion has lost two electrons. Protons are not gained or lost in ordinary ion formation, and neutrons do not affect charge.

Question 36Chemistry: Atoms, Elements, and the Periodic Table

Which pair of elements would most likely form an ionic compound when combined?

  1. Two non-metals such as oxygen and chlorine
  2. A metal and a non-metal such as sodium and chlorine Correct answer.
  3. Two metals such as sodium and magnesium
  4. Two noble gases such as helium and neon

Explanation

Ionic bonds form when a metal transfers electrons to a non-metal, creating oppositely charged ions that attract. Two non-metals usually share electrons to form covalent bonds instead.

Question 37Chemistry: Atoms, Elements, and the Periodic Table

Which observation provides the best evidence that a chemical reaction has occurred?

  1. A gas is produced as bubbles when two solutions are mixed Correct answer.
  2. A solid dissolves and the liquid becomes clear
  3. A white powder is ground into a finer powder
  4. A liquid is heated and begins to boil

Explanation

Bubbles of a new gas forming when two solutions mix indicate a new substance is being produced, a sign of chemical change. Dissolving, boiling, and grinding are physical changes that do not create new substances.

Question 38Chemistry: Atoms, Elements, and the Periodic Table

A sample contains atoms with 6 protons and 6 neutrons, and another sample contains atoms with 6 protons and 7 neutrons. What are these two types of atoms called?

  1. Different elements
  2. Compounds of carbon
  3. Ions of carbon
  4. Isotopes of carbon Correct answer.

Explanation

Both types of atoms have six protons, so they are the same element, carbon, but they differ in neutron count. Atoms of the same element with different neutron numbers are isotopes.

Question 39Chemistry: Atoms, Elements, and the Periodic Table

Which statement best explains why noble gases are generally unreactive?

  1. They have only one valence electron
  2. They are all metals
  3. They have a full outer electron shell Correct answer.
  4. They are all radioactive

Explanation

Noble gases have complete outer shells, so they do not need to gain or lose electrons to become stable. This stable configuration makes them chemically inert under ordinary conditions.

Question 40Chemistry: Atoms, Elements, and the Periodic Table

Which property generally increases as you move from left to right across a period in the periodic table?

  1. Metallic character
  2. Atomic radius
  3. Electronegativity Correct answer.
  4. Number of electron shells

Explanation

Across a period, added protons pull electrons more strongly, so electronegativity generally increases from left to right. Atomic radius and metallic character tend to decrease in the same direction.

Question 41Chemistry: Atoms, Elements, and the Periodic Table

A neutral atom has an electron configuration of 2, 8, 8, 1. Which group and period does this element belong to?

  1. Group 4, Period 1
  2. Group 8, Period 3
  3. Group 18, Period 4
  4. Group 1, Period 4 Correct answer.

Explanation

The single valence electron places the element in Group 1, and the four occupied shells place it in Period 4. The period number equals the number of electron shells, and the group relates to the valence electrons.

Question 42Chemistry: Atoms, Elements, and the Periodic Table

A certain element forms a 1- ion, and its atoms contain 17 protons. Which element is it?

  1. Sodium
  2. Chlorine Correct answer.
  3. Argon
  4. Potassium

Explanation

The atomic number 17 identifies the element as chlorine, a halogen that gains one electron to form a 1- ion. Sodium and potassium are metals that form positive ions, and argon is a noble gas.

Question 43Chemistry: Atoms, Elements, and the Periodic Table

Why does the mass number of an atom ignore the mass of its electrons?

  1. Electrons have no mass at all
  2. Electrons change into neutrons over time
  3. Electrons are much lighter than protons and neutrons Correct answer.
  4. Electrons are found only in the nucleus

Explanation

An electron has a mass roughly 1800 times smaller than a proton or neutron, so its contribution to atomic mass is negligible. The mass number therefore counts only protons and neutrons.

Question 44Chemistry: Atoms, Elements, and the Periodic Table

An unknown substance does not conduct electricity when solid but conducts when dissolved in water, and it forms a crystal lattice. Which classification best fits this substance?

  1. An ionic compound Correct answer.
  2. A metal
  3. A covalent molecular gas
  4. A noble gas

Explanation

Ionic compounds form crystal lattices and do not conduct as solids because ions are fixed, but their ions move freely when dissolved, allowing conduction. Metals conduct as solids, and molecular gases do not form such lattices.

Question 45Chemistry: Chemical Reactions and Conservation of Mass

In a chemical reaction, which statement best describes what happens to the total mass of the reactants and products in a closed system?

  1. The total mass increases because new atoms are created
  2. The total mass stays the same because atoms are only rearranged Correct answer.
  3. The total mass decreases because some matter is converted to energy
  4. The total mass changes depending on the temperature of the reaction

Explanation

The law of conservation of mass states that matter cannot be created or destroyed in a chemical reaction. Atoms are simply rearranged into new combinations, so the total mass of reactants equals the total mass of products in a closed system.

Question 46Chemistry: Chemical Reactions and Conservation of Mass

Which of the following is a correct balanced chemical equation for the reaction of hydrogen gas with oxygen gas to form water?

  1. H2 + O2 → 2H2O
  2. H2 + O2 → H2O
  3. 2H2 + O2 → 2H2O Correct answer.
  4. 2H2 + 2O2 → 2H2O

Explanation

A balanced equation must have equal numbers of each type of atom on both sides. Two hydrogen molecules and one oxygen molecule give four hydrogen atoms and two oxygen atoms, matching two water molecules.

Question 47Chemistry: Chemical Reactions and Conservation of Mass

Which observation is the strongest evidence that a chemical reaction has occurred rather than a physical change?

  1. A new gas forms and the temperature rises sharply Correct answer.
  2. A liquid is heated and begins to boil
  3. A solid dissolves and the mixture becomes clear
  4. A substance is ground into a fine powder

Explanation

Formation of a new substance, such as a gas that was not present before, together with an energy change like a sharp temperature rise, indicates a chemical reaction. Physical changes alter form or state without producing new substances.

Question 48Chemistry: Chemical Reactions and Conservation of Mass

In the formula for calcium carbonate, CaCO3, how many oxygen atoms are present in one formula unit?

  1. 6
  2. 2
  3. 1
  4. 3 Correct answer.

Explanation

A subscript in a chemical formula tells how many atoms of the preceding element are in one formula unit. The subscript 3 after the O indicates three oxygen atoms.

Question 49Chemistry: Chemical Reactions and Conservation of Mass

Which type of reaction is represented by the equation 2Na + Cl2 → 2NaCl?

  1. Single replacement
  2. Decomposition
  3. Combustion
  4. Synthesis Correct answer.

Explanation

In a synthesis reaction, two or more simpler substances combine to form a single more complex product. Here sodium and chlorine combine into one compound, sodium chloride.

Question 50Chemistry: Chemical Reactions and Conservation of Mass

What does the symbol (aq) after a chemical formula indicate?

  1. The substance is a pure liquid
  2. The substance is a gas at room temperature
  3. The substance is a solid precipitate
  4. The substance is dissolved in water Correct answer.

Explanation

The state symbol (aq) means aqueous, indicating that the substance is dissolved in water. It distinguishes a dissolved species from a pure liquid, which is shown as (l).