Question 1:

Let's evaluate each option:

A. Mixtures have a fixed composition – This is false. Mixtures can have varying compositions (e.g., saltwater can have different amounts of salt).

B. Differences in physical properties are used to separate components of a mixture – This is true. For example, filtration uses differences in particle size, distillation uses differences in boiling points, and chromatography uses differences in solubility or adhesion.

C. The components in a mixture are chemically combined – This is false. In a mixture, the components are physically combined and can be separated by physical means. Chemical combinations occur in compounds, not mixtures.

D. Mixtures can be represented by a chemical formula – This is false. Only pure substances (elements and compounds) have chemical formulas. Mixtures do not have a fixed ratio of components and thus cannot be represented by a single formula.

Therefore, the correct statement is B.

*These A.I. responses have been individually checked to ensure they match the accepted answer, but explanations may still be incorrect. Responses may give guidance but the A.I. might not be able to answer the question! This is particularly the case for questions based on diagrams, which the A.I. typically cannot interpret.
Grade Gorilla uses Gemini, Deepseek and a range of other A.I. chatbots to generate the saved responses. Some answers have had human intervention for clarity or where the A.I. has not been able to answer the question.

Question 2:

Let's evaluate each option to determine which is NOT a homogeneous mixture:

• A homogeneous mixture has a uniform composition and properties throughout (e.g., saltwater, air).

• A heterogeneous mixture has non-uniform composition, with visible differences or phases (e.g., oil and water, sand and water).

A. Oil and water – This is a heterogeneous mixture. Oil and water do not mix uniformly; they separate into distinct layers due to differences in polarity and density.

B. Stainless steel – This is a homogeneous mixture (specifically, a solid solution). It is an alloy of iron, carbon, chromium, and other elements, with a uniform composition.

C. Ethanol and water – This is a homogeneous mixture. Ethanol and water are miscible and form a uniform solution.

D. Unpolluted air – This is a homogeneous mixture. Air is a uniform mixture of gases (mainly nitrogen, oxygen, argon, etc.).

Therefore, the option that is NOT a homogeneous mixture is A. oil and water.

*These A.I. responses have been individually checked to ensure they match the accepted answer, but explanations may still be incorrect. Responses may give guidance but the A.I. might not be able to answer the question! This is particularly the case for questions based on diagrams, which the A.I. typically cannot interpret.
Grade Gorilla uses Gemini, Deepseek and a range of other A.I. chatbots to generate the saved responses. Some answers have had human intervention for clarity or where the A.I. has not been able to answer the question.

Question 4:

To determine which amino acid has an Rf value of 0.5, we need to calculate the Rf value for each amino acid and compare it to 0.5.

The Rf (retardation factor) value is calculated using the formula:

Given:

• Solvent front = 7 cm

• Acid A travelled = 6 cm

• Acid B travelled = 4.5 cm

• Acid C travelled = 3.5 cm

• Acid D travelled = 2.5 cm

Now, calculate the Rf value for each amino acid:

For Acid A:

For Acid B:

For Acid C:

For Acid D:

From the calculations, Acid C has an Rf value of exactly 0.5.

Answer: Acid C has an Rf value of 0.5.

*These A.I. responses have been individually checked to ensure they match the accepted answer, but explanations may still be incorrect. Responses may give guidance but the A.I. might not be able to answer the question! This is particularly the case for questions based on diagrams, which the A.I. typically cannot interpret.
Grade Gorilla uses Gemini, Deepseek and a range of other A.I. chatbots to generate the saved responses. Some answers have had human intervention for clarity or where the A.I. has not been able to answer the question.

Question 5:

Let's evaluate each option to determine which statement correctly describes a compound:

• A. A compound consists of atoms of the same element.
  This is incorrect. A compound is made up of atoms of two or more different elements chemically bonded together. Substances made of the same element are allotropes or elemental forms (e.g., O₂, O₃), not compounds.

• B. In a compound, the elements are physically bonded together.
  This is incorrect. In a compound, elements are chemically bonded (e.g., covalent or ionic bonds), not physically bonded. Physical bonds (like van der Waals forces) are typical in mixtures, not compounds.

• C. In a compound, the elements are present in a fixed ratio.
  This is correct. Compounds have a definite and constant composition, meaning the elements are combined in fixed proportions by mass (e.g., water is always H₂O, with 2:1 hydrogen to oxygen ratio).

• D. The elements in a compound can be separated by physical methods.
  This is incorrect. Physical methods (like filtration or distillation) can separate mixtures but not compounds. Breaking down a compound requires chemical methods (e.g., electrolysis to break water into hydrogen and oxygen).

The correct statement is C: In a compound, the elements are present in a fixed ratio.

*These A.I. responses have been individually checked to ensure they match the accepted answer, but explanations may still be incorrect. Responses may give guidance but the A.I. might not be able to answer the question! This is particularly the case for questions based on diagrams, which the A.I. typically cannot interpret.
Grade Gorilla uses Gemini, Deepseek and a range of other A.I. chatbots to generate the saved responses. Some answers have had human intervention for clarity or where the A.I. has not been able to answer the question.

Question 6:

To determine at which temperature bromine is a liquid, we need to consider its melting and boiling points:

• Melting point: -7.05°C

• Boiling point: 58.8°C

Bromine is in the liquid state between these two temperatures. That is, above -7.05°C and below 58.8°C.

Now, we need to check which of the given options (in Kelvin) falls within this range. First, convert the melting and boiling points to Kelvin:

• Melting point in K:
  -7.05°C + 273 = 265.95 K (approximately 266 K)

• Boiling point in K:
  58.8°C + 273 = 331.8 K (approximately 332 K)

So, bromine is a liquid between about 266 K and 332 K.

Now, evaluate the options:

• A. 200 K → Below 266 K (solid)

• B. 250 K → Below 266 K (solid)

• C. 300 K → Between 266 K and 332 K (liquid)

• D. 350 K → Above 332 K (gas)

Therefore, at 300 K, bromine is a liquid.

Answer: C. 300 K

*These A.I. responses have been individually checked to ensure they match the accepted answer, but explanations may still be incorrect. Responses may give guidance but the A.I. might not be able to answer the question! This is particularly the case for questions based on diagrams, which the A.I. typically cannot interpret.
Grade Gorilla uses Gemini, Deepseek and a range of other A.I. chatbots to generate the saved responses. Some answers have had human intervention for clarity or where the A.I. has not been able to answer the question.

Question 7:

The equation given is:

This represents a direct change from a gas to a solid without passing through the liquid state. This process is known as deposition.

Now, let's review the options:

• A. Condensation: This is the change from gas to liquid (e.g., water vapor to liquid water).

• B. Deposition: This is the change directly from gas to solid (e.g., frost forming from water vapor).

• C. Freezing: This is the change from liquid to solid (e.g., liquid water to ice).

• D. Sublimation: This is the change from solid to gas (e.g., dry ice (solid CO₂) to CO₂ gas).

In this case, the equation shows gas to solid, which is deposition. Note that the reverse process (solid to gas) is sublimation, but here the arrow points from gas to solid.

Answer: B. deposition

*These A.I. responses have been individually checked to ensure they match the accepted answer, but explanations may still be incorrect. Responses may give guidance but the A.I. might not be able to answer the question! This is particularly the case for questions based on diagrams, which the A.I. typically cannot interpret.
Grade Gorilla uses Gemini, Deepseek and a range of other A.I. chatbots to generate the saved responses. Some answers have had human intervention for clarity or where the A.I. has not been able to answer the question.

Question 8:

When steam condenses to water, it is a phase change from gas to liquid. Let's evaluate each statement:

I. The kinetic energy of the particles increases:
This is false. During condensation, the particles are losing energy as they transition from gas to liquid. The kinetic energy (related to motion) decreases because the particles slow down.

II. The distance between the particles increases:
This is false. In a gas, particles are far apart; in a liquid, they are closer together. So, the distance between particles decreases during condensation.

III. The temperature remains constant:
This is true. During a phase change (like condensation), the temperature remains constant because the energy being removed is used to overcome intermolecular forces rather than to change the kinetic energy of the particles.

Therefore, only III is correct.

Answer: D. III only

*These A.I. responses have been individually checked to ensure they match the accepted answer, but explanations may still be incorrect. Responses may give guidance but the A.I. might not be able to answer the question! This is particularly the case for questions based on diagrams, which the A.I. typically cannot interpret.
Grade Gorilla uses Gemini, Deepseek and a range of other A.I. chatbots to generate the saved responses. Some answers have had human intervention for clarity or where the A.I. has not been able to answer the question.

Question 9:

The graph in option A correctly represents the cooling curve of a pure substance. This is because a pure substance has a single, distinct melting and freezing point.

Here's a breakdown of the cooling process represented in the graph:

The substance starts as a liquid at 75°C and cools down, which is shown by the downward-sloping line.

When the substance reaches its freezing point of 50°C, it begins to change from a liquid to a solid. During this phase change, energy is released as latent heat of fusion, which keeps the temperature constant until all of the substance has solidified. This is represented by the flat, horizontal section of the graph at 50°C.

Once the substance is completely solid, it continues to cool down to room temperature, which is shown by the final downward-sloping line.

The graph in option B is incorrect because it shows a continuous decrease in temperature. This is characteristic of a mixture or an impure substance, which does not have a fixed freezing point.

*These A.I. responses have been individually checked to ensure they match the accepted answer, but explanations may still be incorrect. Responses may give guidance but the A.I. might not be able to answer the question! This is particularly the case for questions based on diagrams, which the A.I. typically cannot interpret.
Grade Gorilla uses Gemini, Deepseek and a range of other A.I. chatbots to generate the saved responses. Some answers have had human intervention for clarity or where the A.I. has not been able to answer the question.

Question 10:

To determine which change of state is endothermic, recall that endothermic processes absorb energy (heat) from the surroundings. Phase changes that require energy input are endothermic.

Let's analyze each option:

A. H₂O(g) → H₂O(l)
This is condensation (gas to liquid). Condensation releases energy (exothermic).

B. I₂(s) → I₂(g)
This is sublimation (solid to gas). Sublimation requires energy to break intermolecular forces and is endothermic.

C. Na(l) → Na(s)
This is freezing (liquid to solid). Freezing releases energy (exothermic).

D. 2C₆H₆(l) + 15O₂(g) → 12CO₂(g) + 6H₂O(l)
This is a combustion reaction (burning of benzene). Combustion reactions are exothermic (they release heat).

Therefore, only option B (I₂(s) → I₂(g)) is endothermic.

*These A.I. responses have been individually checked to ensure they match the accepted answer, but explanations may still be incorrect. Responses may give guidance but the A.I. might not be able to answer the question! This is particularly the case for questions based on diagrams, which the A.I. typically cannot interpret.
Grade Gorilla uses Gemini, Deepseek and a range of other A.I. chatbots to generate the saved responses. Some answers have had human intervention for clarity or where the A.I. has not been able to answer the question.