Module 1.1 Properties of Matter

Which technique would most easily be used to separate a mixture of partly crushed rock particles and sand?

• Filtration

• Separating funnel

• Sieving

• Sedimentation and decanting

Answer explanation

The correct technique to separate a mixture of partly crushed rock particles and sand is Sieving. Sieving works by allowing smaller sand particles to pass through the holes of a sieve while retaining the larger rock particles. Filtration is incorrect because it is more suited for separating solids from liquids, not for different sizes of solid particles. Separating funnel is used to separate immiscible liquids, making it inappropriate for this solid-solid mixture. Sedimentation and decanting are more effective for separating solids from liquids, so they wouldn't work well here either.

The table shows information about the properties of four elements.

Based on this information which of the following statements is correct?

• Gold conducts heat five times better than potassium.

• A sample of potassium metal is less dense than water.

• Mercury is an excellent electrical conductor compared to the other metals.

• Bromine is a gas at room temperature.

Answer explanation

Gold's conductivity is 45, while potassium's is 14, so dividing 45 by 14 gives about 3.2, not 5, meaning gold does not conduct heat five times better than potassium. Potassium has a density of 0.86 g/mL, which is less than water’s density of 1 g/mL, so it would float on water, making this statement correct. Mercury has a conductivity of 1, lower than both gold's 45 and potassium's 14, so it is not a better conductor than these metals, making the statement incorrect. Bromine has a boiling point of 59°C, which is above room temperature, so it would be a liquid at room temperature, not a gas, thus making this statement incorrect.

Which of the following is a heterogeneous mixture?

• A salt solution

• A salt-pepper mixture

• Pure air

• Natural gas

Answer explanation

The correct answer is a salt-pepper mixture. A heterogeneous mixture is one in which the different components can be visibly distinguished and are not uniformly distributed. In a salt-pepper mixture, you can see and separate the individual grains of salt and pepper. A salt solution is homogeneous because the salt dissolves completely, creating a uniform mixture. Pure air and natural gas are also homogeneous mixtures because their components are evenly distributed at a molecular level.

When analysed, a compound was found to have 50.0% sulfur and 50.0% oxygen by mass.

Which of the following is the correct chemical formula for this compound?

• SO

• SO₂

• SO₃

• S₂O

Answer explanation

The correct chemical formula for the compound with 50.0% sulfur and 50.0% oxygen by mass is SO. To determine this, consider the molar masses: sulfur has a molar mass of approximately 32 g/mol and oxygen about 16 g/mol. If the compound is 50% sulfur and 50% oxygen by mass, the ratio of sulfur to oxygen atoms is 1:1, giving the formula SO.

SO2 and SO3 are incorrect because they represent compounds with more oxygen atoms relative to sulfur. S2O is not a common compound and does not fit the given percentage composition.

Which of the following represents a homogeneous mixture of two elements?

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