Unit 4: Properties of Matter Post Test

Andy has two samples of liquids. Sample A has a pH of 4, and sample B has a pH of 6. What can Andy conclude about these two samples? Sample A is ___ and sample B is ___.

• Sample A is acidic and sample B is neutral.

• Sample A is neutral and sample B is acidic.

• Sample A is alkali and sample B is acidic.

• Sample A is neutral and sample B is alkali.

• Sample A is acidic and sample B is alkali.

Answer explanation

Sample A has a pH of 4, which is below 7, indicating it is acidic. Sample B has a pH of 6, which is still below 7 but closer to neutral, making it slightly acidic. Therefore, Sample A is acidic and Sample B is neutral.

Martina has a sample of an unknown substance. She measures the substance. Its mass is 13.5 grams, and its volume is 5 cm³. Which metal might her sample be made of?

• Silver

• Copper

• Iron

• Aluminum

Answer explanation

To find the density, divide mass by volume: 13.5 g / 5 cm³ = 2.7 g/cm³. The density of copper is approximately 8.96 g/cm³, which is closest to the calculated density, indicating the sample is likely copper.

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NGSS.MS-PS1-2

Salt is dissolved in a flask of tap water. Distilling the mixture causes the salt to separate from the water. Which type of energy is required to begin the distilling process?

• A. chemical energy

• B. electrical energy

• C. mechanical energy (motion)

• D. thermal energy

Answer explanation

Thermal energy is required to heat the water, causing it to evaporate. As the water vapor cools, it condenses back into liquid, leaving the salt behind. Thus, thermal energy is essential for the distilling process.

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NGSS.MS-PS1-4

Dalton’s completing an investigation in the science lab. He observes that a sample of liquid turns to gas at 135°C. What’s this temperature called?

• boiling point

• freezing point

• melting point

• room temperature

• standard temperature

Answer explanation

The temperature at which a liquid turns to gas is called the boiling point. Since Dalton observed the liquid turning to gas at 135°C, this indicates that 135°C is the boiling point of that liquid.

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NGSS.MS-PS1-4

Which property of a substance can be determined using a pH indicator?

• acidity

• boiling point

• density

• electrical conductivity

• thermal conductivity

Answer explanation

A pH indicator is specifically designed to measure the acidity of a substance by changing color in response to different pH levels. Therefore, the correct property that can be determined using a pH indicator is acidity.

A chemist is trying to identify a sample of metal that is listed in this table. She passes an electrical current through the sample and finds that, of the metals listed in the table, it's one of the best conductors. Then she heats the metal to 1000°C, which is the highest temperature her heater allows. The metal doesn’t melt. Which type of metal does the chemist have?

• aluminum

• copper

• zinc

• silver

• nickel

Answer explanation

The chemist identifies copper as the best conductor among the options. Copper has a high melting point (1085°C), so it remains solid at 1000°C, confirming it as the metal in the sample.

Tags

NGSS.MS-PS1-2

What kind of matter is smoke?

• solution

• suspension

• colloid

• compound

• molecule

Answer explanation

Smoke is a colloid because it consists of tiny solid particles dispersed in a gas (air). Unlike solutions, the particles in a colloid do not settle out, which is characteristic of smoke.

An apple pudding is prepared by combining apples, sugar, butter, and lemon juice. To which category does it belong?

• compound

• mixture

• element

• molecule

• atom

Answer explanation

An apple pudding is made by combining various ingredients like apples, sugar, butter, and lemon juice without forming a new chemical substance. Therefore, it is classified as a mixture, as the components retain their individual properties.

Consider a mixture of soil and water and compare it to a colloid, such as milk. Which property best differentiates these two mixtures?

• Soil and water is a suspension because it consists of minute particles suspended in the medium. Milk is a colloid because it consists of larger particles suspended in the medium, which start to settle when allowed to stand.

• Soil and water is a colloid because it consists of minute particles suspended in the medium. Milk is a suspension because it consists of larger particles suspended in the medium, which start to settle when allowed to stand.

• Soil and water is a colloid because it has a uniform composition. Milk is a suspension because it doesn’t have a uniform composition.

• Soil and water is a suspension because it consists of larger particles suspended in the medium, which start to settle when allowed to stand. Milk is a colloid because it consists of minute particles that remain suspended in the medium.

• Soil and water is a suspension because it has a uniform composition. Milk is a colloid because it doesn’t have a uniform composition.

Answer explanation

Soil and water is a suspension due to larger particles that settle over time, while milk is a colloid with minute particles that remain suspended, differentiating their stability and composition.

Emma is doing a laboratory experiment to separate components of crude oil. She decides to use a technique that will separate the components based on their boiling points. Which technique uses this principle?

• filtration

• distillation

• centrifugation

• chromatography

• titration

Answer explanation

Distillation is the technique that separates components based on their boiling points, making it the correct choice for Emma's experiment with crude oil.

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NGSS.MS-PS1-4