Matter and Energy Test

Which statement best describes evidence that a chemical reaction occurs as a cake bakes?

• The water in the cake batter evaporates

• The cake rises as gas bubbles form in the baking cake

• The cake takes the shape of the container in which it is baked

• The water in cake batter is used to keep the cake moist as it bakes

Answer explanation

The best evidence that a chemical reaction occurs as a cake bakes is the cake rising due to gas bubbles forming in it. As the cake bakes, the heat causes chemical reactions between ingredients, producing carbon dioxide gas, which forms bubbles and causes the cake to rise. This is a clear indication of a chemical reaction taking place.

Water and oil are poured into the same container. An object is added. The materials are allowed to sit and their final positions are shown in the illustration.

• The object has the lowest density

• Water is more dense than oil.

• The object is more dense than water

• Oil has the highest density

Answer explanation

In the given question, water and oil are poured into the same container along with an object. As the materials settle, it indicates that water is more dense than oil, because water settles at the bottom. The object, which is denser than the water, sinks into the water layer, proving that the object is more dense than water.

Which of the following properties of an unknown substance would allow it to be classified as a mixture? The unknown substance-

• Has an overall density greater than that of water

• Is able to easily conduct an electric current

• Can somewhat be shaped into sheets

• You can distinguish the different parts that make up the substance

Answer explanation

A mixture is a combination of two or more substances in which each substance retains its individual properties. The option 'You can distinguish the different parts that make up the substance' indicates that the substance is not uniform and has distinguishable components, which is a characteristic of mixtures.

Which of the following statements best describes gases? Gases-

• Cannot easily change their volume by compression

• Maintain a constant shape, regardless of the container

• Can change shape and volume depending on the container

• Have a fixed size and shape, regardless of the container

Answer explanation

Gases can change shape and volume depending on the container they are in. Unlike solids and liquids, gases do not maintain a constant shape or size. Instead, they take the shape and fill the volume of the container they occupy, making it the correct choice.

Which type of substances have a definite shape and fixed volume?

• Solids only

• Liquids and solids

• Gases only

• Liquids and gases

Answer explanation

Solids have a definite shape and fixed volume because their particles are closely packed together and are arranged in a fixed pattern. This structure results in solids maintaining their shape and volume, unlike liquids and gases, whose particles have more freedom to move and can change their shape and volume.

Which of the following properties of an unknown substance would allow it to be classified as a pure substance?

• Is not able to conduct any electric current

• Has an overall density greater than that of water

• Consists of a solid dissolved in distilled water

• Is composed throughout of one and only one element

Answer explanation

A pure substance is defined as a material with a consistent composition of one type of element or compound. The option 'Is composed throughout of one and only one element' directly fits this definition, as it states that the substance consists solely of a single element, making it a pure substance.

Which of the following can be concluded based on the results?

• Sphere 1 is more dense than sphere 2

• Sphere 2 is less dense than sphere 3

• Sphere 3 is less dense than sphere 2

• Sphere 2 is less dense than sphere 1

Answer explanation

The question was about identifying the correct comparison of density between different spheres. The correct answer is that Sphere 3 is less dense than Sphere 2. This means that Sphere 2 has more mass per unit of volume than Sphere 3, making it denser.

A sliver ring reacts with compounds containing sulfur in the air to form silver sulfide, a black substance that makes up the tarnish on the surface of silver objects. To remove the tarnish from the ring, students placed it in a pan lined with aluminum foil and added hot water. Baking soda was added to the hot water and stirred. Students made observations about the process. 

Which observation of the process provides evidence of chemical reaction?

• Hot water heated the aluminum foil

• The liquid solution changed color

• The pan was lined with aluminum foil

• The hot water cooled

Answer explanation

The correct answer is 'The liquid solution changed color'. This observation indicates evidence of a chemical reaction because when a substance changes its color, it normally indicates that a new substance has been formed. In this case, the interaction between the silver ring, sulfur compounds, baking soda, and hot water may have caused a chemical reaction leading to a color change in the solution.

Which of the following properties of an unknown substance would allow it to be classified as a pure substance?

• Can be dissolved into a solution

• Has a definite composition throughout

• Combines easily with other substances

• Is made of a single element or compound

Answer explanation

A pure substance is composed of only one type of particle - either an element or a compound. The property of being made of a single element or compound signifies a pure substance. Other properties like dissolution or combining with other substances are not definitive traits of a pure substance.

A student is trying to classify an unidentified, solid gray material as a metal or a nonmetal.

Which of the following questions will best help the student classify the material?

• Is the material malleable or ductile?

• Does the material feel hard to the touch?

• Will the material float in water?

• Does the material feel rough or smooth?

Answer explanation

The best question for classifying the material as metal or nonmetal is whether it is malleable or ductile. Metals tend to be malleable and ductile, while nonmetals do not have these properties. The other questions are not relevant to the material's classification.