5th Grade Science Quiz Chapter 5 - Elements And Compounds

Explanation
Sand floating in water is an example of a mixture. A mixture is formed when two or more substances are combined physically and retain their individual properties. In this case, sand and water are mixed together, but they do not chemically react or combine to form a new substance. The sand particles remain separate and are suspended in the water, creating a heterogeneous mixture.

Explanation
Burning wood is a chemical change because it involves a chemical reaction. When wood is burned, it undergoes a combustion reaction where it reacts with oxygen in the air to produce carbon dioxide, water vapor, and heat. This chemical reaction results in the formation of new substances with different properties than the original wood. Therefore, burning wood is considered a chemical change rather than a physical change or a mixture.

Explanation
When squeezing a lemon, the physical properties of the lemon, such as its shape, size, and volume, change. However, the chemical composition of the lemon remains the same. The squeezing action only alters the physical state of the lemon, causing its juice to be released. Therefore, squeezing a lemon is considered a physical change rather than a chemical change or a mixture.

Explanation
Iodine dissolved in alcohol is a mixture because it is a combination of two substances that can be separated by physical means. In this case, iodine and alcohol are not chemically reacting with each other, but rather the iodine particles are dispersed throughout the alcohol. This can be demonstrated by evaporating the alcohol, which would leave behind the iodine. Therefore, the iodine dissolved in alcohol is an example of a mixture.

Explanation
Breaking an egg is a physical change because it does not involve a change in the chemical composition of the egg. The egg remains the same substance, but its physical state is altered. Breaking the egg only results in the physical separation of its shell and contents, without any new substances being formed.

Explanation
When silver tarnishes, it undergoes a chemical change. This is because the silver reacts with substances in the air, such as sulfur or hydrogen sulfide, forming a new compound called silver sulfide. This reaction changes the chemical composition of the silver, resulting in a darkening or discoloration of the surface. Unlike a physical change, where the substance retains its original properties, tarnishing involves a chemical reaction that alters the silver's composition and properties. Therefore, tarnishing silver is considered a chemical change.

Explanation
Atoms are the fundamental building blocks of matter. They are the smallest units of a chemical element that retain the chemical properties of that element. Atoms consist of protons, neutrons, and electrons. Protons have a positive charge, neutrons have no charge, and electrons have a negative charge. These tiny moving parts combine in different ways to form molecules and compounds, giving rise to the vast diversity of matter in the universe.

Explanation
The correct answer is "None of the above" because particles moving rapidly around the nucleus are called electrons. Neutrons and protons are not particles that move rapidly around the nucleus, rather they are found within the nucleus of an atom.

Explanation
The question is asking about the different states of matter based on the movement of its molecules. The correct answer is solid, liquid, gas. In a solid, the molecules are tightly packed and vibrate in fixed positions. In a liquid, the molecules are close together but can move past each other. In a gas, the molecules are far apart and move freely.