1.
Is Mercury an element, compound, or mixture?
Correct Answer
A. Element
Explanation
Mercury is an element because it is a pure substance that cannot be broken down into simpler substances by chemical means. It is found on the periodic table with the symbol Hg and atomic number 80. Elements are the building blocks of matter and consist of only one type of atom. In the case of mercury, it is composed solely of mercury atoms.
2.
Is table salt, sodium chloride, an element, a compound or a mixture?
Correct Answer
B. Compound
Explanation
Table salt, sodium chloride, is a compound. A compound is a substance made up of two or more elements that are chemically bonded together. In the case of table salt, it is composed of sodium and chlorine atoms, which are held together by ionic bonds. This means that the atoms are not physically mixed together, but rather chemically combined to form a new substance with different properties than its individual components. Therefore, table salt is classified as a compound.
3.
Is pure water an element, compound or a mixture?
Correct Answer
B. Compound
Explanation
Pure water is a compound. A compound is a substance made up of two or more different elements chemically combined in a fixed ratio. Water is composed of two hydrogen atoms and one oxygen atom, chemically bonded together to form a molecule of water. Therefore, since water is composed of different elements (hydrogen and oxygen) combined in a fixed ratio, it is classified as a compound.
4.
What type of a mixture is Coffee?
Correct Answer
A. A homogeneous mixture
Explanation
Coffee is considered a homogeneous mixture because it is composed of multiple substances that are evenly distributed throughout the mixture. When coffee is brewed, the water extracts various compounds such as caffeine, oils, and flavors from the coffee beans. These substances mix uniformly with the water, resulting in a consistent composition and appearance throughout the entire solution. Therefore, coffee can be classified as a homogeneous mixture.
5.
What type of mixture is the ocean?
Correct Answer
A. Heterogeneous mixture
Explanation
The ocean is a heterogeneous mixture because it is composed of various substances that are not evenly distributed throughout. It contains a combination of salt, minerals, gases, and organic matter, all of which are dispersed unevenly in the water. Additionally, the ocean exhibits different properties and characteristics in different regions, such as temperature, salinity, and density, further supporting the classification of it being a heterogeneous mixture.
6.
Tap water (including everything in it) is...
Correct Answer
B. A mixture
Explanation
Tap water is considered a mixture because it is composed of various substances, such as dissolved minerals, gases, and impurities. These components are not chemically bonded together but rather exist in a heterogeneous mixture. Additionally, tap water can vary in composition depending on the source and treatment process, further supporting the classification as a mixture.
7.
Gold is a
Correct Answer
A. Element
Explanation
Gold is a chemical element with the symbol Au and atomic number 79. It is a dense, soft, yellow, and highly malleable metal. Gold is a pure substance and cannot be broken down into simpler substances by chemical means. Therefore, it is classified as an element.
8.
Carbon Dioxide is a
Correct Answer
B. Compound
Explanation
Carbon dioxide is a compound because it is made up of two different elements, carbon and oxygen, chemically bonded together. In a compound, the elements are combined in a fixed ratio and can only be separated by a chemical reaction. Carbon dioxide is formed when carbon atoms combine with oxygen atoms through a chemical reaction, resulting in a stable compound with specific properties.
9.
Vegetable Soup is a
Correct Answer
C. Heterogeneous mixture
Explanation
A vegetable soup is considered a heterogeneous mixture because it is made up of different components that are visibly distinguishable from each other. In a vegetable soup, there are various ingredients such as vegetables, spices, and broth, which can be seen as separate particles within the mixture. This is in contrast to a homogeneous mixture where the components are uniformly distributed and cannot be easily differentiated.
10.
Iron is a
Correct Answer
A. Element
Explanation
Iron is classified as an element because it is a pure substance that cannot be broken down into simpler substances by chemical means. It is composed of only one type of atom, specifically iron atoms. Elements are the building blocks of all matter and are represented on the periodic table. In contrast, compounds are made up of two or more different elements chemically combined, while mixtures are a combination of two or more substances that are not chemically bonded together. Therefore, iron being an element is the correct answer.
11.
Water can boil at 100 degrees celsius. What type of change is this?
Correct Answer
B. A pHysical change
Explanation
Boiling water at 100 degrees Celsius is a physical change because it involves a change in the state of matter from liquid to gas, without any alteration in the chemical composition of water. The water molecules gain enough energy to overcome the intermolecular forces holding them together, resulting in the formation of water vapor. This change is reversible, as the water vapor can condense back into liquid water when cooled.
12.
Water can be separated into hydrogen and oxygen by electrolyisis.
Correct Answer
B. This is a chemical change
Explanation
When water undergoes electrolysis, it is chemically decomposed into its constituent elements, hydrogen and oxygen. This process involves the breaking of the chemical bonds within the water molecules and the formation of new bonds between hydrogen and oxygen atoms. Therefore, the separation of water into hydrogen and oxygen by electrolysis is a chemical change.
13.
When sugar dissolves into water...
Correct Answer
B. This is a pHysical change
Explanation
When sugar dissolves into water, it undergoes a physical change. This is because the sugar molecules are dispersed throughout the water, forming a homogeneous mixture. No new substances are formed, and the chemical composition of both sugar and water remains the same. The process of dissolving is purely a physical interaction between the sugar molecules and the water molecules, resulting in the formation of a solution.
14.
Vinegar reacts with baking soda to create a brand new gas (Carbon Dioxide)
Correct Answer
A. This is a chemical change
Explanation
When vinegar (acetic acid) reacts with baking soda (sodium bicarbonate), it undergoes a chemical reaction, resulting in the formation of a new gas, carbon dioxide. This reaction involves the breaking and forming of chemical bonds between the molecules of vinegar and baking soda, leading to the creation of completely new substances. Therefore, the given statement is correct, and this process represents a chemical change rather than a physical change.
15.
Gasoline burns in the presence of oxygen.
Correct Answer
A. This is a chemical change
Explanation
When gasoline burns in the presence of oxygen, it undergoes a chemical reaction called combustion. During combustion, the molecules of gasoline react with oxygen to produce carbon dioxide, water vapor, and release energy in the form of heat and light. This change is considered a chemical change because the chemical composition of the gasoline molecules is altered, resulting in the formation of new substances with different properties.
16.
Iron rusts, producing a layer of oxide on the outside of the metal.
Correct Answer
B. This is a chemical change
Explanation
When iron rusts, it undergoes a chemical reaction with oxygen in the presence of moisture, resulting in the formation of iron oxide. This process involves a rearrangement of atoms and the formation of new chemical bonds. Therefore, the transformation of iron into iron oxide is considered a chemical change rather than a physical change, which only involves a change in physical properties such as shape or state.
17.
Burning wood is an example of a
Correct Answer
A. Chemical change
Explanation
Burning wood is an example of a chemical change because it involves a chemical reaction. When wood is burned, it undergoes a process called combustion, where it reacts with oxygen in the air to produce heat, light, and various gases such as carbon dioxide and water vapor. This change is irreversible, as the wood is transformed into different substances with different properties. Therefore, burning wood is not a physical change, as it does not involve a change in the state or form of the wood, but rather a chemical transformation.
18.
Nitrogen is an example of a
Correct Answer
A. Element
Explanation
Nitrogen is an example of an element because it is a pure substance that cannot be broken down into simpler substances. It consists of only one type of atom, which is nitrogen. Elements are the fundamental building blocks of matter and cannot be further divided by chemical means.
19.
Raisin oatmeal is a
Correct Answer
A. Heterogeneous mixture
Explanation
A heterogeneous mixture is a combination of different substances that are visibly distinguishable from one another. In the case of raisin oatmeal, it is made up of various components such as oats, raisins, and possibly other ingredients like sugar or spices. These components can be easily identified and separated from each other. Therefore, raisin oatmeal is considered a heterogeneous mixture.
20.
Calcium Chloride is a...
Correct Answer
C. Compound
Explanation
Calcium chloride is a compound because it is formed by the chemical bonding of calcium and chloride ions. It has a fixed composition and a specific chemical formula (CaCl2). Compounds are pure substances that can be broken down into simpler substances through chemical reactions. In the case of calcium chloride, it can be dissociated into calcium and chloride ions when dissolved in water. Therefore, it is classified as a compound rather than an element, homogeneous mixture, or heterogeneous mixture.