Chapter 6 - Chapter Test (10 Questions)

Normal rainfall is slightly acidic due to the presence of carbon dioxide in the atmosphere, which forms carbonic acid when it reacts with water. This lowers the pH of the rainwater. A pH between 5 and 7 indicates a slightly acidic nature, as it is below the neutral pH of 7.

Digestion is an example of a chemical change because it involves the breaking down of food molecules into simpler substances through chemical reactions. In the process of digestion, enzymes and acids in the stomach and intestines break down complex carbohydrates, proteins, and fats into smaller molecules that can be absorbed by the body. This chemical transformation is different from physical changes like grating cheese, ripping paper, or sawing wood, which do not involve the alteration of the chemical composition of the substances involved.

Bases form hydroxide ions (OH-) in water. When a base is dissolved in water, it releases hydroxide ions, which are negatively charged. These hydroxide ions then combine with hydrogen ions (H+) from water to form water molecules (H2O). This process is known as the ionization of bases and is responsible for the characteristic properties of bases, such as their ability to neutralize acids and their bitter taste.

Weak tea is an example of a dilute solution because it is made by adding a small amount of tea leaves to a large amount of water. The tea leaves are not concentrated in the solution, resulting in a low concentration of solute (tea) compared to the solvent (water).

A solution with a pH of 9 is considered basic. The pH scale ranges from 0 to 14, with 7 being neutral. Solutions with a pH less than 7 are acidic, while solutions with a pH greater than 7 are basic. Therefore, a solution with a pH of 9 falls on the basic end of the pH scale.

In this question, we are given that 40 mL of alcohol forms a solution with 30 mL of water. The solvent in a solution is the component that is present in the larger amount. Since alcohol is present in a larger quantity (40 mL) compared to water (30 mL), alcohol is the solvent in this solution.

A scientist can determine whether a water solution contains salt or sugar by testing the electrical conductivity of the solution. This is because salt, which is an electrolyte, will dissociate into ions in water and allow the flow of electric current. On the other hand, sugar, which is a non-electrolyte, will not dissociate into ions and will not conduct electricity. Therefore, by measuring the electrical conductivity of the solution, the scientist can determine whether it contains salt or sugar.

Neutralization is the correct answer because when an acid and a base react, they undergo a chemical reaction known as neutralization. During this reaction, the acid donates hydrogen ions (H+) to the base, which accepts them and forms water and a salt. The resulting solution is neither acidic nor basic, hence the term neutralization. This process is commonly used to neutralize the effects of acids and bases, and it is an important concept in chemistry.

An indicator is used in science to find the pH of a solution, which tells us the potential of hydrogen in it. The pH scale measures the acidity or alkalinity of a solution, with a pH of 7 being neutral, values below 7 indicating acidity, and values above 7 indicating alkalinity. Indicators are substances that change color depending on the pH of the solution they are added to, allowing scientists to visually determine the pH level. By using indicators, scientists can quickly and easily determine the acidity or alkalinity of a solution for various scientific experiments and applications.

A suspension is a liquid mixture in which particles can be seen and easily separated by filtration. In a suspension, the particles are usually larger and do not dissolve in the liquid, causing them to settle at the bottom over time. This makes it possible to separate the particles from the liquid by passing it through a filter.

The characteristic property of acids is that they turn blue litmus paper red. This is a common test used to identify the presence of an acid. When an acid comes into contact with blue litmus paper, the paper changes color from blue to red, indicating the acidic nature of the substance. This is due to the release of hydrogen ions (H+) from the acid, which react with the litmus paper and cause the color change.

When a compound dissolves in water, each of its particles is surrounded by water molecules. This is because water is a polar molecule, meaning it has a slightly positive charge on one end and a slightly negative charge on the other end. The positive end of the water molecule is attracted to the negatively charged ions in the compound, while the negative end of the water molecule is attracted to the positively charged ions. This attraction causes the water molecules to surround and separate the particles of the compound, effectively dissolving it.