Sras Gr.7 Science (Elements)

When an acid is dissolved in water, it releases hydrogen ions (H+) into the solution. These hydrogen ions combine with water molecules to form hydronium ions (H3O+). On the other hand, hydroxide ions (OH-) are present in water. However, the concentration of hydrogen ions is higher than the concentration of hydroxide ions in an acidic solution. Therefore, there are indeed more hydrogen ions than hydroxide ions in the solution, making the statement true.

Gravel doesn't belong to the group because it is not a type of liquid or beverage like the other options. Salt water, juice, Gatorade drinks, and soda drinks are all liquids that can be consumed, while gravel is a solid material used for construction purposes.

The pH scale is a measure of the acidity or alkalinity of a substance. It ranges from 0 to 14, with 7 being considered neutral. A pH level of 7 indicates that the substance is neither acidic nor alkaline, making it neutral. Therefore, the statement that the pH level of neutral substances is 7 is correct.

When a pure substance has a chemical formula, it is considered a compound. A compound is a substance made up of two or more different elements that are chemically bonded together in a fixed ratio. The chemical formula of a compound represents the types and number of atoms present in the compound. Therefore, if a pure substance has a chemical formula, it indicates that it is a compound.

Most bases have hydroxide in their chemical composition because hydroxide ions (OH-) are responsible for the basic properties of a substance. Bases are substances that can accept protons (H+) or donate pairs of electrons. When a base dissolves in water, it forms hydroxide ions, which can react with acids to form water and a salt. Examples of bases include sodium hydroxide (NaOH) and calcium hydroxide (Ca(OH)2). Therefore, it is true that most bases have hydroxide in their chemical composition.

Mixtures are not considered as pure substances because they are made up of two or more different types of substances that are physically combined. In a mixture, the components can be separated by physical means such as filtration or evaporation. In contrast, pure substances are made up of only one type of substance and cannot be separated into other substances by physical means. Therefore, the statement that mixtures are considered as pure substances is false.

Compound and elements are considered pure substances because they are made up of only one type of atom or molecule. Compounds are formed when two or more elements chemically combine, while elements are substances that cannot be broken down into simpler substances by chemical means. Both compounds and elements have definite chemical compositions and distinct properties, making them pure substances.

Acids do not feel slippery when touched. In fact, they usually feel sticky or corrosive. This is because acids have the ability to react with and corrode certain materials, including human skin. Therefore, the statement that most acid feels slippery when touched is false.

Metals react with acids, not bases. Bases, on the other hand, can react with acids to form salts and water. This reaction is known as neutralization. Therefore, the statement that bases react violently with metals is incorrect.

Copper wire belongs to the group "element" because copper is a chemical element with the atomic number 29. It is a pure substance made up of only copper atoms and cannot be broken down into simpler substances by chemical means. Therefore, copper wire is considered an element.

Compounds are represented by their chemical formula, which is a symbolic representation of the elements present in the compound and their respective ratios. The chemical formula provides information about the types and number of atoms in a compound, allowing scientists to identify and study different compounds.

The given statement is false. The pH scale ranges from 0 to 14, with 0 being the most acidic and 14 being the most alkaline. Therefore, the higher the pH level of a substance, the less acidic it is.

Milk is the only item in the list that is not a mixture of different substances. Cereal in milk, pulpy orange juice, fruit salad, and Halo-Halo are all examples of heterogeneous mixtures because they contain different components that can be easily distinguished. Sand is also a heterogeneous mixture as it is made up of different particles. However, milk is a homogeneous mixture because it is made up of a single phase and its components are evenly distributed throughout.

Elements are the simplest chemical substances because they consist of only one type of atom. Each element has its own unique set of atoms, which are all identical to one another. These atoms cannot be broken down into simpler substances by chemical means. Therefore, elements are the fundamental building blocks of matter and form the basis of the periodic table.

The correct answer choices are all examples of heterogeneous mixtures. Heterogeneous mixtures are mixtures in which the components are not evenly distributed and can be visibly distinguished. Peanut butter is a mixture of peanut particles and oil. Concrete is a mixture of cement, sand, gravel, and water. Carbonated beverages or beer contain gas bubbles dispersed in liquid. Oil and water do not mix and form separate layers in a mixture.

The compounds in the given list are Acetic Acid, Water, Carbon dioxide, Methane, Sucrose, Cooking oil. These substances are compounds because they are made up of two or more elements chemically bonded together. Acetic acid is a compound composed of carbon, hydrogen, and oxygen. Water is a compound made up of hydrogen and oxygen. Carbon dioxide is composed of carbon and oxygen. Methane is composed of carbon and hydrogen. Sucrose is a compound made up of carbon, hydrogen, and oxygen. Cooking oil is a mixture of different compounds, but it contains compounds such as fatty acids and glycerol.