Isaz Chemistry A Block 3 Pre-test

Accuracy refers to how close a measurement is to the true value of the quantity being measured. It is a measure of how well the measurement represents the actual value. In other words, accuracy indicates the degree of correctness or precision in a measurement. It is important to have accurate measurements in scientific experiments and other fields to ensure reliability and validity of the results.

A hypothesis is a possible explanation for an observation that can be tested through scientific investigations. It is a proposed explanation or prediction based on existing knowledge or observations. By conducting experiments or gathering data, scientists can test the validity of a hypothesis and determine if it is supported or refuted. Hypotheses are an essential component of the scientific method and are used to guide research and further our understanding of the natural world.

An element is not a fundamental particle in an atom. An element is a substance that is made up of only one type of atom. Atoms are composed of three fundamental particles: electrons, protons, and neutrons. Electrons have a negative charge and orbit around the nucleus of an atom. Protons have a positive charge and are found in the nucleus. Neutrons have no charge and are also found in the nucleus. Therefore, the correct answer is element, as it is not a fundamental particle but rather a substance composed of atoms.

When matter moves from a gas to a liquid, it is called condensation. This process occurs when the gas molecules lose energy and come together to form liquid droplets. This can happen when the temperature of the gas decreases or when the pressure increases. Condensation is a common phenomenon that can be observed in everyday life, such as when water vapor in the air turns into dew on a cold surface or when steam from a hot shower condenses on a mirror.

Sodium is a correct answer because it is a chemical element. Elements are substances that cannot be broken down into simpler substances by chemical means. Sodium is a highly reactive metal that belongs to the alkali metal group and has the atomic number 11. It is commonly found in compounds such as sodium chloride (table salt) but in its pure form, it exists as an element.

A chemical compound is formed when two or more chemical elements combine together. It is not a subatomic particle or a combination of protons and electrons. It is also different from a mixture, which is a combination of two or more substances. Therefore, the correct answer is that a chemical compound is a combination of two or more chemical elements.

A change in a substance that involves a change in the identity of the substance is referred to as a chemical change. In a chemical change, the atoms rearrange themselves to form new substances with different properties. This is different from a physical change, where the substance may change its form or state but its identity remains the same. Examples of chemical changes include combustion, oxidation, and decomposition reactions.

The negatively-charged particle in an atom is the electron. Electrons are located outside the nucleus and have a negative charge. They are much smaller and lighter than protons and neutrons, and they are responsible for the majority of chemical reactions and electrical conductivity in materials.

An atom of oxygen contains eight electrons, which matches the information given in the question. Therefore, the correct answer is oxygen.

An ionic bond forms when one or more pairs of electrons are transferred from one atom to another, not shared. This results in the formation of positively charged ions (cations) and negatively charged ions (anions), which are then attracted to each other due to their opposite charges, forming an ionic bond. Therefore, the statement that an ionic bond forms when one or more pairs of electrons are shared between two atoms is incorrect.