Chemistry (Quiz Teórico)

• A solution with a pH of 7 is neutral (neither acidic nor basic).
• Acidic solutions have a pH less than 7, while basic solutions have a pH greater than 7.
• Chemistry is the study of matter, its properties, structure and changes and how it interacts with energy.
• Matter is anything that has mass and volume.
• Auxiliary sciences are sciences that helps Chemistry to obtain the knowledge
• The scientific method is a series of steps followed by scientific investigators to answer specific questions  about the world.
• Observation - The first step involves observing something about the natural world or some phenomenon.
• Question/Hypothesis - After making observations, scientists ask questions about what they have observed.
• Experiment – Scientists conduct experiments to test their predictions.
• Analysis of results - Data is analyzed to determine if it supports the hypothesis.
• Conclusion - Based on analysis of the results, conclusions can be drawn.
• Communication - Results must be communicated through publication so other scientists may review them.
• The two classifications of matter are pure substances and mixtures
• Mixture - Two or more different kinds of atoms or molecules combined together
• Pure Substance - A single type of atom or molecule (e.g., gold, oxygen gas)
• Compound - Pure substance made up of two or more elements chemically bonded together
• Element - Pure substance that cannot be broken down into simpler substances by chemical means
• Homogeneous Mixture - Uniform mixture with particles evenly distributed throughout
• Heterogenous Mixture - Non-uniform mixture where particles do not mix well (e.g., sand mixed with water)
• Atoms are the smallest unit of an element that can exist independently, all matter is made of them.
• The atoms subparticles are protons, neutrons, and electrons.
• Protons have a positive charge, neutrons have no charge, and electrons have a negative charge.
• All atoms of a given element have the same number of protons and neutrons in their nucleus.
• The number of protons is balanced by an equal number of electrons
• Electrons are negatively charged high energy particles with little or no mass
• Neutrons are neutral particles with little or no mass
• Electrons travel at very high speeds at various distances (energy levels) from the  nucleus
• Atoms can gain or lose electrons to form ions
• Anions are negatively charged because they gain electrons
• Cations are positively charged because they loose electrons
• The Law of Conservation of Mass states that matter cannot be created nor destroyed, only transformed into different forms.
• The atomic number determines the number of protons and electrons in an element.
• Protons & neutrons are found in the nucleus of an atom
• Electrons orbit around the nucleus of an atom
• Mass number = number of protons + number of neutrons
• Energy levels represent the area in an atom where an electron will be found
• Outer energy levels have more  energy than inner levels.
• Electrons in the last level are called valence electrons
• In the periodic table, elements are arranged by their atomic number
• (In the periodic table) Vertical columns=Groups  similar properties due to similar valence shells