Science Exam 2025

Types of Chemical Bonds

• Ionic Bond: A bond formed when a metal and a non-metal transfer electrons to each other. For example, Lithium Chloride (LiCl) is formed when lithium donates an electron to chlorine.

• Covalent Bond: A bond where two non-metals share electrons. An example is Hydrogen Oxide (H₂O), where hydrogen and oxygen share electrons to form water.

Properties of Matter

• Physical Property: Characteristics of a pure substance that can be observed without changing its chemical composition. Examples include color, boiling point, and density.

• Chemical Property: A property that describes a substance's ability to undergo chemical changes, such as reactivity with acids or bases.

Changes in Matter

• Physical Change: A transformation that alters the form of a substance but not its chemical identity, such as melting ice into water.

• Chemical Change: A process that results in the formation of one or more new substances, such as rust forming on iron.

Observational Techniques in Science

Types of Observations

• Qualitative Observation: Descriptive observations made using the five senses, such as noting the color or texture of a substance.

• Quantitative Observation: Observations that involve measurement and numerical data, such as measuring the temperature of a liquid.

Scientific Method Components

• Hypothesis: An educated guess or prediction that can be tested through experimentation.

• Conclusion: A summary based on evidence or facts gathered during an experiment.

Astronomy and the Universe

Celestial Bodies

• Terrestrial Planets: The inner planets of our solar system, which include Mercury, Venus, Earth, and Mars. These planets are rocky and have solid surfaces.

• Gas Giants: The outer planets, including Jupiter, Saturn, Uranus, and Neptune, characterized by their gaseous compositions and lack of solid surfaces.

Cosmic Phenomena

• Galaxy: A massive system of stars, dust, and gas bound together by gravity, such as the Milky Way.

• Meteor: A burning meteorite that enters Earth's atmosphere, creating a bright streak of light in the sky.

Energy Sources and Their Applications

Renewable and Non-Renewable Energy

• Hydroelectricity: Electricity generated by the movement of water, typically through dams.

• Solar Energy: Energy harnessed from the sun's rays, used for heating and electricity generation.

• Wind Energy: Energy produced from the movement of air, often captured by wind turbines.

• Biomass: Organic materials, such as plant matter, that are burned to produce heat or energy.

• Fossil Fuels: Natural resources like coal, oil, and natural gas that are burned for energy.

Electricity and Circuits

Electrical Concepts

• Voltage: The potential difference in electrical energy between two points, measured in volts.

• Current: The rate of flow of electric charge, measured in amperes (A).

• Resistance: The opposition to the flow of electric current, measured in ohms (Ω).

Circuit Calculations

• Series Circuit: In a series circuit, the current remains the same, while the voltage is the sum of the individual voltages across each component.

• Parallel Circuit: In a parallel circuit, the voltage remains the same across each branch, while the total current is the sum of the currents through each branch.

• Calculating Resistance: In a series circuit, resistances add up; in a parallel circuit, the total resistance can be calculated using the formula: 1/R_total = 1/R1 + 1/R2 + ... + 1/Rn.

Advanced Concepts in Physics

Cosmic Forces

• Dark Energy: A mysterious force that is believed to be causing the accelerated expansion of the universe, counteracting the force of gravity.

• Solar Phenomena: Events such as solar flares and prominences, which are bursts of gas from the sun's surface that can affect space weather.