Acids, Bases, Forces, Motion and Waves

• Study notes for Acids, Bases, Forces, Motion, Waves, Sound Waves, and Heat Transfer.

Acids and Bases

• Acids release hydrogen ions (H⁺) in water.
• Acids taste sour.
• Acids are corrosive to metals and skin.
• Acids turn blue litmus paper red.
• Acids have a pH less than 7.
• Examples of acids include lemon juice, vinegar, and stomach acid.
• Acids react with metals to produce hydrogen gas.
• Bases release hydroxide ions (OH⁻) in water.
• Bases taste bitter.
• Bases feel slippery.
• Bases turn red litmus paper blue.
• Bases have a pH greater than 7.
• Examples of bases include soap, baking soda, and bleach.
• Neutralization is a chemical reaction where an acid and a base react to form salt and water.
• An example of neutralisation is: HCl + NaOH → NaCl + H₂O.
• Indicators are chemicals that change color to indicate pH level.
• Examples of indicators include litmus paper, phenolphthalein, and universal indicator.
• The pH scale ranges from 0-14.
• Acids have a pH range of 0-6.
• Neutral substances have a pH of 7.
• Bases have a pH range of 8-14.

Forces

• A force is a push or pull on an object.
• Balanced forces cancel each other out, resulting in no change in motion.
• An example of balanced forces is a book resting on a table.
• Unbalanced forces do not cancel each other out, causing a change in motion.
• An example of unbalanced forces is a person pushing a cart.
• Newton’s First Law of Motion (Law of Inertia): An object at rest stays at rest, and an object in motion stays in motion unless acted upon by an external force.
• Newton’s Second Law of Motion (Law of Acceleration): The acceleration of an object depends on its mass and the applied force.
• The formula for Newton's Second Law of Motion is: Force = Mass × Acceleration (F = ma).
• Newton’s Third Law of Motion (Law of Action-Reaction): For every action, there is an equal and opposite reaction.

Motion

• Motion is a change in position over time.
• Distance is the total length of the path traveled (scalar quantity, measured in meters).
• Displacement is the shortest straight-line distance from the starting point to the endpoint (vector quantity).
• Speed is the rate at which an object moves.
• The formula for speed is: Speed = Distance ÷ Time (unit: m/s).
• Velocity is speed with direction.
• The formula for velocity is: Velocity = Displacement ÷ Time.
• Acceleration is the rate of change of velocity over time.
• The formula for acceleration is: Acceleration = (Final velocity - Initial velocity) ÷ Time (unit: m/s²).
• In a Distance-Time Graph: A straight line indicates constant speed, and a curved line indicates acceleration.
• In a Velocity-Time Graph: A horizontal line indicates constant velocity, and a sloped line indicates acceleration or deceleration.

Waves and Sound Waves

• A wave is a disturbance that transfers energy from one place to another.
• Mechanical waves require a medium to travel (e.g., sound, water waves, seismic waves).
• Transverse waves: Particles move perpendicular to wave direction (e.g., water waves, light waves).
• Longitudinal waves: Particles move parallel to wave direction (e.g., sound waves, seismic P-waves).
• Electromagnetic waves do not require a medium and can travel through space (e.g., light, radio waves, X-rays).
• Sound waves travel through solids, liquids, and gases.
• Sound waves travel fastest in solids and slowest in gases.
• Frequency: Number of waves per second, determines pitch (high frequency = high pitch, low frequency = low pitch).
• Amplitude: Height of the wave, determines loudness (greater amplitude = louder sound).
• Wavelength: Distance between two corresponding points of a wave.
• Reflection: Bouncing back of sound (echo).
• Refraction: Bending of sound waves as they pass through different mediums.
• Absorption: When sound is taken in by a surface, reducing echo.

Heat Transfer

• Heat is the transfer of thermal energy from one object to another due to temperature differences.
• Conduction is the transfer of heat through direct contact and occurs best in solids (e.g., metal spoon in hot soup).
• Convection is the transfer of heat through fluid movement (liquids or gases).
• Hot fluids rise, cool fluids sink (e.g., boiling water, sea breeze, lava lamp).
• Radiation is the transfer of heat through electromagnetic waves and requires no medium (e.g., sunlight warming the Earth, heat from a fire).
• Thermal conductors allow heat to pass through easily (e.g., metals like copper and aluminum).
• Insulators prevent heat transfer (e.g., wood, wool, plastic, air).