586 sبه‌رهه‌می گه‌ڕانه‌که وا لێی نزیکه Physics 1
شێوه‌کاریه‌کان
- Gravity Force Lab (HTML5)
- States of Matter (HTML5)
- بارستایی & سپرینگ
- بارگەکان و بوارەکان (HTML5)
- بینینی ڕەنگەکان (HTML5)
- بەیەکداچوونی شەپۆل (HTML5)
- تاقیگه‌ی بارگه‌گر
- تاقیگەی بارگەگری - سەرەتایی (HTML5)
- تاقیگەی بەریەککەوتن (HTML5)
- تاقیگەی دروست کردنی سوڕی کارەبایی - گۆڕدراو (HTML5)
- تاقیگەی هێزی کێشکردن - سەرەتایی (HTML5)
- توانای گه‌یاندن
- جۆره‌كانی وزه و گۆڕانیان (HTML5)
- دروستکردنی سوڕی کارەبایی نەگۆڕ (HTML5)
- تاقیگەی دروستکردنی سوڕی کارەبایی نەگۆڕ (HTML5)
- دروست کردنی سوڕی کارەبایی گۆڕاوو (HTML5)
- دروستکردنی ڕووبەر بە شێوازی دەیانە (HTML5)
- شکانەوەی ڕووناکی (HTML5)
- شەبەنگی تەنی ڕەش (HTML5)
- شەپۆل لەسەر دەزوو (HTML5)
- لە ژێر پەستان (HTML5)
- میزەڵدان و بارگەی نەجووڵاو (HTML5)
- ناساندنێکی سەرتایی شەپۆل (HTML5)
- ناوک دروست بکە (HTML5)
- هاوسەنگ کردنی تەنەکان (HTML5)
- پارکی وزە (HTML5)
- پەرژبوونەوەی ڕەزەرفۆرد (HTML5)
- چڕی (HTML5)
- ڤۆڵتیە (HTML5)
- کارلێکی نێوان گەردیلەکان (HTML5)
- کۆکردنەوەی ڤێکتەرەکان (HTML5)
- گەردیلە دروست بکە (HTML5)
- یاسای ئۆم (HTML5)
- یاسای هوک (HTML5)
- یاسای کوڵۆم (HTML5)
- States of Matter: Basics (HTML5)
- Pendulum Lab (HTML5)
- Alpha Decay
- Balloons and Static Electricity
- Balloons & Buoyancy
- Band Structure
- Battery-Resistor Circuit
- Battery Voltage
- Beta Decay
- Quantum Bound States
- Buoyancy
- Calculus Grapher (HTML5)
- Double Wells and Covalent Bonds
- Curve Fitting (HTML5)
- Davisson-Germer: Electron Diffraction
- Diffusion (HTML5)
- Neon Lights & Other Discharge Lamps
- Electric Field of Dreams
- Electric Field Hockey
- Energy Skate Park: Basics (HTML5)
- Faraday's Electromagnetic Lab
- Faraday's Law (HTML5)
- Fluid Pressure and Flow
- Forces in 1 Dimension
- Forces and Motion
- Forces and Motion: Basics (HTML5)
- Fourier: Making Waves (HTML5)
- Fourier: Making Waves
- Fractions: Mixed Numbers (HTML5)
- Friction (HTML5)
- Gases Intro (HTML5)
- Gas Properties (HTML5)
- Generator
- Geometric Optics (HTML5)
- Geometric Optics: Basics (HTML5)
- Gravity and Orbits (HTML5)
- The Greenhouse Effect
- Models of the Hydrogen Atom
- Kepler's Laws (HTML5)
- Ladybug Motion 2D
- Lasers
- Lunar Lander
- Magnet and Compass
- Magnets and Electromagnets
- Masses and Springs (HTML5)
- Masses and Springs: Basics (HTML5)
- Maze Game
- Microwaves
- Molecular Motors
- Molecules and Light (HTML5)
- Motion in 2D
- The Moving Man
- Simplified MRI
- My Solar System (HTML5)
- Normal Modes
- Nuclear Fission
- Optical Quantum Control
- Optical Tweezers and Applications
- Photoelectric Effect
- Plinko Probability (HTML5)
- Projectile Data Lab (HTML5)
- Projectile Motion (HTML5)
- Quantum Tunneling and Wave Packets
- Quantum Wave Interference
- Radiating Charge
- Radioactive Dating Game
- Radio Waves & Electromagnetic Fields
- Ramp: Forces and Motion
- Reactions & Rates
- Resistance in a Wire (HTML5)
- Resonance
- Reversible Reactions
- Ladybug Revolution
- Semiconductors
- Signal Circuit
- Sound
- Stern-Gerlach Experiment
- Stretching DNA
- The Ramp
- Torque
- John Travoltage
چالاکیه‌کان
- Projectile Motion - Physics 1 lab experiment
- Projectile Motion - Physics 1 Lab
- The physics of the triple jump
- Maze Game 1: Using vector representations to move through a maze (Inquiry Based)
- My mystery number
- Springs and Things
- Concept questions for Physics using PhET (Inquiry Based)
- Drag and count
- Family of Mr. 10
- Balancing Act Homework Activity 1 and 2
- Mapping of PhET and IBDP Physics
- Vectors for Physics 1
- Activity: My Solar System for APP1
- PhET Simulations Aligned for AP Physics C
- Pendulum Inquiry and Lab Report
- Ten and how many more?
- Chaos Physics
- Conservation of Energy 1: Introduction (qualitative approach)
- Projectile Motion
- Day 1: Lighting a Bulb
- Guided Discovery (Chinese/English) for Freshman University Physics: 2. Newtonian Mechanics
- Algebra-based Physics Semester one lessons, clicker questions, and schedule in pdf (Inquiry Based)
- Pendulum Lab 1: Intro to pendulum (Inquiry Based)
- Guided Discovery (Chinese/English) for Freshman University Physics: 1. Kinematics
- Estados de la Materia
- Discovering Newton's Second Law
- Roller Coaster Physics Investigation
- D.C Circuit Simulation 1
- การทดลองที่ 6 คลื่นในเส้นเชือก
- Simple Pendulum
- Hook's Law
- Exploring Equivalence with Rational Numbers: Part 1 Fractions less than or equal to 1
- Reflection and Transmission Interactive Lecture
- Energy Skate Park Formal Lab
- การทดลองที่ 11 วงจรไฟฟ้ากระแสตรง
- Vector Addition 1: Introduction to vector math (Inquiry Based)
- Circuit 1 Properties of Electric Circuits (Inquiry Based)
- Reactions and Rates 1 Introduction to reactions (Inquiry Based)
- Salts and Solubility 1: introduction to salts (Inquiry Based)
- Free-Fall and Projectile Motion
- physics is fun
- Forces in 1 Dimension
- Circuit Lab 1 - Properties of Electric Circuits
- Swinging Physics Using Pendulum Phet
- Testing Ideas from Classical and Quantum Physics
- Horizontal projectile motion
- Forces in 1 and 2 Dimensions
- Waves on a String HTML5 PreAP Lesson
- What is a Fraction? Day 1 of 3
- Circuit 1 Properties of electric Circuits using only CCK(Inquiry Based)
- Forces and Motion activity 1: Predicting speed and directions changes (Inquiry Based)
- Reactants, Products and Leftovers Activity 1: Intro to Chemical Reactions and Limiting Reactants
- Ramp Activity 1: Using free body diagrams for motion on an incline (Inquiry Based)
- Physics Graphing and Introduction to Models
- MYP Physics: Gravitational force vs. Distance
- AP Physics Orbit Lab
- AP Physics PhET Projectile Motion Lab
- Universal Gravity-building formula, quantitative with graphing
- Collision investigation lab
- Regents Physics- Projectile Motion Intro
- MYP Physics: Electric Force vs. Distance
- Spring Force, Spring Constant and Elastic Potential Energy
- Force-time graph activity
- Maze Game- A Velocity & Acceleration Comparison
- Designing Experiments Using Masses & Springs
- Projectile Motion (Lab Report)
- Conservation of Mechanical Energy
- Gravity Force Lab PreAP using HTML5 Sim
- Density Exploration
- (BNCC) Cores, Coelhos e Lobos: o mais forte sobrevive? - Parte 1
- DC Circuit Lab
- LKS HUKUM HOOKE
- Rangkaian Kapasitor Zoewono
- LKS Kapasitor
- AYUNAN SEDERHANA
- Hubungan Antara Tegangan, Kuat Arus Dan Hambatan Listrik
- PEMANTULAN
- pH ASAM BASA
- Getaran
- LKS HUKUM HOOKE
- percobaan interferensi dengan berbantuan program phet
- vectors
- Applied Forces and Friction and a Review of Newton's 1st and 2nd Law
- Conservation of Energy Exploration with Skatepark Physics
- Water Waves in an Electric Sink
- Exploring Newton
- FRICTION_FORCES_in_1_dimension
- Hukum Ohm
- ΑΠΛΑ ΚΥΚΛΩΜΑΤΑ ΣΥΝΕΧΟΥΣ ΡΕΥΜΑΤΟΣ ΜΕ ΤΟ ΕΙΚΟΝΙΚΟ ΕΡΓΑΣΤΗΡΙΟ CIRCUIT CONSTRUCTION KIT ΤΟΥ PhET COLORADO
- การทดลองOnline 1 เรื่อง ลูกตุ้มนาฬิกาอย่างง่าย
- Net Forces and Newton's Second Law
- Introduction to Forces in 1-D
- Force introduction
- Discovering Newton's Second Law
- Comparing Forces on Different Planets
- Exploring Newtons' Second Law
- חקר כוח חיכוך
- Force of Friction Graphing Ff=(mu)Fn
- motion along straight line with constant speed
- motion along straight line with constant speed
- Proving Newton's Second Law
- Interactive Photoelectric Effect Lab
- AP Physics Gravity Lab
- Physics Lab Worksheet Momentum.docx
- Função do 1° grau
- Photoelectric Effect Phet Worksheet (AP Physics 2)
- Discovering the conservation of momentum
- Gravity Force Lab
- Potential Difference in Circuits
- PhET Energy Skate park
- Petunjuk Praktikum Kimia Umum 1 (Stoikiometri)
- Compendio de Actividades e ILDs basadas en simulaciones PhET
- การบวกลบเวกเตอร์
- LAB การสะท้อนและการหักเหแสง
- LAB การต่อแบตเตอรีและการประยุกต์ใช้งาน
- C.A.S.T.L.E. Unit 1 Labs
- Balancing act 1
- Forca dhe levizja 1
- Exploring Gravitation
- vector addition
- My Solar System
- Gas Properties Phet Simulation worksheet (AP Physics 2)
- High School Chemistry 1 level Balancing Equations
- PHET Charges and Fields Activity Part 1
- Level 1 - Momentum Lab by Stephen N. Clontz, M. Ed.
- PhET Collision Lab
- Kinetic Molecular Theory- Introduction (inquiry-based)
- Circuit Construction Kit
- Waves on a String AP1
- Vector addition worksheet
- Inclinação e Intersecção
- LR Lab with Simulation Part 1
- 1 Dimensional Motion - Kinematics and Graphing
- Waves Virtual Lab Part 1
- Newtons 1. und 2. Gesetz
- Undergrad MRI Workshop Activity
- Force and Motion
- 大一物理引導式自我發現 (中文/英文): 動力學 (牛頓定律)
- Exploring the Energy Skate Park
- Guided Discovery (Chinese/English) for Freshman University Physics: 5. Introduction to Waves
- Guided Discovery (Chinese/English) for Freshman University Physics: 6. Wave Interference
- Guided Discovery (Chinese/English) for Freshman University Physics: 3. Energy & Momentum
- Guided Discovery (Chinese/English) for Freshman University Physics: 4. Rotations & Oscillations
- Computer Simulations as a Tool to Assist Teaching Basics of Electromagnetism (Simulações Computacionais Como Ferramenta Auxiliar ao Ensino de Conceitos Básicos de Eletromagnetismo)
- Fluid Pressure and Flow Phet Simulation worksheet
- 2D Collision Lab
- Lab: Capacitance
- Projectile motion
- Magnetism
- Friction Experiment
- Virtual Lab
- Capacitor Lab: Basics: Inquiry into Capacitor Design
- Vector Addition Worksheet
- Vectors worksheet
- PhET Lab States of Matter Basics
- Horizontal Launch Investigation
- Ispitivanje fotoelektricnog efekta pomocu PhET simulacije
- Davisson Germer lecture and homework
- Alpha Decay investigations
- High School Chemistry 1 level: Limiting reagents
- Balancing Chemical Equations - Guided Inquiry Activity
- Quest for the Coulomb Cup
- Finding Wave Properties
- Lab: Electric Field & Electric Potential
- The Two-Plate Special
- Hooke's Law inquiry lab
- Middle School - Electric Circuits
- Middle School - series and parallel circuits
- Projectile motion worksheet
- Projectile Motion Experiments
- Gases Understanding physical properties of gases (Inquiry Based)
- Coeficientes e raízes das Funções do 1° e 2° Grau
- UNIDAD 1 S7 L12 Cambios de energía -Introducción
- UNIDAD 1 S3 L1 MOVIMIENTO ONDULATORIO (ONDAS MECÁNICAS)
- Isotopes and Atomic Mass - Guided Inquiry Activity
- Electrolyte and Non-electrolyte Solutions - Interactive Lecture Demonstration
- Molecule Polarity - Guided Inquiry Activity
- Beer's Law Warm-Up
- States of Matter Lecture Demonstration
- EM wave analogy tutorial
- Density-introduction
- Electrostatics Simulation lab
- Introduction to Discharge Lamps
- How to make a laser
- Understanding the Photoelectric Effect
- Wave Particle Duality
- Intro to Photoelectric Effect Interactive Lecture
- Probability and Randomness Interactive Lecture
- The Photoelectric Effect and Work Functions
- Rutherford Experiment
- Under Pressure
- Beta Decay Investigations
- Circuit activity 3 Combination Circuits (Inquiry Based)
- Circuit Lab 2 - Series and Parallel Circuits
- Atomic models homework (Inquiry based)
- Mapping Electric Fields
- Forces and Motion: Finding the Mass of a Car
- 'Lectronic Plates
- Bouncing Off the Walls
- Pixel Peeping
- Cavendish Lab
- Climate Change - Gas
- Gravity Force Lab Guided Inquiry
- Net force
- Linear momentum
- Projectile motion
- Projectile Motion
- Vector Addition
- projectile motion
- PhET Lab Energy Skate Park 2
- Milk Trucks
- Guided lab with instructions, screenshots and questions
- MRI lecture and homework
- Stern Gerlach clicker questions
- Types of Forces Investigation
- Waves Interference Remote Labs
- MS and HS TEK to Sim Alignment
- Modeling Paradigm Lab- 2nd Law
- (BNCC) Flutua ou Afunda? Um ensaio sobre a densidade dos materiais - Parte 1
- Saturated Solutions - Interactive Lecture Demonstration
- Investigation of a Solution’s Color (Qualitative and Quantitative) - Guided Inquiry Activity
- Plate Tectonics
- Salts and Solubility 5: Designer Salts (Inquiry Based)
- Build an Atom
- Waves Intro Remote Lab
- Energy Skate Park - Concept Questions Compendium
- Build a Molecule - Molecular Formulas and Coefficients
- Fuerzas en una rampa (actividad de indagación)
- Intro y laboratorio virtual de Tiro Parabólico
- Pushing Things Around
- Greased Lightning
- Fluid Experiments
- Projectile Motion - developing understanding.
- Projectile Motion
- The Ramp Mechanical Advantage and Efficiency
- Projectile Motion
- Energy Skate Park Lab Questions
- Worlds of Wonder
- Simple Pendulum
- Lab Photoelectric Effect
- Energy Chains
- projectile motion
- Exploring Equivalence with Rational Numbers: Part 2 Extending to Mixed Numbers
- Build an Atom - Guided-Inquiry Activity
- Salts and Solubility 3: Solution Equilibrium and Ksp (Inquiry Based)
- Wave Modeling and Wave addition (Inquiry Based)
- Presión hidrostática por indagación
- construye una Molécula - Formulas moleculares y coeficientes
- Formulas y nombres de moléculas
- ¿Qué tan bien la curva describe los datos?
- Densidad, actividad con la simulación
- pH Scale
- Radioactive Decay, Fission and Chain Reactions
- Movimiento en dos dimensiones: Caso del Proyectil (Two dimensions movement, projectile case).
- Experiencia Educativa Principio Arquimedes, Fuerza Boyante y Densidad (Learning experience: Archimedes principle, Buoyant force & Density).
- PhET Energy Forms and Changes Virtual Lab
- Projectile Motion Discovery
- Simple Pendulum Investigation Lesson Plan
- Energy Skate Park Lab (html5)
- Energy Simulation
- Ενεργειακά Διαγράμματα
- Bending Light Student Worksheet
- Crash!
- Photoelectric Effect
- Exploring Fission (inquiry)
- Forces and Newton's Laws Review
- Bose-Einstein Condensation Lesson
- Fractions 3 Day Unit
- Salts and Solubility 4: Using Q and LeChateliers Principle
- Escala de pH, introducción a ácidos y bases con indagación
- Introduction to Inequalities
- Intro: Gravedad y Orbitas
- Balance in the up-and-down
- Kinematics
- Blackbody Spectrum
- Conservation of Energy (Energy Skate Park)
- Current in DC Circuits
- Introduction to Fourier Analysis
- Build an Atom
- Experimental Design with Forces
- Gravity and Orbits Lesson
- Fracciones Equivalentes
- Explorando el equilibrio
- Indagación con la clase entera: Ley de Beer & Lambert
- Introducción a los estados de la materia
- Introduzione ai vettori
- Introduction to vectors
- Arithmetic mean with PhET and GeoGebra
- Exploring integers
- Exploración cuantitativa de la Fuerza de Gravedad
- Projectile Motion Lab
- Kinetic Molecular Theory
- Electric fields
- Investigating waves
- D.C Circuit Simulation 2 - Series and Parallel
- Lunar Lander/ Fun Game
- Electromagnetic Generation - Phet simulation
- Electromagnetic Induction
- Making STABLE Atoms Lab
- Pendulum Lab
- Projectile Motion Simulator
- Lesson plan
- Vector Addition Worksheet
- Photoelectric Effect
- Projectile Motion
- Quantitative Predictions of Projectile Motion
- Momentum Lab
- Projectile motion and horizontal component of its velocity
- Chemistry Theater
- Waves on a String and Wave Interference Virtual Labs
- Energy Skate Park Basics Lesson
- Balloons and Static Electricity
- Energia cinetica e potenziale
- Density Lesson (with Putty Lab)
- Hot Air Balloons Lesson
- Driven Oscillation
- Balancing Chemical Reactions Game
- Air Resistance Lesson
- Exploring parallel and perpendicular lines
- Električni otpor i Ohmov zakon
- PRIMARIA: Alineación con programas de la SEP México (2011 y 2017)
- Investigación del color de una solución (cualitativa y cuantitativa) - Actividad de consulta guiada
- fuerzas sobre un resorte
- Energía mecánica
- Introducción al movimiento del péndulo
- Equilibrio en el sube y baja
- explorando ondas en una cuerda
- Introducción a las colisiones
- Energía térmica y cambios de estados
- Hablemos de temperatura
- Fenomenos magnéticos
- Explorando circuitos CD
- Sonidos altos y bajos
- Reflexión y refracción de la luz
- Explorando circuitos RLC
- Explorando variables de la electricidad
- Explorando el funcionamiento de un condensador
- Explorando enteros
- Media artimética con PhET y GeoGebra
- Introducción a los vectores
- Explorando fracciones
- Leyes de Kirchhoff
- Ley de Coulomb
- Parametros Estadisticos
- Algoritimo da Adição usando o simulador PhET Faça um dez.
- Juego de numeros
- Asociacion de capacitores
- Fuerzas sobre un resorte II
- Aparatos de medicion electricos
- Bailando al son de las razones
- Matemáticas futboleras ¿y la mediana?
- Una torta de jamón con fracciones
- A física do salto triplo
- La fisica del salto triplo
- Introduccion al campo eléctrico
- Introduction aux vecteurs
- La Física del salto triple
- Introdução aos vetores
- Équilibre de la balançoire
- La physique du triple saut
- Equilíbrio na gangorra
- Equilibrio in su-e-giù
- Parliamo di temperatura
- Moving Man I: Velocity vs. Time Graphs
- Moving Man II: Acceleration vs. Time
- Ohm's Law, Kirchhoff's Laws, Resistors in Parallel and Series Lab
- Projectiles Air Resistance - It's a Drag
- Radio Waves & Electromagnetic Fields Simulation Homework
- Microwaves Simulation Activity
- Microwaves Simulation Homework
- Introduction to Energy Model
- Coulomb's Law for Chemistry
- Charges and Fields
- Percobaan gelombang pada tali
- Magnets, Electromagnets and Ohm's Law Lab!
- Forces and Motion Lesson
- simple pendulum lap
- Lab Experiment
- Simple Pendulum
- Natural Selection Lesson by UTeach
- vectors
- Explorando líneas paralelas y perpendiculares
- Hoja de Actividades de Ciencias: Soluciones Ácido Base
- Static Pressure
- Photoelectric Effect
- SECUNDARIA: Alineación PhET con programas de la SEP México (2011 y 2017)
- PREPARATORIA: Alineación de PhET con programas de la DGB México (2017)
- Modeling Gravity
- Moving Man Motion Graph Review
- Circuit Principles and Applications
- Projectile launch angle vs displacement
- Sound Simulation Homework II
- Addition and Resolution of Vectors
- Charges and Charged Objects Investigation
- Hooke's Law and Spring Constant with Energy: Regular Level
- Horizontal Projectile Motion
- Greenhouse effect activity
- The Greenhouse Effect PhET Simulation Lab
- Charges and Fields Exploration
- Guided Manual-Worksheet of ideal gas
- Second Law Inquiry PhET Forces and Motion
- Virtual Lab - Investigating Refraction of Light
- motion along straight line with constant acceleration
- Resistance and Resistivity
- Introdução a Geometria molecular
- Vectors Addition
- Potential Energy of A Spring (Elastic Potential Energy)
- Serie de Labs virtuales de Ondas
- Laboratorio Virtual de Visión del Color
- Waves on a String Discovery Activity
- Beer's Law Lab: Introduction to Beer's Law
- Construire un atome
- Getaran Harmonik Sederhana Pada Pegas
- The x and y's of Gas Properties
- Guided Manual-Worksheet of ideal gas
- Plinko Probability for Long-Run Frequencies
- Solubilidad
- Undersøgelse til Stoftilstande Basis
- Undersöka syra-bas-lösningar
- Introducción a Circuitos Eléctricos
- Serie de actividades para Electrostática: de Electrización, Campos y Fuerzas
- Laboratorio virtual de reflexión y refracción de la luz
- project motion
- Projectile Motion
- Turning Forces
- Density
- Using the Gases Intro PhET Simulation: Concept Development for Understanding Gas Laws and the Variable Changes Associated with Them
- Forces and Motion- Effects of Forces on Motion (Investigation)
- Isótopos y Masa Atómica: Actividad de Consulta Guiada
- Laboratorio virtual de Condensadores
- Transcripción y Traducción
- Vector Activity
- The Two-Slit Experiment
- Activity: Wave on a String
- Resistivity in a wire
- Rubric for Simple Pendulums - What Affects the Period?
- How do PhET simulations fit in my middle school program?
- Graphing Energy at the Skate Park
- Electric Field Hockey Post-Game Analysis
- El ruido y la contaminación acústica en mi ciudad
- Kracht en Beweging. Google Quizen
- Moving Man with Position and Velocity graphs
- Maze Game
- Intro to Circuits
- Kennismaken met bewegingsdiagrammen en versnelling
- Laboratorio de capacitores con y sin dieléctrico.
- Virtual Lab - Circuit Basics
- Soluciones: Unidades de Concentración
- Atividade de Força e Movimento
- PHET energy forms and changes simulation worksheet to accompany simulation
- Hooke's law
- Construye un átomo (indagación)
- Laboratorio virtuale di circuiti
- projectile motion worksheet
- Waves Virtual Lab Part 2
- Preguntas conceptuales: Neurona
- Using the Coulomb’s Law PhET Simulation: Concept Development for Understanding Electrostatic Forces
- Hojas de trabajo y preguntas sobre Energía
- States of Matter - Lab Simulation - student procedures and questions
- Projectile Motion Lab #2
- Tectónica de placas e a abertura e expansão do fundo dos oceanos.
- Cinco Numeritos para Jugar
- Multiplica la imaginacion
- Online Assignment 4 Ms & Ss
- Energiebehoud in het skatepark klas 5
- Cirkelbeweging inleiding
- Coulomb's Law Data Collection and Analysis (remote online learning)
- Zekering gebruiken als beveiliging tegen Kortsluiting en overbelasting.
- 大一物理引導式自我發現 (中文/英文): 運動學
- Medición del Ph de sustancias ácidas y básicas