7.1.11

Understanding Universal Indicator Paper

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Understanding Acids, Bases & Universal Indicator Paper

Universal indicator paper compares acidity, neutrality, or alkalinity by colour or pH. pH runs from 0 (strong acid) to pH 14 (strong base).

Characteristics of acids and bases

Characteristics of acids and bases

  • Acids taste sour and feel rough.
  • Bases taste bitter and feel slippery.
  • Both acids and bases react differently with universal indicator paper.
    • Acids increase hydrogen ion concentration in water.
    • Bases decrease hydrogen ion concentration by releasing hydroxide ions.
What is universal indicator paper?

What is universal indicator paper?

  • Universal indicator paper changes colour based on pH level.
  • It shows a range from red (acidic) to purple (alkaline).
    • Scientists use it to measure the strength of acids and bases.
    • The paper helps compare relative acidity and alkalinity quickly.
Using universal indicator paper

Using universal indicator paper

  • Dip the paper into a solution of acid or base.
  • Observe the colour change on the paper carefully.
  • Match the colour with the pH chart provided.
    • The pH scale runs from 0 to 14.
    • pH 7 shows neutrality; lower than 7 shows acidity; higher than 7 shows alkalinity.
Interpreting pH and colour results

Interpreting pH and colour results

  • Red or orange suggests high hydrogen ion concentration (strong acid).
  • Yellow or green shows weak acids or neutral solutions (like pure water).
  • Blue or purple means low hydrogen ion concentration (alkaline solution).
    • The closer the pH to 0, the stronger the acid.
    • The closer the pH to 14, the stronger the base.
Summary of key points

Summary of key points

  • Acids and bases show different colours on universal indicator paper.
  • Colour corresponds to the hydrogen ion concentration and pH.
  • Universal indicator paper offers a simple visual pH test.
  • The pH scale helps compare relative acidity and alkalinity.
Jump to other topics
1

States of Matter

1.1

Solids, Liquids, & Gases

1.1.1States of Matter - Solids, Liquids & Gases1.1.2Structure of Solids, Liquids & Gases1.1.3Changes of State1.1.4The Effects of Temperature & Pressure1.1.5Kinetic Theory1.1.6Kinetic Theory - Effects of Temperature & Pressure
1.2

Diffusion

1.2.1Diffusion1.2.2The Effect of Relative Molecular Mass
2

Atoms, Elements & Compounds

2.1

Elements, Compounds & Mixtures

2.1.1Differences Between Elements, Compounds & Mixtures
2.2

Atomic Structure & the Periodic Table

2.2.1The Structure of the Atom2.2.2Relative Charge, Mass & Atomic Numbers2.2.3Electronic Configuration of Elements
2.3

Isotopes

2.3.1Isotopes2.3.2Electronic Configuration of Isotopes2.3.3Calculating Relative Atomic Mass
2.4

Ions & Ionic Bonds

2.4.1Properties of Ionic Compounds - Structure & Bond2.4.2Formation of Ions & Ionic Bonds2.4.3Formation of Ionic Bonds - Metals & Non-Metals2.4.4Ionic Bonds2.4.5Ionic Compounds2.4.6Giant Lattice Structure of Ionic Compounds
2.5

Simple Molecules & Covalent Bonds

2.5.1Covalent Bonds2.5.2Formation of Covalent Bonds2.5.3Structure & Properties of Simple Molecules2.5.4Covalent Bonds in Simple Molecules2.5.5Properties of Simple Molecular Compounds
2.6

Giant Covalent Structures

2.6.1Giant Covalent Structures - Graphite2.6.2Giant Covalent Structures - Diamond2.6.3Uses of Graphite & Diamonds2.6.4Giant Covalent Structures - Silicon Oxide2.6.5Similarity Between Diamond & Silicon Oxide
2.7

Metallic Bonding

2.7.1Metallic Bonding2.7.2The Properties of Metals
3

Stoichometry

3.1

Formulae

3.1.1Understanding Formulae3.1.2Empirical Formula3.1.3Stoichiometry - Formulae, Word & Symbol Equations3.1.4Deduce & Write Ionic Compound Formulas
3.2

Relative Masses of Atoms & Molecules

3.2.1Relative Atomic Mass3.2.2Relative Molecular Mass (Mr)3.2.3Calculating Reacting Masses
3.3

The Mole & the Avogadro Constant

3.3.1Introducing Moles3.3.2Amounts of Substances3.3.3Moles & Equations3.3.4Calculations Involving Gases3.3.5Calculating Stoichiometric Reacting Masses3.3.6Calculating the Moles of Solute3.3.7Calculating Empirical Formula3.3.8Chemical Equations3.3.9Percentage Yield3.3.10Calculating Yield3.3.11Percentage Purity
4

Electrochemistry

4.1

Electrolysis

4.1.1Electrolytic Process4.1.2Electrolysis Examples4.1.3Electrolysis of a Binary Compound in Molten State4.1.4Electroplating4.1.5Transfer of Charge During Electrolysis4.1.6Electrolysis of Aqueous Solutions4.1.7Electrolysis of Copper Sulfate4.1.8Electrolysis of Halide Compounds4.1.9Half-Equations4.1.10Combustion of Hydrocarbons
4.2

Hydrogen–Oxygen Fuel Cells

4.2.1Fuel Cells4.2.2Hydrogen Fuel Cells4.2.3Comparing Hydrogen-Oxygen Fuel Cells & Petrol
5

Chemical Energetics

5.1

Exothermic & Endothermic Reactions

5.1.1Energy Conservation5.1.2Exothermic Reactions5.1.3Endothermic Reactions5.1.4Energy Change of a Reaction5.1.5Reaction Pathway Diagrams5.1.6Calculating Enthalpy Change
6

Chemical Reactions

6.1

Physical & Chemical Changes

6.1.1Difference btwn Physical & Chemical Changes
6.2

Rate of Reaction

6.2.1Collision Theory & Rate of Reaction6.2.2Factors Affecting Rate of Reaction6.2.3Investigating Rate of Reaction by Change in Mass6.2.4Investigating Rate - Formation of a Gas6.2.5Evaluating Methods to Investigate Reaction Rates
6.3

Reversible Reactions & Equilibrium

6.3.1Reversible Reactions6.3.2Conditions & Equilibrium6.3.3Dynamic Equilibrium6.3.4Changing Conditions - Heat & Water Effects6.3.5Factors Affecting Equilibria - Temperature6.3.6Factors Affecting Equilibria - Pressure6.3.7Factors Affecting Equilibria - Concentration6.3.8The Haber Process6.3.9The Haber Process Equation
6.4

Redox

6.4.1Redox Reactions6.4.2Redox Reactions - OIL RIG6.4.3Examples of Redox Reactions6.4.4Identifying Redox Reactions6.4.5Identifying Redox Reactions by Colour Changes6.4.6Testing for Oxidising & Reducing Agents
7

Acids, Bases & Salts

7.1

The Characteristic Properties of Acids & Bases

7.1.1Acids & Alkali7.1.2Reactions of Metals with Acids7.1.3Reactions of Bases with Acids7.1.4Reactions of Carbonates with Acids7.1.5Identifying Acids7.1.6Properties & Effects of Acids7.1.7Properties of Bases - Reactions with Acids & Salts7.1.8Properties of Alkalis & Indicators7.1.9Strong vs Weak Acids7.1.10Strong vs Weak Bases7.1.11Understanding Universal Indicator Paper7.1.12Acids, Bases & the Neutralisation Reaction
7.2

Oxides

7.2.1Oxides7.2.2Amphoteric Oxides - Reacting with Acids & Bases
7.3

Preparation of Salts

7.3.1Soluble Salts7.3.2Preparing Soluble Salts7.3.3Solubility of Salts7.3.4Preparing Insoluble Salts & Crystallisation
8

The Periodic Table

8.1

Arrangement of Elements

8.1.1The Periodic Table8.1.2Metals & Non-Metals
8.2

Group I Properties

8.2.1Alkali Metals8.2.2Alkali Metals - Properties8.2.3Reactivity of Alkali Metals8.2.4Alkali Metals & Water
8.3

Group VII Properties

8.3.1The Halogens - Properties8.3.2The Halogens - Colours & States8.3.3The Halogen - Displacement 18.3.4The Halogen - Displacement 2
8.4

Transition Elements

8.4.1Transition Metals8.4.2Transition Metals - Special Properties
8.5

Noble Gases

8.5.1Noble Gases - Properties
9

Metals

9.1

Properties of Metals

9.1.1Physical Properties of Metals9.1.2Chemical Properties of Metals9.1.3Metal Oxides
9.2

Uses of Metals

9.2.1Uses of Metals: Aluminium & Copper
9.3

Alloys & Their Properties

9.3.1Alloys9.3.2Alloys 29.3.3Alloys & their Uses in Everyday Life9.3.4Structural Diagrams of Alloys9.3.5Structure of Alloys & Their Strength
9.4

Reactivity Series

9.4.1Metals - Reactivity Series & Reactivity9.4.2Order of Reactivity9.4.3Reactivity of Metals
9.5

Corrosion of Metals

9.5.1Corrosion9.5.2Preventing Corrosion
9.6

Extraction of Metals

9.6.1Extraction of Metals9.6.2Extracting Iron9.6.3Extracting Aluminium from Bauxite
10

Chemistry of the Environment

10.1

Water

10.1.1Testing & Treating Water10.1.2Testing Water Purity Using Melting Point10.1.3Water from Natural Sources10.1.4Potable Water
10.2

Fertilisers

10.2.1Nitrogen & Fertilisers
10.3

Air Quality & Climate

10.3.1Gases in the Atmosphere10.3.2Common Atmospheric Pollutants10.3.3Consequences of Atmospheric Pollutants10.3.4Strategies to Reduce Pollution Effects10.3.5Photochemical Reactions10.3.6Car Engines, Nitrogen Oxides, & Converters
11

Organic Chemistry

11.1

Formulae, Functional Groups & Terminology

11.1.1Formula of a Molecule11.1.2General Formulae of Organic Compounds11.1.3Functional Groups11.1.4Homologous Series11.1.5Saturated & Unsaturated Organic Compounds11.1.6Structural Formula11.1.7Structural Isomers
11.2

Naming Organic Compounds

11.2.1Drawing Displayed Formulae11.2.2Naming Organic Compounds - Unbranched11.2.3Naming Unbranched Esters from Alcohols & Acids11.2.4Naming Structural Formulae
11.3

Fuels

11.3.1Fossil Fuels11.3.2Methane as the Main Constituent of Natural Gas11.3.3Fuels & Hydrocarbons11.3.4Petroleum - A Mixture of Hydrocarbons11.3.5Fractional Distillation11.3.6Fractions11.3.7Uses of Fractions - Fuels
11.4

Alkanes

11.4.1Alkanes11.4.2Properties of Alkanes11.4.3Substitution Reactions of Alkanes with Chlorine
11.5

Alkenes

11.5.1Alkenes11.5.2Shortest Alkenes11.5.3Reactions of Alkenes11.5.4Types of Alkene Reactions11.5.5Cracking11.5.6Testing Saturated & Unsaturated Hydrocarbons11.5.7Properties of Alkenes - Addition Reactions
11.6

Alcohols

11.6.1Alcohols11.6.2Smallest Alcohols11.6.3Fermentation11.6.4Steam11.6.5Fermentation vs Hydration of Ethene11.6.6Manufacture of Ethanol: Fermentation & Hydration11.6.7Combustion of Ethanol11.6.8Uses of Ethanol - Solvent & Fuel11.6.9Advantages & Disadvantages of Ethanol Manufacture
11.7

Carboxylic Acids

11.7.1Carboxylic Acids11.7.2Smallest Carboxylic Acids11.7.3Reactions of Carboxylic Acids11.7.4Formation of Ethanoic Acid
11.8

Polymers

11.8.1Polymers11.8.2Problems With Polymers11.8.3Polymers & Plastics11.8.4Problems with Plastics11.8.5Condensation Polymerisation11.8.6Condensation Polymerisation Examples11.8.7Addition Polymerisation11.8.8Addition Polymerisation Examples11.8.9Structure of Polymers11.8.10Natural Polyamides - Proteins & Amino Acids
12

Experimental Techniques & Chemical Analysis

12.1

Experimental Design

12.1.1Measurement Tools12.1.2Mixtures12.1.3Understanding Solvents, Solutes, & Solutions12.1.4Separating Mixtures12.1.5Distillation12.1.6Advantages & Disadvantages of Experimental Methods
12.2

Acid-base Titrations

12.2.1Acid-base Titrations
12.3

Chromatography

12.3.1Chromatography12.3.2Paper Chromatography12.3.3Chromatogram
12.4

Separation & Purification

12.4.1Purity12.4.2Methods of Separation & Purification
12.5

Identification of Ions & Gases

12.5.1Testing Aqueous Cations 112.5.2Testing Aqueous Cations 212.5.3Testing Cations - Flame Tests12.5.4Testing Cations12.5.5Testing for Aqueous Cations12.5.6Testing Anions - Sulfates12.5.7Testing Anions - Nitrates12.5.8Testing Gases - Hydrogen12.5.9Testing Gases - Oxygen12.5.10Testing Gases - Carbon Dioxide12.5.11Testing Gases - Chlorine12.5.12Identifying Gases

Practice questions on Understanding Universal Indicator Paper

Can you answer these? Test yourself with free interactive practice on Seneca — used by over 10 million students.

  1. 1
    Characteristics of acids and bases:Fill in the list
  2. 2
    What happens to the hydrogen ion concentration in water when an acid is present?Multiple choice
  3. 3
    A student tests an unknown liquid with universal indicator paper and observes that the paper turns red. Based on this observation, what can the student infer about the liquid's pH and ion concentration?Multiple choice
  4. 4
    When universal indicator paper is dipped into a solution and changes to green, what conclusion can the student draw about the solution's acidity or alkalinity?Multiple choice
  5. 5
    A chemist needs to compare the strength of two solutions, one producing an orange colour and the other a blue colour on universal indicator paper. How should the chemist interpret these colours in terms of pH and strength?Multiple choice
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Strong vs Weak Bases

Acids, Bases & the Neutralisation Reaction