A cube of material has sides of 1 nm. Calculate its surface area to volume ratio.

The ratio is 6, because the surface area is 6 nm² and the volume is 1 nm³.

Explain why a large surface area to volume ratio makes nanoparticles useful as catalysts.

A far greater fraction of their atoms lies on the surface, so many more reactant molecules can react at the same time.

Which nanoparticles are used in some sunscreens?

Titanium dioxide and zinc oxide nanoparticles are used.

Explain why nanoparticulate titanium dioxide is preferred to the ordinary powder in a sunscreen.

The nanoparticles are too small to scatter visible light, so the cream looks clear on the skin rather than white.

Edexcel GCSE Chemistry 1CH0

Key Concepts in Chemistry

Topic overview Formulae, word equations and balanced equations Hazard symbols and assessing risk The changing model of the atom Protons, neutrons and electrons The nucleus, mass number and atomic mass Elements and isotopes Calculating particle numbers and relative atomic mass Mendeleev's periodic table How the modern periodic table is arranged Electronic configuration and the periodic table How ionic bonds form Ions in ionic compounds Formulae of ionic compounds Naming compounds and the ionic lattice Covalent bonds and molecules Dot and cross diagrams for simple molecules Classifying substances and the properties of ionic compounds Properties of simple molecular substances, and forms of carbon Graphite and diamond Fullerenes and graphene Polymers and models of bonding The properties of metals Relative formula mass and percentage composition Empirical and molecular formulae Conservation of mass in closed and open systems Reacting masses from balanced equations Concentration in grams per cubic decimetre

States of Matter and Mixtures

Topic overview The three states of matter and changes of state Energy changes during changes of state, and predicting state Pure substances and melting point data Choosing a separation technique Separating a mixture in practice Paper chromatography and interpreting a chromatogram Investigating inks by distillation and chromatography Making water potable

Chemical Changes

Topic overview Acids, alkalis and the pH scale Indicators: litmus, methyl orange and phenolphthalein Investigating pH change when neutralising an acid Bases and alkalis Reactions of acids, and testing for hydrogen and carbon dioxide Neutralisation and its ionic equation Preparing soluble salts from insoluble and soluble reactants Preparing pure, dry copper sulfate crystals Carrying out an acid-alkali titration Solubility rules Predicting precipitates and preparing an insoluble salt Electrolytes and what electrolysis is Movement of ions and predicting the products of molten electrolysis Electrolysis with inert electrodes Electrolysis of copper sulfate solution Investigating the electrolysis of copper sulfate

Extracting Metals and Equilibria

Topic overview Investigating the reactivity of metals The reactivity series Ores, oxidation and reduction Choosing a method to extract a metal Corrosion resistance and recycling metals Life cycle assessment Reversible reactions and dynamic equilibrium The Haber process and its conditions

Transition Metals, Quantitative Chemistry and Industrial Processes

Topic overview Transition metals and their properties Corrosion and electroplating Preventing rusting Alloys and alloy steels How the uses of metals relate to their properties Carrying out an accurate titration Percentage yield Atom economy The Haber process Fertilisers and ammonium salts Preparing ammonium sulfate in the lab and in industry Chemical cells and fuel cells Evaluating fuel cells

Groups in the Periodic Table

Topic overview The groups of the periodic table, and the alkali metals Reactions of the alkali metals with water The pattern in alkali metal reactivity and why it happens Physical properties of the halogens The test for chlorine, and halogens reacting with metals Hydrogen halides, and explaining halogen reactivity Displacement reactions of the halogens Group 0: the noble gases

Rates of Reaction and Energy Changes

Topic overview Investigating the rate of a reaction Measuring rate and interpreting rate graphs Collision theory and factors affecting rate Catalysts and enzymes Exothermic and endothermic changes Bond breaking, bond making and the overall energy change Activation energy and reaction profiles

Fuels and Earth Science

Topic overview Hydrocarbons and crude oil Fractional distillation and the fractions Properties of the fractions and homologous series Complete and incomplete combustion Carbon monoxide and soot Pollutants and acid rain Hydrogen and fossil fuels compared Cracking and why it is necessary The Earth's early atmosphere How the oceans formed and how oxygen appeared The test for oxygen and the greenhouse gases Today's atmosphere and evidence for climate change

Chemical Analysis, Organic Chemistry and Materials

Uses and risks of nanoparticles

2 things to know
Paper 2

Overview

How surface area to volume ratio grows as particles shrink, why that suits catalysts and sunscreens, and the health and environmental risks that are not yet understood.

What you need to know

Answer each one before you reveal it.

Your recallNot started

Key term

What happens to the surface area to volume ratio of a particle as the particle gets smaller?

Numbers

A cube of material has sides of 2 nm. Calculate its surface area to volume ratio.

Questions from this subtopic

Each one with the model answer underneath.

1
What happens to the surface area to volume ratio of a particle as the particle gets smaller?
Model answer
The surface area to volume ratio increases.
2
A cube of material has sides of 2 nm. Calculate its surface area to volume ratio.
Model answer
The ratio is 3, because the surface area is 24 nm² and the volume is 8 nm³.
3
A cube of material has sides of 1 nm. Calculate its surface area to volume ratio.
Model answer
The ratio is 6, because the surface area is 6 nm² and the volume is 1 nm³.
4
Explain why a large surface area to volume ratio makes nanoparticles useful as catalysts.
Model answer
A far greater fraction of their atoms lies on the surface, so many more reactant molecules can react at the same time.
5
Which nanoparticles are used in some sunscreens?
Model answer
Titanium dioxide and zinc oxide nanoparticles are used.
6
Explain why nanoparticulate titanium dioxide is preferred to the ordinary powder in a sunscreen.
Model answer
The nanoparticles are too small to scatter visible light, so the cream looks clear on the skin rather than white.

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Key Concepts in Chemistry

States of Matter and Mixtures

Chemical Changes

Extracting Metals and Equilibria

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