Comprehensive GCSE Chemistry: Atomic Structure, Bonding, Organic Chemistry & Energy

Why is the perception of risk often different from measured risk?

Factors include voluntary vs imposed risks, familiar vs unfamiliar risks, and visible vs invisible hazards.

What is the importance of peer review in scientific research?

Peer review helps detect false claims and establishes a consensus about valid claims.

What is a limitation of scientific reports in popular media?

Reports are not subject to peer review and may be oversimplified, inaccurate, or biased.

What is the role of scientific theories in hypothesis development?

Use scientific theories and explanations to develop hypotheses.

How do you identify independent and dependent variables?

The independent variable is changed by the investigator, while the dependent variable is measured for each change.

What are control variables and why are they important?

Control variables are kept the same to ensure a fair test.

What is the importance of health and safety considerations in experiments?

To ensure the correct manipulation of apparatus and accuracy of measurements.

How can risks be reduced in practical contexts?

Suggest methods to minimize the risk of harm.

What is an appropriate sampling technique?

Suggest and describe a technique to ensure samples collected are representative.

How do you find the arithmetic mean of a set of data?

Add all the values together and divide by the number of values.

What is the purpose of constructing and interpreting frequency tables and diagrams?

To summarize and visualize data distributions.

What is an order of magnitude calculation?

It estimates the size of a value by rounding it to the nearest power of ten.

What does it mean to change the subject of an equation?

To rearrange the equation so that a different variable is isolated on one side.

How do you substitute numerical values into algebraic equations?

By replacing variables with their corresponding numerical values while using appropriate units.

What do the slope and intercept of a linear graph represent?

The slope indicates the rate of change, while the intercept shows the value when the independent variable is zero.

How is the slope of a tangent to a curve used in analysis?

It measures the rate of change at a specific point on the curve.

What does the area between a curve and the x-axis represent?

It represents the total value of the quantity over the interval, often measured by counting squares.

What does it mean to apply the idea of uncertainty in measurements?

It acknowledges that every measurement has some degree of error or variability.

How can the range of a set of measurements be used?

It serves as a measure of uncertainty by showing the spread of values around the mean.

What is the significance of recognizing patterns and trends in data?

It helps in making predictions and understanding relationships within the data.

What is the role of making inferences from observations?

To draw conclusions based on the data presented in various forms.

How should one evaluate data in terms of accuracy and precision?

Accuracy refers to how close measurements are to the true value, while precision refers to how closely measurements cluster together.

What distinguishes repeatability from reproducibility in measurements?

Repeatability refers to consistent results under the same conditions by the same investigator, while reproducibility refers to consistent results obtained by different investigators.

What are random errors and how can they be minimized?

Random errors cause unpredictable variations in results and can be reduced by taking multiple measurements and averaging them.

What is systematic error?

It is a consistent deviation from the true value in measurement results.

What should be done with anomalous values in data?

They should be examined to identify their cause and can be ignored if they result from poor measurement.

What is the importance of communicating scientific rationale in investigations?

It ensures that findings and conclusions are presented clearly and logically to support scientific understanding.

What are SI units and why are they important?

SI units are standardized units of measurement that provide consistency in scientific communication.

What is the purpose of using prefixes and powers of ten in scientific notation?

They simplify the representation of very large or very small numbers.

How can units be interconverted?

By using conversion factors that relate different units of measurement.

What is the smallest part of an element that can exist?

An atom.

How are atoms of each element represented?

By a chemical symbol, e.g., O for oxygen and Na for sodium.

How many different elements are there approximately?

About 100 different elements.

What is the purpose of the periodic table?

It provides a structured organization of the known chemical elements based on their physical and chemical properties.

What do compounds consist of?

Two or more elements chemically combined in fixed proportions.

How can compounds be separated into elements?

Only by chemical reactions.

What do chemical reactions involve?

The formation of one or more new substances and often a detectable energy change.

How can chemical reactions be represented?

By word equations or equations using symbols and formulae.

What is the historical significance of the periodic table?

It illustrates how scientific ideas and explanations develop over time as new evidence emerges.

What does the modern periodic table arrangement explain?

It is explained in terms of atomic structure, supporting the model of a nuclear atom with electrons in energy levels.

What is the relationship between chemical reactions and energy changes?

Chemical reactions often involve a detectable energy change.

What is the difference between atoms and compounds?

Atoms are the smallest units of elements, while compounds are formed from two or more elements chemically combined.

What is a mixture?

A mixture consists of two or more elements or compounds not chemically combined together.

What happens to the chemical properties of substances in a mixture?

The chemical properties of each substance remain unchanged.

What physical processes can separate mixtures?

Filtration, crystallisation, simple distillation, fractional distillation, and chromatography.

What is the significance of the processes used to separate mixtures?

These processes do not involve chemical reactions and no new substances are made.

What historical model of the atom existed before the discovery of the electron?

Atoms were thought to be tiny spheres that could not be divided.

What model of the atom was proposed after the discovery of the electron?

The plum pudding model.

What did the plum pudding model suggest about the atom?

The atom is a ball of positive charge with negative electrons embedded in it.

What conclusion was drawn from the alpha particle scattering experiment?

The mass of an atom is concentrated at the nucleus, which is charged.

Who adapted the nuclear model of the atom and how?

Niels Bohr suggested that electrons orbit the nucleus at specific distances.

What did later experiments reveal about the positive charge of the nucleus?

It could be subdivided into smaller particles, each with the same amount of positive charge, called protons.

Who provided evidence for the existence of neutrons?

James Chadwick.

What is the relative electrical charge of protons, neutrons, and electrons?

Protons have a positive charge, neutrons have no charge, and electrons have a negative charge.

What is the relationship between the number of protons and electrons in an atom?

The number of electrons is equal to the number of protons, resulting in no overall electrical charge.

What does the atomic number of an element represent?

The number of protons in an atom of that element.

How do atoms of different elements differ?

They have different numbers of protons.

What should students be able to describe using the nuclear model?

The structure of atoms.

What is the significance of new experimental evidence in scientific models?

It may lead to a scientific model being changed or replaced.

What is the approximate radius of an atom?

About 0.1 nm (1 x 10^-10 m)

How does the radius of a nucleus compare to that of an atom?

The radius of a nucleus is less than 1/10,000 of that of the atom, approximately 1 x 10^-14 m.

Where is most of the mass of an atom located?

Almost all of the mass of an atom is in the nucleus.

What is the mass number of an atom?

The sum of the protons and neutrons in an atom.

What are isotopes?

Atoms of the same element that have different numbers of neutrons.

How can you calculate the number of protons, neutrons, and electrons in an atom?

Given its atomic number and mass number.

What is relative atomic mass?

An average value that takes into account the abundance of the isotopes of an element.

How can you calculate the relative atomic mass of an element?

By using the percentage abundance of its isotopes.

What is the electronic structure of an atom?

The arrangement of electrons in the lowest available energy levels.

How can the electronic structure of sodium be represented?

As 2,8,1, indicating two electrons in the first shell, eight in the second, and one in the third.

How are elements arranged in the periodic table?

In order of atomic (proton) number and by groups with similar properties.

What do elements in the same group of the periodic table have in common?

They have the same number of electrons in their outer shell, giving them similar chemical properties.

What was a major limitation of early periodic tables?

They were incomplete and sometimes placed elements in inappropriate groups based on atomic weights.

Who is credited with overcoming some issues in the periodic table's development?

Dmitri Mendeleev.

What strategy did Mendeleev use to improve the periodic table?

He left gaps for undiscovered elements and rearranged some elements based on properties rather than strict atomic weights.

What knowledge helped explain the inaccuracies in the early periodic table based on atomic weights?

Knowledge of isotopes.

What defines metals in terms of ion formation?

Elements that react to form positive ions.

What defines non-metals in terms of ion formation?

Elements that do not form positive ions.

What is the significance of the periodic table being called 'periodic'?

Because similar properties occur at regular intervals.

What is the importance of using SI units and standard form in scientific measurements?

It ensures clarity and consistency in scientific communication.

What is the role of energy levels in an atom?

Electrons occupy the lowest available energy levels.

Where are metals located on the periodic table?

To the left and towards the bottom.

Where are non-metals located on the periodic table?

Towards the right and top.

What is a key characteristic of noble gases in Group 0?

They are unreactive and have stable arrangements of electrons.

How many electrons do noble gases have in their outer shell?

Eight electrons, except for helium which has two.

What trend is observed in the boiling points of noble gases?

Boiling points increase with increasing relative atomic mass down the group.

What are the elements in Group 1 of the periodic table called?

Alkali metals.

What is a characteristic property of alkali metals?

They have a single electron in their outer shell.

How does the reactivity of alkali metals change down the group?

Reactivity increases going down the group.

What are the elements in Group 7 of the periodic table known as?

Halogens.

What is a common characteristic of halogens?

They all have seven electrons in their outer shell.

What happens to the reactivity of halogens as you move down the group?

Reactivity decreases going down the group.

What type of molecules do halogens consist of?

Molecules made of pairs of atoms.

What is a key property of transition metals compared to Group 1 elements?

They have different melting points, densities, strength, hardness, and reactivity.

What are some typical properties of transition metals?

They have ions with different charges, form colored compounds, and are useful as catalysts.

What is the relationship between the arrangement of electrons and the reactions of elements?

The reactions are related to the arrangement of electrons in their atoms and their atomic number.

What is the significance of the outer shell of electrons for elements in Group 1?

Properties of the elements depend on the outer shell of electrons.

What can a more reactive halogen do to a less reactive halogen?

Displace it from an aqueous solution of its salt.

Which transition metals should students exemplify for their general properties?

Cr, Mn, Fe, Co, Ni, Cu.

What is the trend in relative molecular mass, melting point, and boiling point for halogens?

They increase going down the group.

What type of reactions are associated with the halogens?

Displacement reactions.