Before you read this, I suggest you read post 16.21. Let’s think about two identical steam engines; each contains water at the same temperature (100oC) at which water boils. The only difference is that one boiler is full and the other is only half full. Which of the two engines is capable of doing most… Continue reading 16.34 Temperature

Before you read this, I suggest you read posts 16.21 and 16.30. A chemical reaction occurs when atoms change the way in which they share electrons to form new molecules (see post 16.30). For example, a carbon atom (C) reacts with an oxygen molecule (O2) to form a molecule of carbon dioxide (O=C=O or CO2).… Continue reading 16.33 Chemical reactions

Many people are optimistic that science will find solutions to the problems that threaten us, like diseases, famines, depletion of natural resources etc. I am an optimist too. But I don’t believe that science can always provide the solution to such problems. For example, suppose I were offered $10billion to recruit a team of scientists… Continue reading 16.32 Faith in Science

Before you read this, I suggest you read posts 16.29 and 16.30. In post 16.30 we saw that the formation of molecules could be explained by atoms sharing pairs of electrons. This shared pair of electrons is called a chemical bond. If two atoms contribute one electron each, the bond is a covalent bond; if… Continue reading 16.31 Electrons in molecules

Before you read this post, I suggest you read posts 16.27 and 16.29 In post 16.29, we saw that electrons occupy atomic energy levels to minimise their overall energy. However, some electron configurations are more stable (they have a lower overall energy) than others. The evidence for this statement is that some atoms are much… Continue reading 16.30 Molecules

Before you read this, I suggest that you read posts 16.2, 16.21 and 16.27 We can measure the energy of electrons in atoms from the wavelengths at which elements (see post 16.27) absorb or emit light. The Danish physicist Niels Bohr explained these results using the quantum theory (see post 16.2) in which electrons are… Continue reading 16.29 Electrons in atoms

Before you read this, I suggest that you read posts 16.24 and 16.26. In this post I want to explore how we make decisions based on experimental results. Suppose two groups of rats, are identical in all respects, eat the same diet and live in identical conditions. However, one group is given a dietary supplement… Continue reading 16.28 Significant differences

I suggest that you read post 16.25 on electrical charge before you read this. The ancient Greek philosopher Democritus believed that you couldn’t keep breaking stuff into smaller and smaller bits – there must be a limit. He called these smallest bits of stuff atoms. I’m not convinced by the logic of his argument (see… Continue reading 16.27 Atoms

Before you read this, I suggest you read post 16.24. If you repeat an experiment several times, you will get slightly different results because of random effects beyond your control. For example, if you measure the temperature at which a liquid boils, you may get slightly different results because of changes in atmospheric pressure –… Continue reading 16.26 Normal distribution

Before you read this, I suggest you read posts 16.4 and 16.16. In post 16.16 we met the concept of a gravitational field. Are there other kinds of fields? Yes – two that we encounter in everyday life are the electric field and the magnetic field. Both arise because some objects can have a property… Continue reading 16.25 Electrical charge