Before you read this, I suggest you read posts 16.34, 16.35 and 16.37. In post 16.34 entropy was introduced as the quantity of heat flowing into an object divided by its temperature (on the Kelvin scale). This definition leads to the idea that the entropy of a closed system tends to increase spontaneously. The idea… Continue reading 16.38 Entropy and disorder

Before you read this, I suggest that you read posts 16.34 and 16.35. We all have everyday experience of solids, liquids and gases. We can hit things with solids but may need to be careful that they don’t break. We need to keep liquids in a cup, jar, bottle or similar container. Liquids differ from… Continue reading 16.37 Solids, liquids and gases

“Good” and “bad” are subjective words – what seems “good” to one person may seem “bad” to another. Science works because it attempts to eliminate subjective opinions and to be as objective as possible (see post 16.22). So we need to be careful to avoid thinking about something as being “good” or “bad” and define… Continue reading 16.36 Good and Bad

Before you read this, I suggest you read posts 16.21 and 16.34. Suppose you blow air into a balloon until it is partly inflated. If you put the balloon somewhere warmer (at a higher temperature), it will inflate itself even more. When you put the balloon somewhere warmer, heat spontaneously flows into it (see post… Continue reading 16.35 Heat

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