Before you read this, I suggest you read posts 16.45 and 16.47. Why do we use soap to wash ourselves? Why don’t we just use water? If you’ve ever asked yourself these questions, you may have decided that using soap gets us cleaner. So why does soap get us cleaner? Not many people ask themselves… Continue reading 16.48 How does soap work?
The picture above shows how carbon, hydrogen and oxygen molecules combine to form a fat molecule; as expected each carbon atom forms 4 covalent bonds, each hydrogen atom forms 1 covalent bond and each oxygen atom forms 2 covalent bonds. (More information on covalent bonds and molecules is given in post 16.30.) The vertical bonds… Continue reading 16.47 Fats
Has anyone ever recommended something to cure a minor ailment, or something to improve your health, because “it worked for me”? This “something” could be an expensive commercial product (like some dietary supplements), aromatherapy, a copper bracelet, a magnetic bracelet, a change in diet or an exercise regime. The problem is that all of these… Continue reading 16.46 The placebo effect
Before you read this, I suggest you read posts 16.44, 16.30 and 16.27. The density of something is the mass of a sample of it divided by the volume of the sample (post 16.44). So, we might expect that, when we heat a solid, its density will increase; this is because when we heat a… Continue reading 16.45 Water
Which has the greatest mass 1 kg of steel or 1 kg of wood? (If you’re not sure what “mass” means see posts 16.12 and 16.13.) I hope that you immediately realised that both have the same mass of 1 kg. But we all believe that steel is “heavier” (it has a higher mass) than… Continue reading 16.44 Density
It would be useful to read posts 16.8 and 16.42 before you read this. Two previous posts (16.8 and 16.42) were about a biologist who developed a simple model to predict the number of rabbits on a farm. It took him 5 years to collect the data to develop his model. He then used it… Continue reading 16.43 Test before you predict
Before you read this, it would be useful to read post 16.8. Post 16.8 is a story about a biologist who investigated the rabbit population on a farm. He counted the number of rabbits every year for 5 years. When he plotted a graph of the number of rabbits against time, he got a straight… Continue reading 16.42 Keep it simple
“Physics World” is a magazine for members of the UK’s Institute of Physics. The September 2016 issue contained a very interesting letter about science teaching in schools, and especially about encouraging girls to study physics. However, the writer was concerned that many of her pupils can’t tell the difference between physics, chemistry and biology. They’re… Continue reading 16.41 Physics, chemistry and biology
Before you read this, I suggest that you read posts 16.27, 16.29, 16.30, 16.33 and 16.39. If you find this blog too difficult or tedious to read in detail, just notice that some complicated ions consist of several atoms covalently bonded, as in a molecule (see post 16.30), but with one or more extra electrons… Continue reading 16.40 Complicated ions
Before you read this, I suggest that you read posts 16.25, 16.27, 16.29 and 16.37 In a previous post, we have seen how atoms of different elements can combine to form compounds (post 16.30). So far we have considered only one type of compound, in which atoms of different elements are joined together to make… Continue reading 16.39 Ions
