Energy & Temperature Basics
Temperature is simply how hot or cold something is, measured in degrees Celsius (°C) or kelvin (K) using thermometers. When you heat water on the hob, you're transferring energy from the gas flame into the water's thermal store, making the water particles move faster and vibrate more.
The energy in thermal stores is measured in joules (J). This energy depends on how particles are arranged and how quickly they're moving about. Think of it like a busy playground - the more energetic the kids (particles), the more chaotic it becomes!
Heating can do three main things: increase temperature, cause changes of state (like melting ice), or trigger chemical reactions. Changes of state are physical changes - you're not creating new substances, just rearranging particles. That's why you can easily reverse them, unlike chemical changes such as burning, which permanently alter substances.
Quick Tip: Remember that physical changes are reversible (like melting chocolate), whilst chemical changes aren't (like burning toast)!