- How does a thermometer work?
- Why does ice form on a body of water in winter?
- Why is the water at the bottom of a body of water colder than the water near the surface in the summer?
The thermal expansion of a liquid is used to measure the temperature
The classic liquid thermometer shows the temperature of air, liquids, or body temperature. It consists of a liquid in a narrow tube and a scale. The lower the temperature, the lower the liquid column falls. The higher the temperature, the higher the liquid column rises. Why is it like that? Liquids, as well as solids and gaseous substances, expand when heated. This is a phenomenon called thermal expansion.
The reading of the thermometer changes due to a property of substances called.
Temperature is measured in.
Bonus: When do we have to take thermal expansion into account?
Thermal expansion must be taken into account, for example, in the construction of railway tracks and bridges. Bridge beams and railway tracks are longer in summer than in winter because the temperature is higher. To allow them to expand, some space is left at their joints.
Think!
- Why do bridges swell in summer?
- Why are electric wires quite loose in summer and tight in winter?
What happens to boiling water in a pot?
If you want to boil water, always heat the water container from below. Why? As the warming water expands, it becomes less dense and therefore lighter — warm water rises in the pot, and colder and heavier water sinks. The water therefore circulates and heats evenly. If we tried to heat the water from above, it would not start circulating because the hot water would stay up. The water would still eventually heat up without circulating because it conducts heat, but it would take a very long time.
The water heated in a pot ...
- expands
- shrinks
- becomes lighter and less dense
- becomes heavier and more dense
- sinks
- rises
Water behaves differently from other liquids
Water behaves differently than most other substances when it warms and cools. When water is heated, it expands, and as water cools, it shrinks. But when it cools to 4°C and below (and starts to freeze), the water starts to expand instead of shrinking. That's why uninsulated water pipes can break in freezing weather when the water freezes and expands in the pipes.
The water's temperature was 10°C. The water cooled by 6°C. During cooling, the water. The same water cooled by another 4°C. This water.
Temperature differences in a body of water
When swimming during the summer, you must have felt that the water on the surface is always warmer than in the depths. That's the way it should be, because the cool water is denser and heavier and sinks to the bottom. The sun heats the surface of the body of water, but the warmed water does not mix with the cooler water below.
In winter, when the water cools down, the situation is different. The cooled water sinks to the bottom and pushes the warmer water upwards, where it, in turn, cools down. This circulation takes place until there is no water anywhere in the lake or pond warmer than 4°C. Then, the circulation of water stops, and only then can the surface temperature of the water drop to zero, and an ice cover begins to form on the surface.
I now know that…
Liquids, solids and gases expand when heated. Water shrinks when cooling until its temperature drops to 4°C, below which it starts to expand again. At the bottom of a body of water, the water is cooler in summer because the cool water is heavier and sinks to the bottom. In winter, the water at the bottom is warmer than on the surface.
