Quick Notes

Quick Notes

Science Chapter 6: Heat
6.1 Temperature And Heat
 
Temperature is a physical quantity that indicates the internal energy of a body, object or environment in general. Heat is the exchange of thermal energy between two bodies that have different temperatures. Heat flows from high-temperature areas to low-temperature areas.
 
6.1  Temperature And Heat
 
  • Heat is a form of energy that is transferred because there is a difference in temperature
  • A material will become hotter when it receives heat, and will become colder when it loses heat
  • Heat cannot be seen but its presence can be felt.
  • Heat moves as energy waves, similar to other types of energy
  • Heat can change the state of a substance when the substance is heated or cooled
  • Heat can be released through chemical reaction. Heat is released together with other types of energy such as light.
 
Temperature
  • Temperature is a degree of measurement for hotness or coldness in a substance.
  • The temperature is measured using a thermometer.
  • The standard unit of temperature is degrees Celsius (symbol: ºC)
  • There are also other units of temperature measurement, namely degrees Fahrenheit (ºF) and degrees Kelvin (K).
 
Thermometer
  • The liquid in the thermometer will expand or shrink when exposed to different ambient temperatures
  • As the temperature of the substance decreases, the level of the liquid in the thermometer will decrease as the liquid shrinks
  • As the temperature of the substance increases, the level of the liquid in the realm of the thermometer will increase as the liquid expands
  • The correct techniques to measure temperature:
  1. Hold the thermometer upright at the upper stem. Do not hold the bulb because the heat from our body will affect the temperature reading.
  2. Immerse the bulb in the water. Do not let the bulb of the thermometer to touch the bottom or the sides of the container.
  3. When taking a reading, place your eyes at the same level of the meniscus of the liquid in the thermometer.
 
Expansion and contraction of matter
  • Matter is made of small particles called atoms. It exists as solids, liquids, and gases.
  • When a matter is heated, it gains heat.
  1. Heat energy causes the atoms to move faster.
  2. The atoms begin to move away from each other.
  3. As a result, the volume of matter increases, and the matter expands.

  • When a matter is cooled, the atoms in it loses heat energy.
  1. Atoms will move slowly and become closer to each other.
  2. As a result, the volume of matter decreases and the matter contracts.
 
Importance of application of expansion and contraction of matter
  • Mercury in the thermometer
  1. The mercury in the thermometer will expand when hot and will contract when cold
  2. This enables the temperature to be measured
  • Electric and telephone cables
  1. Cables are mounted loosely to prevent them from snapping when they contract in cold weather

  • Railway tracks
  1. Railway tracks are built with gaps between the tracks to allow expansion during hot weather
  2. The gaps prevent the railway tracks from bending

  • Concrete slabs on pavements
  1. Concrete slabs are arranged with gaps in between them to allow expansion during hot weather.
  2. This will prevent the concrete slabs from cracking.