Year 10 Science Heat & Energy
Hot to cold
Thermal energy - Heat Heat is the energy stored in the motion of moving atoms. Molecules in a solid are fixed, but vibrate about an equilibrium position. The vibration is related to temperature. Molecules in a gas are free to move. The speed of the molecules is related to temperature.
Changes of state
Temperature Matter: Composed of molecules and atoms all continuously in motion. Temperature: A measure of this motion (thermal energy). The hotter the object, the higher its temperature, the faster the motion of the particles.
Temperature scales The three main temperature scales are: Celsius (C), Fahrenheit (F), Kelvin (K).
Fahrenheit scale Freezing point of water = 32 F Boiling point of water = 212 F Room temperature 20 C (68 F) Body temperature 37 C (98.6 F) 1 C is the same difference as 1.8 F
Celsius scale Freezing point of water = 0 degrees Boiling point of water = 100 degrees Coldest recorded -89 C (-129 F) in Antarctica. Warmest recorded 58 C (136 F) in Libya.
The Kelvin Temperature Scale Scientists most often use the Kelvin temperature scale (named after Lord Kelvin, a British scientist who studied heat). A change of one degree in the Kelvin scale is equal to a change of one degree in the Celsius scale. However the Kelvin scale starts at absolute zero. This is the temperature at which all particles stop moving. We also do not use the term degree, temperatures are just pronounced to be so many Kelvins.
Absolute zero Understanding the idea of absolute zero is a bit tricky! When some water turns to ice it does not look like it is moving. However the particles are still moving backwards and forwards but not very far. As we cool it down the particles move slower. When it gets very cold the particles move very slow. Eventually the particles stop moving, at this point they cannot move any slower – so we call this absolute zero.
The three scales
Water Temperature scale Melting point Boiling point Kelvin 273 373 Celsius 100 Fahrenheit 32 212
Some Interesting Temperatures -273°C Absolute Zero. -233°C The temperature of Pluto. -77°C Dry Ice evaporates. 0°C Ice melts. 37°C Average human temperature. 100°C Water boils. 1500°C Iron melts. 3000°C Temperature of a light bulb. 6000°C Temperature of the surface of the Sun. 20,000,000°C Temperature in the center of the Sun.
Cooling curves Aim: To investigate how quickly a thermometer cools down. Apparatus: Bunsen burner, heat proof mat, tripod, gauze, beaker, thermometer and timer.
Method: Heat a beaker of water to its boiling point. Place your thermometer into the beaker. When the temperature has reached 100C start the timer and remove the thermometer from the water. Record the temperature on the thermometer every 15 seconds for a total of five minutes. Analysis Draw a line graph with a smooth line of best fit.