Presentation on theme: "HEATHEAT________ Heat is the transfer of thermal energy between objects. Heat always flows from warmer objects to cooler objects. Warm Thermal Energy Cool."— Presentation transcript:
HEATHEAT________ Heat is the transfer of thermal energy between objects. Heat always flows from warmer objects to cooler objects. Warm Thermal Energy Cool
Water Temperature 25 o C How Ice Cools Water Thermal Energy Water Temperature 21 o C Water Temperature 18 o C Water Temperature 15 o C Water Temperature 12 o C Water Temperature 10 o C
Temperature Temperature is the measure of how fast molecules of a substance are moving. The faster the molecules move, the higher the temperature. Even in solid objects, the molecules are moving, it’s just that they are vibrating in place.
Temperature Scales 212 100 32 0 The two temperature scales that are most commonly used are: Fahrenheit Celsius (Centigrade) Another scale, the Kelvin scale, is also used commonly in the scientific community. Water Freezes Water Boils FahrenheitCelsius
Temperature Scales Degrees Celcius, 0 00 0C, o oo on the Celcius scale water freezes at 0 0C and boils at 100 0C Degrees Farenheit, 0F on the Farenheit scale water freezes at 32 0F and boils at 212 0F Degrees Kelvin, 0K starts at absolute zero 0 0K, water freezes at 273 0K and boils at 373 0K
What is Absolute Zero? Absolute zero, 0 0 K,is the point where there is no molecular movement and therefore no thermal energy, no heat.Absolute zero, 0 0 K, is the point where there is no molecular movement and therefore no thermal energy, no heat. Absolute zero is a theoretical number.Absolute zero is a theoretical number. Since the molecules of all matter are moving, all matter has heat.Since the molecules of all matter are moving, all matter has heat.
Conductors are materials that allow heat to transfer easily. Conductors are usually made from materials that have atoms or molecules that are relatively close together. This allows the heat to “jump” from one molecule to the next. Materials such as metals are good conductors. HEAT
Insulators are materials that do not allow heat to transfer easily. Insulators are usually made from materials that have atoms or molecules that are relatively far apart. Materials such as plastic, rubber, wood, gases (air) are good insulators.
Heat Transfer As mentioned before, thermal energy always goes from the warmer object to the cooler object. This can happen in three ways: A) Conduction B) Convection C) Radiation
Conduction Conduction is the transfer of thermal energy through the direct contact of particles. One particles gains thermal energy and then transfers it to the particles closest to it. The closer the particles are to each other, the better the transfer of thermal energy.
Convection Convection is the transfer of thermal energy through the movement of fluids. As a fluid gets warmer, its density gets lower. As a result, the warmer fluid is pushed up and rises (hot air balloons work because of this principle). As it rises, it carries it thermal energy along with it, passing it to other particles as it travels. When it loses thermal energy, the density increases, causing it to sink and repeat the cycle once again.
Radiation Radiation is the transfer of thermal energy through the electromagnetic waves. Unlike conduction and convection, radiation does not need something (a medium) to transfer heat. The Sun, 93,000,000 miles from Earth, has no direct contact with Earth and nothing known flows between the Earth and the Sun. The only way the Earth can receive it’s energy from the Sun is radiation.
Thermal Expansion As an object gets warmer, its molecules move farther apart and the object expands. Also, the when an object cools, its molecules get closer together, and the object shrinks or contracts. IMPORTANT: Water is an exception to the contraction rule. As water cools, it contracts until it reaches 4 o C. Below 4 o C, water expands!
The shape of water molecules and their arrangement when they become solid causes water to expand as it freezes. Solid Liquid Gas