Name _________________________________ Period _______ Date ____________ Heat (Thermal energy) Thermal energy is what we call energy that comes from heat. For example, a cup of hot tea has thermal energy in the form of kinetic energy from its particles. When you pour some milk into your tea, some of this energy is transferred to the particles in cold milk. What happens next? The cup of tea is cooler because it lost thermal energy to the milk. Heat and Thermal Energy Heat can do anything: move from one area to another, get atoms excited, and even increase energy. Did we say energy? That's what heat is. When you increase the heat in an area, you are really increasing the amount of energy in the area. Heat of Atoms Now all of this energy is moving around the world. You need to remember that it all happens on a really small scale. Energy that is transferred (moved) is at an atomic level. Atoms and molecules are giving and getting these tiny amounts of energy. When heat moves from one area to another, it's because millions of atoms and molecules are working together. Those millions of pieces become the flow or movement of energy throughout the entire planet. It’s kind of like you passing out candy and getting candy from any 6th grader. The candy spreads throughout the sixth grade because the students are giving and getting candy. Heat Movement Heat moves from one area to another because of differences in the temperatures of the area. If you have two areas with equal temperatures, there will be no flow of energy. But when you have two areas with different temperatures, the energy will start to flow. Areas of high temperature give off energy to areas with lower temperature. Think of standing in the door of a really hot room when the room behind you is cold. The air seems to create a breeze from the hot room to the cold room. This constant movement of heat from hot to cold is why there is energy throughout the universe. What is temperature? Temperature is the measure of the amount of heat specifically the measure of the movement of the molecules. The faster the molecules move the more the heat= greater temperature. Let's look at two examples to see the difference between heat and temperature. A swimming pool at 30°C is at a lower temperature than a cup of tea at 80°C. But the swimming pool contains more water, so it stores more thermal energy (more molecules moving) than the cup of tea. To boil water we must increase its temperature to 100°C. It takes longer to boil a large beaker of water than a small beaker because the large beaker contains more water and needs more thermal energy (molecule movement) to reach 100°C. What instrument is used to measure temperature? A thermometer containing either alcohol or mercury will most often be used in our science labs. There are some electronic and digital thermometers that you will sometimes find in the lab. What is the unit for temperature? Temperature is measured in units called degrees. Degrees are usually shown by a symbol that resembles a small zero placed slightly above and following a number. For example, thirty degree of temperature would be written as 30º. One of the most common units of temperature is the Fahrenheit degree, named after Gabriel Fahrenheit, who built thermometers over 250 years ago. Fahrenheit thermometers are commonly used in devices around the home like ovens and furnaces. Fahrenheit degrees are recorded by writing the number of degrees followed by the capital letter F (40º F). On this scale, the boiling point of water is 212º F, and the freezing point is 32º F. Another scale used on thermometers, like the ones most often used in science labs, is called the Celsius scale. It was devised (invented) by a Swedish astronomer named Anders Celsius. It is often called the centigrade scale, and the readings are followed by the capital letter C (83º C). Why do scientists use the Celsius scale instead of the Fahrenheit scale? Celsius is the metric unit of measure for temperature. The Celsius scale is based on water; 0º C is the freezing point of water, and 100º C is the boiling point of water. Questions: 1. A 3 liter bottle of water is placed in refrigerator, and heat is removed from the water. What happens to the movement of the molecules? 2. What is the scale for each line of the Celsius thermometer above? (Hint: it’s just like finding the scale on a graduated cylinder) 3. When you measure temperature what are you really measuring? (NOT HOW HOT OR COLD SOMETHING IS) SHOW ALL WORK! USE FORMULAS! 4. The largest ruby in the world is 10.9 cm long, 9.10 cm wide and 5.80 cm thick. If the ruby is 2284 grams, what it the ruby’s density? 5. Lithium is the lightest of metals and the least dense of all the nongaseous elements. A pure lithium sample with a volume of 13.0cm3 has a mass of 6.94 g. What is the density of lithium? Volume(mL) Mass (g) Density (g/ml)
5 3 6. Graph the data to the right on the graph below. Connect 10 6 the dots when finished. 15 9 7. Calculate the density of the object. Show work! 20 12 25 15 30
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8. Would the object sink or float in water? Why? 9. What do you notice about mass and volume? 20
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