Temperature, Heat, and Expansion When matter gets warmer you are giving it energy. This makes the atoms or molecules in the matter move faster -If you get the atoms to move fast enough you can change from solid to liquid to gas.

Temperature Temperature is a number that tells you how hot or cold something is compared to a standard. The three major temperature scales; - Fahrenheit - Celsius - Kelvin

Fahrenheit Temperature Scale Used only in America. 32˚ is the temperature that water freezes 212˚ is the temperature that water boils

Celsius Temperature Scale Most widely used temperature scale 0˚ is the temperature that water freezes 100˚ is the temperature that water boils This is not an accident. This scale was designed around the freezing and boiling temperatures of water.

Kelvin Scale The temperature scale used in scientific research. Kelvin temperature measures the amount of energy in an object. Absolute Zero: zero degrees on the Kelvin scale. This is the coldest temperature possible. At this temperature (-273˚ C)the object has no energy.

Temperature and Kinetic Energy All temperature measurements tell the reader how much energy is in a sample. -If an object has a high temperature, the atoms in the object are moving quickly or have a lot of kinetic energy -If an object has a low temperature, the atoms in the object are moving slowly or have little kinetic energy

Heat Heat: the energy that transfers from one object to another because of a temperature difference Thermal Contact: When heat flows from one substance to another one it is in contact with -Heat always flows from the higher temperature substance to the lower temperature substance -This will continue to happen until the two objects are the same temperature

Thermal Equilibrium When objects that are in thermal contact with each other reach the same temperature. Internal Energy: the grand total of all energies inside a substance - When a substance takes in or gives off heat its internal energy changes.

Thermal Equilibrium If you pour two liquids that have different temperatures together what temperature will the mixture be? -It depends on the temperatures and amounts of each original liquid T f = M a T a + M b T b + … M a + M b + … T f means final temperature M means mass T means temperature a and b are the different original liquids

Measurement of Heat The amount of heat transferred can be determined by measuring the temperature change of a known mass of a substance that absorbs the heat. Calorie: the amount of heat required to raise the temperature of one gram of water 1˚ C - a kilocalorie is 1000 calories

Calculating Calories Q = mC∆T -Q means heat in calories, -m means mass, and -C means the specific heat capacity of a certain material, -∆T means change in temperature

Specific Heat Capacity The ability of a substance to store heat. -How much heat an object can hold depends on what it is made of Specific Heat: The amount of heat required to raise the temperature of 1 gram of a substance by 1˚ C

Calculating Specific Heat Capacity C = Q/m∆T - C means the specific heat capacity of a certain material, - Q means heat gained in calories, - m means mass, and - ∆T means change in temperature

Water’s Specific Heat Capacity Water has a very high specific heat = 4.18 J/g ˚C - This means that it takes a lot of energy to heat water up but when it get warm it takes a long time to cool down - Fall and early winter temperatures along the great lake shores

Thermal Expansion When the temperature of an object is increased, its molecules jiggle faster and normally that makes the atoms move farther apart. -This makes objects expand when they get warmer H:\Chemistry\Gas Laws\Copy of Can Crush Demo - Tank Car Crush Demo.htm

Bimetallic Strip Bimetallic Strip: two strips of different metals that are welded or riveted together. -The two different metals will expand at Different rates when expose to heat -This will make the strip bend when it is heated

Thermostat Thermostat: is used to measure the heat in a house and shut off a furnace when the house has reached a certain temperature. -A bimetallic strip in the thermostat will bend as The temperature in the house changes -When it expands to a certain point it will shut off a switch to the furnace

Expansion of Water Most liquids expand when they are heated. Water does not! -Water reduces its volume when it thaws from ice to liquid water -This happens because water will expand as it freezes

Ice is Less Dense than Liquid Water -Because water gets larger when it freezes it is less dense when solid than when it is a liquid. -This is why ice floats.

Can an entire freeze over from top to bottom? - Usually not. This is good for fish so that they can survive the winter. -For a body of water to freeze the entire body of water must be 4˚ C then ice can start forming on top. After that the ice forms from the top down.