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 * =Unit 2:Heat Chapter 1 Temperature=
 * =Unit 2:Heat Chapter 1 Temperature=

Temperature describes how hot or cold an object is.

We can sense changes in temperature with our sight, touch and smell. For example: we see ice melting, feel a hot drink on our tongue or smell things cooking on the stove. Knowing the temperature in things is important to every day life and we can measure temperatures changes with modern instruments.


 * Common Temperatures**


 * Room temperature:** One of the many common temperatures is room temperature which is somewhere between 20c and 23c and what most people choose their room temperature to be.


 * Cooking/Food Temperature:** The correct temperature for cooking and storing food is important. A meat thermometer helps you cook meat properly. Thermometers in stoves and ovens are used to set the temperature to cook food. A good temperature for baking your cookies (if you like cookies) would be a temperature of 175c . If you have a refrigerator the temperature should be 4c and your freezer should have a temperature of -18c to make sure food kept there does not spoil.




 * Body Temperature**: Knowing if a person's temperature is too low or to high can help find out if a person is sick. The body temperature of a healthy human is 37c and if you get hypothermia your body temperature starts to drop to 32c. However if your temperature starts to rise to 40c or higher it can really affect your tissues especially your brain.The normal body temperatures of animals are different than humans. Some animal temperatures are: a dog has body temperature of 38.5c, and a pig has a temperature of 39.5c, and a hedgehog has a temperature of 34.0c.


 * Air Temperatures:** Measuring the temperature outside helps us to decide what wear outdoors and if we need the heat on inside. In July in northern Labrador the degrees probably be 5c to 10c and the more you go south the degrees starts to rise by 5c. In January if you are in the North, North West and Western the degrees will most likely be -20c to -25c and the more you go south-east temperature will start to rise.




 * Instruments to Measure Temperature**


 * Thermoscope**:

One of the first instruments to measure temperature was invented by Galileo Galilei in 1596 made of a glass bulb with a long narrow tube and a container filled with a colored liquid. As the bulb is cooled or warmed the liquid moves and shows a change in temperature, but not how much change. This instrument did not have numbers to show how hot or cold.




 * //The Fahrenheit Scale://**

//The Fahrenheit scale was invented by Gabriel Fahrenheit (1686-1736). Other scientists were using liquid like alcohol and mercury in their thermometers to show changes in temperature as the liquids expand and contract. Fahrenheit used many experiments to improve these thermometers. His thermometer used mercury and assigned numbers to the scale of his thermometer to measure temperatures. Fahrenheit chose the coldest temperature to be made in a lab, which was a mixture of salt, ice and water. The temperature was called absolute zero which is also known as -273.15c. He found body temperature would be close to 100 on the Fahrenheit scale and divided the space between 0 and 100 into units and called them degrees. The freezing point of water is 32 degrees F and he boiling point of water is 212 degrees F, and body temperature is now known to be 98.6 degrees F. The Fahrenheit scale was the first to be widely used by scientists.//


 * //The Celsius scale://**

//The Celsius scale is the most commonly used today. On a different place on the earth a Swedish astronomer named Anders Celsius (1701-1744) made a different scale. He showed the freezing and boiling point of water are always the same if they are measured under the same conditions and used the atmospheric pressure at sea level as his standards for the scale. On the Celsius scale the freezing point of water is 0c and the boiling point is 100c.//




 * Kelvin Scale:**

In the 1800s William Thomson ,who was known as lord kelvin was studying temperature change on gases.The lowest temperature on the kelvin scale was called absolute zero and had units the same size as the Celsius scale. The units are called kelvins and symbolized with a capital K.


 * //Calibrating a thermometer// **

//To calibrate a thermometer or any thing related to a thermometer like a thermocouple means to assign numbers on a kind of scale. A good method for calibrating your thermometer is to put the end of your thermometer in a mixture of water and ice, look at the alcohol/mercury until it doesn't move. Draw the point where the mercury/alcohol and label it 0c. Take the thermometer from the cold ice water and put it in some boiling water, let the mercury/alcohol rise for awhile until it stops moving. Then draw the point where the liquid is right now and then write down 100c. Divide each space between the two degrees into a 100 equal spaces and each space represents 1 degree.//


 * //Bimetallic strip://**

//They were invented to measure temperature more accurately. Bimetallic strips are used in heaters and furnaces to turn them on and off. A bimetallic strip is made up of two metals that will expand at two different amounts when heated. In thermostats the strip is made into a coil when heated will tighten and when cooled will uncoil and turns the furnace or heater on and off.//




 * The Thermocouple:**

Thermocouples are more durable and can measure higher temperatures then other instruments. A thermocouple is made up of different metals connected at both ends. There is a difference between the two ends where the metal connect and causes an electric current to flow through the wires. The amount of current flowing in the wires is measured and indicates the temperature.




 * Infrared Thermograms:**

Thermograms are used to measure the amount of infrared radiation given off by objects around us that we cant see with our eyes. Film and electronic devices sense the radiation and convert into colors that are interpreted temperature differences. Thermal imaging is used in surveillance by the military, by contractors to find where heat is being lost from buildings, and by firefighters for looking for people who might be inside buildings.

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