TEMPERATURE

DEFINITION•Degree of hotness and coldness of a body

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QUESTIONS:1.How can we simplify the definition of

temperature?2.Is heat different from temperature? Why?

HEAT VS. TEMPERATURE• The temperature of an object tells us how HOT it is

•Measured in degrees Celsius - °C

• It is NOT the same as heat energy although the two quantities are related.

HEAT AND TEMPERATURE ARE RELATED BECAUSE…

• If an object has become hotter, it means that it has gained heat energy.

• If an object cools down, it means it has lost energy.

HEATDefinitions, Concepts and its Measurement

OBJECTIVES•Define heat, specific heat, heat capacity and water equivalent•Differentiate heat from temperature• Solve problems involving heat

WHAT IS HEAT?• It is a form of energy that is transferred from one body to another due to a difference in temperature.

• Its SI unit is Joule (J)

• Its common unit is caloriePlay

WHAT IS CALORIE?• Amount of heat needed to change the temperature of 1g of water

• 1 calorie (water) = 4.186J

WHAT ARE THE EFFECTS OF HEAT?• Change in phase• Change in size• Chemical change• Rise in temperature SPECIFIC HEAT and

HEAT CAPACITY

WHAT IS SPECIFIC HEAT?

• It is the amount of heat needed to change the temperature of the unit mass of a substance by 1 degree.

• Its SI unit is Joule/ kg°C (J / kg°C )

• The heat capacity of a substance per unit mass

• Its symbol is small letter “c” .

FORMULA

𝑐=𝐻

𝑚∆𝑇Specific

Heat

Heat Absorbed

or Given off

Mass Change in Temperature

SAMPLE PROBLEM:The specific heat of aluminium is 900J/kg°C. How much heat is needed to change the temperature of 2kg object made of aluminium from 25°C to 35°C? How much will the temperature change if 10,000 J of heat are removed from it?

HEATUsing ,

H= 18,000 J

CHANGE IN TEMPERATURE

H= -10,000 JUsing , = -5.6°C

Meaning, the object is cooled.

HEAT CAPACITY•Amount of heat needed to change the temperature of a given mass of the substance by 1 degree.• Its SI unit is J/°C• ratio of the amount of energy absorbed to the associated temperature rise.

• Its symbol is capital letter “C”

FORMULAC = m*cHeat

Capacity Specific Heat

Mass

WATER EQUIVALENT•Mass of water that has the same heat capacity of the object.•The SI unit is kg

•

SAMPLE PROBLEM:The addition of 64,500 J of heat raises the temperature of a 5kg object from 25.5 °C to 43.5 °C. Determine its specific heat, heat capacity, water equivalent and mass of copper (390 J/kg °C) having the same water equivalent.

SPECIFIC HEAT717 J/kg °C

HEAT CAPACITY3585 J/ °C

WATER EQUIVALENT0.86 kg

MASS OF THE COPPER9.19kg

SYNTHESIS•What is heat?•How is heat differ from temperature?•What are the effects of heat?•Differentiate specific heat from heat capacity.•What is water equivalent?

OBJECTIVES•Define heat, specific heat, heat capacity and water equivalent•Differentiate heat from temperature• Solve problems involving heat

PRACTICE EXERCISE1. How much heat is needed to change the temperature

of a 2kg block of copper from 10 °C to 140 °C?

2. The temperature of a 5kg object raises from 25.5 °C to 43.5 °C. If 85,350 J of heat is added, determine its specific heat, heat capacity, water equivalent and mass of aluminum (900 J/kg °C) having the same water equivalent.

“Temperature is a property of an object, heat is a property of

change”.

REFLECTIONRefer to this statement, “Temperature is a property of an object, heat is a property of change”. Give several everyday examples and try to relate this idea in your own words.