grade 7 science unit 2: heat

Grade 7 ScienceUnit 2: Heat Chapter 4: Temperature describes how hot or cold an object is.

Describing Temperature

How does temperature affect your daily life?

Why do you feel warm playing outside on a cold winter’s day?

TemperatureA description of how hot

or cold something is.

Activity

4-1A Boiling Hot, Freezing Cold p. 111

Standard Temperatures

Room Temperature – 22 oC

Body Temperature - 37 oCBoiling Point of Water - 100 oC

Freezing Point of Water - 0 oC

Air TemperatureRead p. 115 – 116

Reading Check p. 116 #1-3

Checkpoint

P. 119#6, 7, 8, 9

Measuring Temperature

Early Thermometers Galileo's Air

Thermometer▪ As the air heats, the liquids drops and rises when air is cooled.

Modern Day Galileo Thermometer

Early Thermometers

Early Liquid Thermometer: Liquid rising up the tube shows the temperature is rising.

Temperature ScalesScales are necessary for temperatures to be accurate and comparable.

3 commonly used scales are:1.Fahrenheit2.Celsius3.Kelvin

Fahrenheit Scale

Developed by Daniel Fahrenheit

The first to be widely usedFreezing of water occurs at 32 oF

Boiling of water occurs at 212 oF

Kelvin Scale

Developed by William Thomson (Lord Kelvin)

Scale states that the coldest temperature possible –absolute zero (-273 ˚C)

Celsius Scale

Developed by Anders Celsius Most commonly used temperature

scale Based on water freezing at 0 oC and

boiling at 100 oC .

Calibrating a Thermometer

To calibrate means to accurately assign a scale.

Steps to calibrating a Thermometer1.Place the bulb in a mixture of water

and ice.2.Mark the point at the top of the liquid

as 0 oC .3.Remove the bulb from the ice water

and place in boiling water. 4.Mark the point at the top of the liquid

as 100 oC 5.Divide the space between 0 and 100

into 100 even spaces. Each space will represent 1 oC .

Measuring Temperature Liquid in Glass Thermometer

The lab thermometer contains colored alcohol rather than mercury for safety.

Thermocouple

The Thermocouple Made of two wires of different metals. A temperature difference causes a

current to flow through the wires. This current is measured by a meter.

Can measure higher temperatures than typical thermometers.

The Resistance Thermometer (digital thermometers)

Bimetallic Strip (thermostat)

Made of two different metals fused together.

These metals expand and contract at different rates causing the strip to bend when heated.

Bimetallic Strip

Infrared Thermometer (thermogram)

Converts infrared radiation into colors that can interpret a temperature difference.

Checkpoint

P. 131#2, 3, 5, 6, 8, 12

P. 132 - 133#2, 10, 11, 15, 16, 18, 19