Lesson Notes By Weeks and Term - Senior Secondary School 1

SUBJECT: PHYSICS

CLASS:  SS 1

DATE:

TERM: 2nd TERM

REFERENCE BOOK

• New School Physics By M.W Anyakoha
• Senior Secondary School Physics By P.N Okeke

 
WEEK TWO

TOPIC: Thermometer and Its Type. Evaporation and Boiling

CONTENT

• Thermometer and Their Thermometric Substance

• Fixed Point of Thermometer 

• Evaporation and Boiling

Thermometer and Their Thermometric Substance

Thermometric substances are substances which changes in proportion to temperature.

ADVANTAGES OF MERCURY AS A THERMOMETRIC SUBSTANCE

1. Mercury does not wet glass
2. Mercury response quickly to slight change in temperature
3. The liquid does not vaporize easily
4. Mercury is opaque Hence, it can be seen easily
5. It has a regular or uniform expansion.

DISADVANTAGES

1. Mercury is expensive
2. Mercury can not be used to measure very low temperature because it’s freezing 

point  - 39˚C

ADVANTAGES OF ALCOHOL AS A THERMOMETRIC SUBSTANCE

1. Alcohol is less expensive than mercury
2.  It has larger expansion on heating than mercury (it expands 6 times more than 

mercury).

1. It can be used to measure very low temperature.

DISADVANTAGES

1. It is not opaque and so most be colored
2. It vaporizes easily
3. It wet glass
4. It has an irregular expansion
5. It has low boiling point of 78˚C

CONSTANT VOLUME GAS THERMOMETER

1. It gives more accurate measurement of temperature than any other 

thermometer

1. It is very sensitive and can measure wider range of temperature

DISADVANTAGES

1. It is very expensive and so require handling with special care
2. It is very cumbersome

EVALUATION

1. What advantage does a constant volume gas thermometer has over other 

thermometers?

1. Mention five types of thermometer, their thermometric substance and physical property.

FIXED POINT OF THERMOMETER

Fixed temperature  point are two reference temperature (usually upper and lower fix point) chosen, when preparing a scale for reading temperatures.

Upper Fixed Point: is the temperature of steam from pure water at the normal atmospheric pressure.

Lower Fixed Point: is the temperature of mixture of pure ice and water at normal pressure.

Fundamental Intervals: is the interval between the upper and lower fixed point.

      1000C                373K                          2120F       

    00C                273K                    320F

Celsius  Scale                      Kelvin  Scale            Farenheit Scale

REASON WHY WATER IS NOT USED AS A THERMOMETRIC

1. Water wet glass
2. They are colour less
3. It does not expand uniformly
4. It has small range of expansion (0˚C to 100˚C)

CLINICAL THERMOMETER

It is used for measuring the temperature of human body. The body temperature ranges from (35˚C to 45˚C). It is not advisable to sterilize a clinical thermometer in boiling water because a short range of 35˚C to 43˚C which shall result to 

1. Cracking or breaking of thermometer due to excessive expansion of the mercury.
2. Malfunction of the thermometer due to over expansion of the capillary tube and the mercury inside the bulb.

Evaporation and Boiling

Evaporation is the process where a liquid turns into vapor below its boiling point. Evaporation takes place at all temperature. Wind assist evaporation.

Boling is the change from liquid to vapor at the boiling point. It occurs throughout the entire volume of the liquid. Wind has no effect on boiling.

EVALUATION

1. Why is water not used as a thermometric substance?
2. Differentiate between evaporation and boiling.

Reading Assignment

www.google.com (click on google search, type “temperature & its measurement”, click on search) and New School Physics pg 202 - 209

WEEKEND ASSIGNMENT

1. The clinical thermometer is characterized by having a A.wide range of temperature B. wide bore  C. long stem  D. constriction
2. A short response time is obtained in a liquid - in-glass thermometer when the A. bulb is large and thick walled  B. bulb is small and thin walled C. stem is long and thin  D.bulb is thin walled and the liquid is a good conductor of heat.
3. Change in volume with temperature is the physical propety of ………. thermometer A. constant volume gas B. liquid-in-glass C. resistant 

1. thermoelectric

1. Convert  270C to kelvin A. 290K B. 300K C. 3000C D. 310K
2. The following are units of temperature except A. kelvin B. degree Celsius  

1. ampere D. Fahrenheit 

THEORY

1. Mention five types of thermometer, their thermometric substance and physical property.
2. Why is it not advisable to sterilize a clinical thermometer in boiling water?