SCIE 4001
Unit 1
Introduction
About Matter
Nature of Matter
Properties of Matter
States of Matter
Kinetic Theory of Gases
 
 
 
Brownian Motion
 

Unit 1.1a Properties of Matter

Physical and Chemical Properties of Matter

Physical – characteristics we observe with our senses using very simple or no instruments/devices.

Colour & Texture of clean, unfinished (no paint etc.) surface

Smell

Attraction to magnets

Phase (state)

Melting point

Boiling point

Solubility in water and other substances

Density

Hardness

Flexibility

Strength

Absorbency

gold

Fig 1.1.37a.

Gold

Opacity: Opaque.

Colour: Yellow

Phase at 30°C: Solid

Density 19.3 g/ml

diamond

Fig 1.1.37b.

Diamond

Opacity: Transparent.

Colour: Colourless

Phase at 30°C: solid

Density 3.5 g/ml

water

Fig 1.1.37b.

Water

Opacity: Transparent.

Colour: Colourless

Phase at 30°C: solid

Density 1.0 g/ml

Every substance has its own set of characteristic physical properties that we can use to identify that substance.

Gold is an opaque, yellowish substance that is a solid at room temperature and has a density of 19300 kgm-3.

Diamond is a transparent substance that is a solid at room temperature and has a density of 3500 kgm-3.

Water is a transparent substance that is a liquid at room temperature and has a density of 1.0 kgm-3.

Chemical – characteristics we observe when reacting the substance with other “chemicals”.

particular reactions – when combined with other substances.

Observation of reaction and inferences from the products using physical properties:

— gases evolved

precipitated (insoluble products)

colour change in the reactants.

colour change in indicators like litmus.

Note that even if we are investigating chemical properties, we still have to resort to observation of some physical property to detect the change.

 

Main Points

1. Every substance has its own set of characteristic physical properties that we can use to identify that substance.

2. Physical – characteristics we observe with our senses using very simple or no instruments/devices. — Colour & Texture of clean, unfinished (no paint etc.) surface, Smell, Attraction to magnets, Phase (state), Melting point, Boiling point, Solubility in water and other substances, Density, Hardness, Flexibility, Strength and Absorbency

3. Chemical – characteristics we observe when reacting the substance with other “chemicals”. — particular reactions, when combined with other substances, observation of reaction and inferences from the products using physical properties, gases evolved, precipitated (insoluble products), colour change in the reactants, colour change in indicators like litmus

 

Questions:

1) How do these physical/chemical properties change with impurities?

2) Are physical properties definitive of materials? (can we be misled by our inferences from the observation of properties)? Explain.

3) What essential differences between melting and dissolving?

4) Are chemical properties definitive of materials? (or can we be misled by our inferences from the observations)? Explain.

5) What are some of the disadvantages of material identification based only on physical properties? Are there any advantages to using this as a method?

6) What are some of the disadvantages of material identification based only on chemical properties? Are there any advantages to using this as a method?

7) Explain how physical properties are important in chemical analysis.

8) What is the difference between hardness and strength?

9) What is the difference between mass and weight?

10) What is the difference between weight and density?

 

Activities:

Demonstrate that materials described as wood, stone, glass, plastic, metals etc. have certain sets of properties which help to identify them.

Observing physical changes of “pure materials” :

— Melting and boiling occur at a fixed temperature.

— Dew point and condensing of water vapour on the sides of a cold object.

— Formation of ice crystals on very cold objects like ice cream containers or 'dry' ice containers.

— Melting , boiling (safety!!!) and evaporation of substances which show these changes at temperatures easily obtained in classrooms.

— Water

— Candle wax / crayon

— Solid Carbon Dioxide (often called 'dry' ice)

— Napthelene (camphor balls)

— Buttter / lard / cooking oil

— Dissolving solids, liquids and gases in water and other common solvents.

— Difference between dissolving and melting.

— Comparing densities of different materials.

— Comparing flexibility of different materials.

— Comparing strength of different materials.

— Comparing absorbency of different materials.

— Comparing solubility of different materials.

— Observing attraction to magnets.

— Observing the colour of the clean, unfinished surface and inferring the nature of these materials.

 

Concept by Kishore Lal. Programmed by Kishore Lal... Copyright © 2015 Kishore Lal. All rights reserved.