the effects of heat on states of matter
TRANSCRIPT
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Grade 7 Term 3 Weeks 1-3
The effects of heat on states of matter
Temperature affects the change of state. The melting and boiling points are affected by impurities and
atmospheric pressure. The change from a liquid to a gas occurs at fixed temperatures for various substances.
The change from a solid to a liquid occurs at fixed temperatures which is specific for that substance.
Heating results in an increase in the movement and volume of matter. Gases expand the most when heated
while solids expand the least when heated. When solids are heated the energy of each particle is increased. It
vibrates more according to the amount of energy supplied so the particles are able to move. When liquids
are heated the energy of each particle is increased. The particles move more and further apart.
Figure 1: The effects of heat on states of matter
Inertia
Inertia is the tendency of a body to resist a change in
motion or rest. When a vehicle suddenly stops you
tend to jerk forward before coming to a complete
stop. In the same way you will jerk backwards when
the vehicle begins to move. This occurs because of
Newton’s first law of motion which states that ‘an
object at rest or motion will continue to be in this
state unless acted upon by an external force. In other
words, objects tend to “keep doing what they are
doing” unless disturbed. Figure 2: Newton’s First Law of Motion
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Diffusion of matter:
Particles move at random in liquids and gases. The movement of colours in a liquid is due to the movement
of particles in a liquid. Over time the random movement will result in the spreading out of particles from a
region where they are concentrated (more). This movement of particles from a region of high concentration
to a region of low concentration until they are evenly distributed is called diffusion. In other words,
diffusion occurs to spread particles equally across a given area/volume.
Diffusion takes place more quickly in a gaseous state than in a liquid state. This is because the particles in a
gas have more energy and move more quickly than the particles in a liquid.
The use of diffusion in maintaining life process include: gaseous exchange, absorption of digested food,
mixtures of liquids/ gases. The sense of smell depends on the diffusion of gas particles.
Examples of diffusion include: the smelling of perfume because it diffuses into the air and makes its way
into your nose, a teabag placed in a cup of hot water will diffuse into the water, cigarette smoke diffuses into
the air. The factors that influence the rate of diffusion are temperature and concentration. The rate of
diffusion is affected by increased: quantity, temperature, movement
NB: see worksheet for diffusion experiment to be done at home.
Activity:
A pot of soup is cooking on the
stove, which diagram indicates
when the lid of partially removed
and completely removed causing
diffusion to occur?
Figure 3: Rate of diffusion
A
B
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Air pressure
Air pressure is the weight of air molecules pressing down on the earth. The pressure of air molecules
changes as you move upwards from sea level into the atmosphere. Devices which make use of air pressure
are: the manometer and barometer.
A barometer is any instrument that measures air pressure. Barometers come in two basic forms: the aneroid
barometer and the mercury barometer. Aneroid barometers use cells that expand and contract as air pressure
changes. Air pressure is measured by attaching a needle into these cells. A mercury barometer, on the other
hand, uses mercury that rises and falls in response to air pressure changes.
Figure 4: An Aneroid barometer Figure 5: A Mercury barometer
A manometer is a device that measures air pressure using a
container with a "U"-shaped tube opened at one or both ends.
The height of the fluid on the open side will be higher on that
side when air pressure is less than the gas pressure and lower
on the open side when the air pressure exceeds the gas pressure
Figure 6: A manometer
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Worksheet: All questions should be answered in your Integrated Science notebook
1 a) Define the terms: expansion and compression
b) Explain why solids expand when heated
c) Describe what happens to the particles in water when it is heated
d) Have ever observed an adult using a pressure cooker? Give your understanding of how heat energy
causes gases to expand
2) a) Using a formula give the relationship between pressure and volume
b) Give the meaning for each variable in the formula given in 2(a)
3 a) What are TWO factors that influence diffusion?"
b) Explain how the rate of diffusion is affected any ONE of the factors named on 2 (a)
c) The following lab should be executed with care and caution and completed in your lab book
Title: Diffusion
Aim: To observe the process of diffusion in a liquid
Apparatus /Materials: Transparent glasses, water, drink mix, table spoon, and timer
Diagram: neatly drawn, labelled, title at the bottom in block letters
Before After
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Method: To be written in past tense
-Half fill a transparent glass with water
- Add one tablespoon of drink mix to the glass and immediately start the timer
-Record observations as soon the drink mix is added and then for every five minutes for 15
minutes.
-Gently stir the mixture after 15 minutes and record observations
Observations/Results:
Appropriate title above table in block letters
Time (minutes) Observations
0
5
10
15
After stirring
Discussion: What is diffusion? What caused the observation to change after every 5 minutes? Give one
example each for diffusion in air and liquid (other than what was mentioned in the handout)
Conclusion: what did you find out after conducting this experiment?
Reflection: What did you learn?
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Section 2 Notes
2.1 Pure Substances and Mixtures
All pure substances have their own unique set of properties, or characteristics All
mixtures contain two or more pure substances, which have their own distinct
properties (some of which may be hidden)
Homogenous Mixtures
- mixtures which look as though they have only one set of properties.
- the blended mixture has equal amounts of both substances (all parts of the
mixture are the same)
- if the homogenous mixture does not have any settling of any of the
substances it is made of, then it is called a solution
Matter
Mixtures
Mechanical
Mixtures
Solutions
Suspensions
& Colloids
Pure
Substances
- solutions occur because each particle slips between each other particle and
is evenly distributed throughout the entire mixture
Heterogeneous Mixtures
- the properties of the pure substances, in a heterogeneous mixture, are not
hidden
- if there are two or more materials that are visible within a mixture, then it
is called a heterogeneous mixture
In‐Between Mixtures
- a heterogeneous mixture, in which the particles settle slowly after mixing,
is called a suspension (eg. orange juice)
- a heterogeneous mixture, in which particles do not settle at all, is called a
colloid (eg. fog)
- mixtures that are obviously two or more substances are called mechanical
mixtures.
Paper Chromatography
A filter paper is placed partially in a solution – if the fluid moves up to only one
level it is a pure substance – if it moves up to multiple levels showing each
substance, then it is a solution.
The filter paper used in the paper chromatography test is called a chromatogram.
The distance a substance move up the chromatogram depends on its attraction to
the paper. Those with a stronger attraction to the paper don’t move up as far as
those with a weaker attraction.
Applications of Chromatography
Separation systems are used in a wide variety of industrial and scientific
applications. These systems isolate and analyze products that come from
mixtures formed during chemical synthesis. Chromatography applications are
used in many scientific analyses, including:
- Medical/biomedical research, quality control of pharmaceuticals, routine
clinical determination, and drug screening
- Space‐related and geo‐chemical research and development
- Forensic sciences
- Food and cosmetic chemical measurement
- Process control in the petroleum industry
- Environmental monitoring and pollution control
- Investigation of the chemistry and metabolism of biological systems.
2.2 Concentration and Solubility
Forming a solution by mixing two or more materials together is called dissolving.
Dissolving occurs because of the attracting between the particles (there may be a
stronger attraction to the particles of another substance, than to the particles of
the same substance).
Chromatogram Filter paper
Solvent
Ink spots
Solutes and Solvents
The solute is the substance that dissolves in a solvent. The solvent is the
substance that dissolves the solute to form a solution. Soluble means to be able
to be dissolved in a particular solvent. Solutes and solvents can be gases or
liquids.
Measuring Concentration
The concentration of a solution is the actual amount of solute in a specific
amount of solvent. example: 50 grams of solute dissolved in 100 ml of water has
a concentration of 50g/100ml (Another common way to express concentration is
how much solute is dissolved in a 100 ml of a solvent ). Concentration can also be
stated as a percentage ‐ ie. 5% (means, 5g/100ml). Extremely low concentrations
are stated in ppm (parts per million).
Comparing Concentrations
To compare concentrations of two solutions, you need to know the amount of
solute in the same volume of solvent for each solution.
Solution 1 10g of salt in 50ml of water
(10g/50ml)
= 20g/100ml
Solution 2 25g of salt in 100ml of water
(25g/100ml)
= 25g/100ml
Solution 2 has a higher concentration.
Saturated and Unsaturated Solutions
The limit to concentration is called solubility. (The maximum amount of solute
that can be dissolved in a fixed volume of solvent at a given temperature.)
• A saturated solution is one in which no more solute will dissolve in a
specific amount of solvent at a specific temperature ( Using the particle
theory, the attractive forces between the particles becomes balanced and
no more particles of the solute can be attracted by the particles of the
solvent )
• An unsaturated solution is one in which more solute can be dissolved in a
specific solvent at the same specific temperature
Supersaturated Solutions ‐ a solution that contains more solute than would
normally dissolve at a certain temperature is called a super‐saturated solution.
2.3 Factors Affecting Solubility
Water ‐ is called the 'universal solvent', because it can dissolve so many
materials. The term ’ aqueous ‘ means water.
97% of the water on Earth is Ocean water, 2% is frozen and only about 0.5% is
'usable' (and even this has materials already dissolved in it that can be harmful),
Solutions are not only made up of liquids. The chart on p. 29 illustrates other
mixtures that can make solutions.
Solubility Changes With Temperature
Solubility increases as the temperature of the solvent increases, because more
space is provided between the particles for the solute particles to fit (dissolve)
into. The reverse is true for a gas though ‐ as the temperature increases, the
solubility of a gas, in a liquid solvent decreases.
Thermal Pollution
This decrease in the solubility of gases can have a serious effect on the
environment. If the temperature of water increases (warm industrial waste water
poured directly into lakes and rivers) then there is less oxygen that can be
dissolved in the water – thus, affecting the living organisms in the water. This is
called thermal pollution.
2.4 The Particle Model of Matter and The Behaviour of Mixtures
1. All matter is made up of tiny particles. Different substances have different
particles.
2. The particles are always moving and vibrating.
3. The particles in matter may be attracted to each other or bonded together.
4. The particles have spaces between them
The particles flow in a fluid by moving freely past one another and at rest have a
flat surface. For this reason, solids do not flow, because at rest, they form a
coneshaped heap.
How The Particle Model Explains Mixing Substances
Particles are different sizes and when two substances are mixed, the smaller
particles fill the spaces between the larger particles. The particle model also
states that particles are attracted to each other. However, in some substances
particles can be attracted more to particles in other substances than to its own
particles.
Factors Affecting The Rate Of Dissolving
The speed at which the solute dissolves in a solvent is called the rate of dissolving
and can be affected by:
Temperature
Agitation ( stirring or shaking )
Size of pieces ( surface area exposed )
1. Select 20 equipment from the set above and state clearly what the equipment you choose
are used for in science. You will have to go to the internet to find the information. Write
the information in your science exercise book and paste the pictures there as well.
2. Use the formulae in the table to calculate the volumes of the shapes shown below.
