This experiment is investigating how temperature affects the rate of dissolving.
The temperature of the water in each beaker should also be measured and recorded.
The factors that should be kept constant are the amount of water and vitamin C tablet used. The variable factor is the temperature of the water.
Two other factors that affect the rate of dissolving are the size of particles and stirring/agitation.
A mixture forms when two or more substances are combined such that each substance retains its own chemical identity. Everywhere around us are made up of mixtures. We can see them in nature, along the surface of the earth, in the oceans and in the foods we eat. There are infinite numbers of mixtures that can be combined into homogeneous or heterogeneous.
Heterogeneous and Homogeneous Mixtures are discussed in this presentation. High School chemistry, physical science, environmental science, earth systems, and material science students will benefit from this presentation. All essential introductory concepts are presented here.
A mixture forms when two or more substances are combined such that each substance retains its own chemical identity. Everywhere around us are made up of mixtures. We can see them in nature, along the surface of the earth, in the oceans and in the foods we eat. There are infinite numbers of mixtures that can be combined into homogeneous or heterogeneous.
Heterogeneous and Homogeneous Mixtures are discussed in this presentation. High School chemistry, physical science, environmental science, earth systems, and material science students will benefit from this presentation. All essential introductory concepts are presented here.
DISSOLUTION
Dissolution is defined as a process in which a solid substance solubilises in a given solvent.
(i.e. mass transfer from the solid surface to the liquid phase.)
Three Theories:
Diffusion layer model / Film theory
Danckwert’s model / Penetration or Surface renewal theory
Interfacial barrier model / Double barrier or Limited solvation theory
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Dear Dr. Kornbluth and Mr. Gorenberg,
The US House of Representatives is deeply concerned by ongoing and pervasive acts of antisemitic
harassment and intimidation at the Massachusetts Institute of Technology (MIT). Failing to act decisively to ensure a safe learning environment for all students would be a grave dereliction of your responsibilities as President of MIT and Chair of the MIT Corporation.
This Congress will not stand idly by and allow an environment hostile to Jewish students to persist. The House believes that your institution is in violation of Title VI of the Civil Rights Act, and the inability or
unwillingness to rectify this violation through action requires accountability.
Postsecondary education is a unique opportunity for students to learn and have their ideas and beliefs challenged. However, universities receiving hundreds of millions of federal funds annually have denied
students that opportunity and have been hijacked to become venues for the promotion of terrorism, antisemitic harassment and intimidation, unlawful encampments, and in some cases, assaults and riots.
The House of Representatives will not countenance the use of federal funds to indoctrinate students into hateful, antisemitic, anti-American supporters of terrorism. Investigations into campus antisemitism by the Committee on Education and the Workforce and the Committee on Ways and Means have been expanded into a Congress-wide probe across all relevant jurisdictions to address this national crisis. The undersigned Committees will conduct oversight into the use of federal funds at MIT and its learning environment under authorities granted to each Committee.
• The Committee on Education and the Workforce has been investigating your institution since December 7, 2023. The Committee has broad jurisdiction over postsecondary education, including its compliance with Title VI of the Civil Rights Act, campus safety concerns over disruptions to the learning environment, and the awarding of federal student aid under the Higher Education Act.
• The Committee on Oversight and Accountability is investigating the sources of funding and other support flowing to groups espousing pro-Hamas propaganda and engaged in antisemitic harassment and intimidation of students. The Committee on Oversight and Accountability is the principal oversight committee of the US House of Representatives and has broad authority to investigate “any matter” at “any time” under House Rule X.
• The Committee on Ways and Means has been investigating several universities since November 15, 2023, when the Committee held a hearing entitled From Ivory Towers to Dark Corners: Investigating the Nexus Between Antisemitism, Tax-Exempt Universities, and Terror Financing. The Committee followed the hearing with letters to those institutions on January 10, 202
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Synthetic fiber production is a fascinating and complex field that blends chemistry, engineering, and environmental science. By understanding these aspects, students can gain a comprehensive view of synthetic fiber production, its impact on society and the environment, and the potential for future innovations. Synthetic fibers play a crucial role in modern society, impacting various aspects of daily life, industry, and the environment. ynthetic fibers are integral to modern life, offering a range of benefits from cost-effectiveness and versatility to innovative applications and performance characteristics. While they pose environmental challenges, ongoing research and development aim to create more sustainable and eco-friendly alternatives. Understanding the importance of synthetic fibers helps in appreciating their role in the economy, industry, and daily life, while also emphasizing the need for sustainable practices and innovation.
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Operation “Blue Star” is the only event in the history of Independent India where the state went into war with its own people. Even after about 40 years it is not clear if it was culmination of states anger over people of the region, a political game of power or start of dictatorial chapter in the democratic setup.
The people of Punjab felt alienated from main stream due to denial of their just demands during a long democratic struggle since independence. As it happen all over the word, it led to militant struggle with great loss of lives of military, police and civilian personnel. Killing of Indira Gandhi and massacre of innocent Sikhs in Delhi and other India cities was also associated with this movement.
The French Revolution, which began in 1789, was a period of radical social and political upheaval in France. It marked the decline of absolute monarchies, the rise of secular and democratic republics, and the eventual rise of Napoleon Bonaparte. This revolutionary period is crucial in understanding the transition from feudalism to modernity in Europe.
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2. Lesson Objectives
By the end of the lessons students sbat
•distinguish among solute solvent, solution
•deduce the nature of solutions and
suspensions by simple laboratory tests
•state the factors affecting solubility
•state the factors affecting rate of dissolving
•distinguish between a solution and a
suspension
3. Quick Recap
• Matter can be
classified as
elements, compounds
and mixtures.
• Element
– An element is a
substance that cannot
be broken down into
simpler substances.
– Examples: carbon, gold,
iron, oxygen
4. Quick Recap
• Compound
– A compound is a
substance made up of
2 or more elements
chemically combined
together.
– A compound is a
substance that can be
broken down into
simpler substances by
chemical methods.
– Examples: water, carbon
dioxide, ethanol
5. Quick Recap
• Mixture
– A mixture is a substance made up of 2 or more
elements and/or compounds not chemically
combined together.
– A mixture is a substance that can be broken down
into simpler substances by physical methods
– Examples: air, seawater, crude oil, steel
6. Quick Recap
A mixture can further be classified as a solution. or a suspension
Matter
Pure substances
Elements
Compounds
Mixtures
Solutions
Suspensions
7. Solutions
• When salt is added into water, salt
dissolves in water.
– Salt is known as the solute (substance that
dissolves in the solvent).
– Water is known as the solvent (substance that
dissolves the solute).
– The final mixture is known as the solution.
9. Wake Up Call 1
substance 1
solute or substance solute or
solvent?
2
example
solvent?
a
carbon dioxide
water
aerated drinks
b
water
salt
saline solution
c
alcohol
iodine
tincture of iodine
solution
b
dishwashing
detergent
oil
washing dishes
10. Suspensions
• When a solid does not dissolve
in a liquid, a suspension is
formed.
• A suspension is a mixture in
which insoluble particles are
suspended in a liquid or a gas.
11. Comparing solutions and
suspensions
1
2
3
Solutions
Homogeneous
(Colour, density of the
solution is the same.)
When left to stand, solute
does not separate from
solvent.
Suspensions
Heterogeneous
When left to stand, the
insoluble particles will
sink to the bottom of the
container.
When filtered, no residue is When filtered, the
left on the filter paper.
insoluble particles are left
as residue on the filter
paper
12. Wake Up Call 2
Mixture
Solution or
suspension?
a.
mud
b.
honey (a mixture of different sugars)
c.
flour in water
d.
paint
e.
some medicines that require shaking before
use (e.g. paracetamol mixture)
f.
perfumes (oils in alcohol)
13. Solubility
• Salt dissolves easily in water.
– However there is a limit to how much salt can
dissolve in water.
– This limit depends on the solubility of the
solute.
Solubility is the maximum amount of solute
that can dissolve in 100 g of solvent at a
given temperature.
14. Factors affecting solubility
Factor
1. Nature of
solvent
2. Nature of
solute
3. Temperature
Explanation
iodine dissolves better in alcohol than in
water. Hence, iodine has higher solubility
in alcohol than in water.
Different solutes have different
solubility in the same solvent. E.g. salt
dissolves in water better than baking
soda does.
More substance can dissolve in the
same amount of solvent at a higher
temperature. E.g. coffee dissolves
15. Rate of dissolving
Think!
•To make a cup of tea, a teabag is placed in
a cup of water. Sugar is then added. How
can sugar be made to dissolve faster?
16. Rate of dissolving
1. Use hot water / heat up the tea
2. Stir the tea
3. Use sugar crystals instead of large
lumps of sugar.
The rate of dissolving is the speed at
which the solute dissolves in a fixed
amount of water.
17. Rate of dissolving
• What are the factors that affect the how
fast a solute dissolves (rate of dissolving)?
Factor
How rate of dissolving is affected
1
Temperature
The higher the temperature, the faster the
solute dissolves. (i.e. rate of dissolving
increases with higher temperature)
2
Rate of
stirring
The faster the mixture is stirred, the faster the
solute dissolves.
3
Size of
particles
The smaller the solute particles, the faster the
solute dissolves. (E.g. 10 g of powdered
sugar dissolves faster than 10 g of rock
sugar.)
18. Particle size
• For a cube of dimension 2 cm by 2 cm by
2 cm, its total surface area would be:
2 cm
Total surface area = 2 x 2 x 6cm
= 24 cm2
19. Particle size
• If the 2 x 2 x 2 cube was cut into 1 x 1 x 1
cubes,
cut
1 cm
X 8 cubes
20. Particle size
1 cm
X 8 cubes
Total surface area = [1 x 1 x 6] x 8
= 48 cm2
What can you conclude from this?
•When the particles are smaller,
for the same mass of substance,
there is higher total surface area
coming into contact with the
solvent, therefore smaller particles
dissolve faster.
21. Wake Up Call 2
• Vitamin C tablets are very soluble in water.
22. Wake Up Call 2
• An experiment was conducted to find out how
ONE factor affects the rate of dissolving.
• Procedure:
– Place some distilled water into a beaker. Label the
beaker A.
– Place some warm distilled water into another beaker.
Label the beaker B.
– To each beaker, add one Vit C tablet.
– Measure & record the time taken for the table to
completely dissolve.
23. Wake Up Call 2
1. What is this experiment investigating?
2. Other than the time taken for the tablet to completely
dissolve, state another reading that should be taken.
3. What factors in this experiment should be kept
constant? What is the variable factor?
4. State two other factors that affect the rate of dissolving.