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Natural sciences

Grade 8

Matter: classification

Module 16

Crystals and solutions

  • In the previous unit, mention was made of the formation of snowflakes.

Snow Crystals

  • Each snowflake is unique and is formed when drops of water vapour in the atmosphere condense as snow crystals.
  • Snow crystals develop six “arms” from a six-sided prism. Each “arm” grows differently as it is affected by continual minute temperature variations
  • Snow crystals combine to form snowflakes.
  • Some of the most valuable stones in the world consist of solid matter in the form of crystals.
  • Diamonds, rubies and sapphires are examples of precious stones. The atoms of these crystals form specific patterns.
  • Crystals have flat sides known as facets – they can take the form of triangles, rectangles, or many other shapes.
  • Minerals can be identified according to the crystalline form.
  • The basic form of crystals vary – salt, for instance, is cubical.
  • Most crystals have to be polished to reveal their beauty.

 Do you know the following? 

Sand is composed of quartz crystals. These crystals are shaped by constantly being knocked or rubbed against each other.

Read about QUARTZ WATCHES

Google.com (quartz +sand)

Rochhounding ar.com

Class Activity: Making a Solution

  • Fill a glass beaker with cold water.
  • Add a teaspoon of salt or sugar to the water and stir.
  • Continue stirring until the substance stops dissolving.

1. How many spoonfuls of the substance did you add?

  • Repeat the experiment with an equal amount of hot water.

2. What do you observe?

3. What deduction can be made?

4. Explain why warm water is more effective as a solvent:

  • Pour the solutes into watch-glasses and leave these on the classroom window sill for some days.

5. What do you observe after a few days?

6. What happened to the water?

  • Examine the crystals through a magnifying glass or a microscope.

Assignment: draw a couple of crystals to show their form.

Assessment for demonstration

Are you able to make correct deductions and communicate your findings?

[LO 1.3; LO 2.3]

Class project

Assignment:

Compile a scientific report on your investigation.

Grow your own crystals at home or in the classroom

You will need:

  • alum powder (obtainable from a chemist)
  • glass jars
  • cotton thread and a pair of scissors
  • a drinking straw
  • elastic band
  • Fill the jar with hot water.
  • Add alum powder by the method explained in the previous experiment – you will obtain a saturated solution. Use a watch-glass for crystals to form.
  • Use the cotton thread to attach the crystals to the drinking straw and suspend them in the jar to a depth of three-quarters down the jar.
  • Bend the straw and firmly attach it to the jar with the elastic band to hold it in position.

You will see crystals developing within a few days.

N.B.: Your educator could also let you grow copper sulphate crystals in the classroom.

Assessment of class project

Were you able to plan and execute the project, evaluate the data and apply your knowledge by handing in a properly compiled scientific report?

[LO 1.1; LO 1.2; LO 1.3; LO 2.4]

Problem Solving

Suppose you have a saturated solution, with excess crystals lying at the bottom of the beaker: Why would the crystals disappear if you began to heat the saturated solution slowly?

Assessment of problem solving

Were you able to provide an acceptable explanation for the problem?

[LO 2.4]

 Do you know the following? 

The gigantic rocks that form the Giant’s Causeway in Northern Ireland are hexagonal crystals that were formed when molten rock cooled down rapidly.

www.geocities.com/amegman_uk/symmetry.html

Assessment

Learning outcome 1: Scientific investigations

The learner will be able to act confidently on curiosity about natural phenomena, and to investigate relationships and solve problems in scientific, technological and environmental contexts.

ASSESSMENT STANDARD: We know this when the learner

1.1 is able to plan investigations;

1.2 is able to execute an investigation and collect data;

  • is able to evaluate data and communicate findings

Learning outcome 2: Constructing science knowledge

The learner will know and be able to interpret and apply scientific, technological and environmental knowledge.

ASSESSMENT STANDARD: We know this when the learner

2.3 is able to interpret information.

2.4 is able to apply knowledge.

Memorandum

CLASS ACTIVITY: MAKING SOLUTIONS

  • Warm water contains more energy and crystals dissolve much faster in this
  • Evaporation leads to crystallisation

ASSIGNMENT: CLASS PROJECT

  • The scientific report must include the following:

Purpose

Method

Materials

Results

Deduction

PROBLEM SOLVING:

  • The particles of warm water have more kinetic energy and are therefore further apart – more salt particles can fit into the spaces.

Questions & Answers

find the 15th term of the geometric sequince whose first is 18 and last term of 387
Jerwin Reply
I know this work
salma
The given of f(x=x-2. then what is the value of this f(3) 5f(x+1)
virgelyn Reply
hmm well what is the answer
Abhi
how do they get the third part x = (32)5/4
kinnecy Reply
can someone help me with some logarithmic and exponential equations.
Jeffrey Reply
sure. what is your question?
ninjadapaul
20/(×-6^2)
Salomon
okay, so you have 6 raised to the power of 2. what is that part of your answer
ninjadapaul
I don't understand what the A with approx sign and the boxed x mean
ninjadapaul
it think it's written 20/(X-6)^2 so it's 20 divided by X-6 squared
Salomon
I'm not sure why it wrote it the other way
Salomon
I got X =-6
Salomon
ok. so take the square root of both sides, now you have plus or minus the square root of 20= x-6
ninjadapaul
oops. ignore that.
ninjadapaul
so you not have an equal sign anywhere in the original equation?
ninjadapaul
hmm
Abhi
is it a question of log
Abhi
🤔.
Abhi
I rally confuse this number And equations too I need exactly help
salma
But this is not salma it's Faiza live in lousvile Ky I garbage this so I am going collage with JCTC that the of the collage thank you my friends
salma
Commplementary angles
Idrissa Reply
hello
Sherica
im all ears I need to learn
Sherica
right! what he said ⤴⤴⤴
Tamia
hii
Uday
hi
salma
what is a good calculator for all algebra; would a Casio fx 260 work with all algebra equations? please name the cheapest, thanks.
Kevin Reply
a perfect square v²+2v+_
Dearan Reply
kkk nice
Abdirahman Reply
algebra 2 Inequalities:If equation 2 = 0 it is an open set?
Kim Reply
or infinite solutions?
Kim
The answer is neither. The function, 2 = 0 cannot exist. Hence, the function is undefined.
Al
y=10×
Embra Reply
if |A| not equal to 0 and order of A is n prove that adj (adj A = |A|
Nancy Reply
rolling four fair dice and getting an even number an all four dice
ramon Reply
Kristine 2*2*2=8
Bridget Reply
Differences Between Laspeyres and Paasche Indices
Emedobi Reply
No. 7x -4y is simplified from 4x + (3y + 3x) -7y
Mary Reply
how do you translate this in Algebraic Expressions
linda Reply
Need to simplify the expresin. 3/7 (x+y)-1/7 (x-1)=
Crystal Reply
. After 3 months on a diet, Lisa had lost 12% of her original weight. She lost 21 pounds. What was Lisa's original weight?
Chris Reply
what's the easiest and fastest way to the synthesize AgNP?
Damian Reply
China
Cied
types of nano material
abeetha Reply
I start with an easy one. carbon nanotubes woven into a long filament like a string
Porter
many many of nanotubes
Porter
what is the k.e before it land
Yasmin
what is the function of carbon nanotubes?
Cesar
I'm interested in nanotube
Uday
what is nanomaterials​ and their applications of sensors.
Ramkumar Reply
what is nano technology
Sravani Reply
what is system testing?
AMJAD
preparation of nanomaterial
Victor Reply
Yes, Nanotechnology has a very fast field of applications and their is always something new to do with it...
Himanshu Reply
good afternoon madam
AMJAD
what is system testing
AMJAD
what is the application of nanotechnology?
Stotaw
In this morden time nanotechnology used in many field . 1-Electronics-manufacturad IC ,RAM,MRAM,solar panel etc 2-Helth and Medical-Nanomedicine,Drug Dilivery for cancer treatment etc 3- Atomobile -MEMS, Coating on car etc. and may other field for details you can check at Google
Azam
anybody can imagine what will be happen after 100 years from now in nano tech world
Prasenjit
after 100 year this will be not nanotechnology maybe this technology name will be change . maybe aftet 100 year . we work on electron lable practically about its properties and behaviour by the different instruments
Azam
name doesn't matter , whatever it will be change... I'm taking about effect on circumstances of the microscopic world
Prasenjit
how hard could it be to apply nanotechnology against viral infections such HIV or Ebola?
Damian
silver nanoparticles could handle the job?
Damian
not now but maybe in future only AgNP maybe any other nanomaterials
Azam
Hello
Uday
I'm interested in Nanotube
Uday
this technology will not going on for the long time , so I'm thinking about femtotechnology 10^-15
Prasenjit
can nanotechnology change the direction of the face of the world
Prasenjit Reply
At high concentrations (>0.01 M), the relation between absorptivity coefficient and absorbance is no longer linear. This is due to the electrostatic interactions between the quantum dots in close proximity. If the concentration of the solution is high, another effect that is seen is the scattering of light from the large number of quantum dots. This assumption only works at low concentrations of the analyte. Presence of stray light.
Ali Reply
the Beer law works very well for dilute solutions but fails for very high concentrations. why?
bamidele Reply
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
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Source:  OpenStax, Natural sciences grade 8. OpenStax CNX. Sep 12, 2009 Download for free at http://cnx.org/content/col11050/1.1
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