Marble run: Techxploration on Gravitational energy

The structure we used:

Describe how you slowed the speed of the marble.
We slowed down the speed of the marble by enforcing the turning points of the straw with tape, increasing friction between the marble and the track. We also placed small plasticine speed bumps
along the track.

How long did your marble take to roll to the bottom of your design?
13s

What was your most difficult problem you had solving this Challenge?
Having the marble roll smoothly down the track without stopping.

What parts of your design pleased you most?
The plasticine bumps. They served to increase friction between the marble and the track and also to slow the marble down further.

How might your design be improved?
It might be improved by lowering the gradient at which the board was tilted or increase the friction between the track and the marble so as to slow the marble down even more.

Can you think of three types of guiding structures? Draw them and write short descriptions.

Give three examples of other kinds of kinetic energy. Make drawings and write descriptions.

Describe gravitational energy in your own words; how it works, why it is important, and what would happen if there wasn't any gravity on earth.
Gravitational energy is the energy that draws a smaller object towards a larger object of greater mass. Objects with a greater mass have stronger attractive forces than smaller objects, this attractive force is called gravity. If there wasn't any gravity on Earth, everything will be floating around.

Lab session 7

Reactions with Alkali

Today, a continuation from last week, we did experiments to investigate the properties of alkali.

Properties of Bases

ACTIVITY #1

1. Place a piece of blue litmus paper, red litmus paper and a drop of universal indicator on a white tile.

2. Carefully add a drop of dilute sodium hydroxide to all three indicators.
3. Repeat steps 1 & 2 with dilute potassium hydroxide and ammonia water.

Results:

Observations:
-Bases turn Red litmus paper blue and blue litmus paper blue.
-Bases have a pH of near 7 to 14.0

ACTIVITY#2

1. Carefully add dilute sodium hydroxide into a test tube up to 2cm in height.
2. Light the Bunsen burner.
3. Carefully add 1 spatula of ammonium chloride to the test tube.
4. Warm the test tube gently over a Bunsen flame:

5. Moisten a piece of red litmus paper and place it at the mouth of the test tube.
6. Gently fan some gas towards your nose.

Results:

Observations:
-Effervescence observed, colorless and pungent gas evolved.
-The gas evolved turned the red litmus paper blue

ACTIVITY #3

1. Using a clean boiling tube, add dilute hydrochloric acid up to 2cm in height.
2. Add 3 drops of universal indicator to the boiling tube:

3. Using a dropper, add 1cm of dilute sodium hydroxide to the acidic the boiling tube and gently shake the boiling tube:

(Starts turning blue-ish. It turned violet but it changed color too fast):

(To yellow)

This is a neutralization process. 

Lab session 6

Part 2

The properties of acids

ACTIVITY 1

1. Place a piece of blue litmus paper, red litmus paper and universal indicator on a white tile. 

2. Use the dropper to carefully add a drop of dilute sulfuric acid to all three strips of indicator. 

Results: 

-Blue litmus paper turns red

-Red litmus paper turns red

-Universal indicator turns red (pH 4.0): 

Conclusion: Acids turn Blue litmus paper red and Red litmus paper red. Acids change the color of the universal indicator. The pH range of acids is <7. 

ACTIVITY 2

1. Using a clean test tube, add dilute hydrochloric acid to the test tube up to 2cm in height. 

2. Light the Bunsen burner.

3. Carefully slip one piece of magnesium ribbon into the test tube. 

Observations: The magnesium ribbon dissolves and the test tube feels hot to the touch.

4. Using a wooden splint, light it using the Bunsen flame and place it at the mouth of the test tube. 

Observations: When the wooden splint was placed in the test tube, a "pop" sound was produced. 

ACTIVITY 3

1. Using a clean boiling tube, add dilute hydrochloric acid to the test tube up to 2cm in height. 

2. Pour calcium carbonate into another test tube up to 2cm in height. 

2. Prepare a set up according to the diagram:

3. Add a spatula of sodium carbonate to the acid in he boiling tube. 

4. Fix the rubber stopper of the delivery tube on the mouth of the boiling tube and place the other end into the test tube containing calcium carbonate.

Observations: A white precipitate is formed and the calcium carbonate (limewater) turns cloudy. 

Lab session 6

Part 1 

Chemical Changes due to light

Procedure:

1. Select a clean, opaque object to be used for this experiment.

2. Place a piece of filter paper on a petri dish. Soak the filter paper with sodium chloride solution:

3. Remove the filter paper and place it on a clean white tile. 

4. Carefully drip silver nitrate solution on the paper.

You will observe white precipitate (Silver chloride) being formed on the filter paper:

(Silver chloride + Sodium nitrate)

5. Place the opaque object on top of the filter paper. (We did not have time to do it with the opaque object, so we just did without it.)

6. Place the paper in bright light for 15-20 minutes

Results: Where the white precipitate formed, there was a purple colored patch. This is decomposed silver. The silver chloride formed in in the white precipitate decomposed under light to form silver metal. 

Thermal decomposition

Procedure: 

1. Add a level spatula of the copper (II) nitrate solid in a test tube

2. Gently heat the solid in the test tube over a Bunsen flame: 

Here's multiple pictures to show the change over time:

Results: As can be observed, the copper (II) nitrate became darker, decomposing to form a black solid copper (II) oxide. Although it cannot be seen from the pictures above, effervescence was observed during the experiment, where oxygen and nitrogen dioxide were formed.

Copper (II) nitrate (s) --> Copper (II) oxide (s) + Oxygen (g) + Nitrogen dioxide (g)

Precipitation 

1. Add 10cm^3 of aqueous copper (II) nitrate into a test tube.

2. Add 4 drops of aqueous sodium hydroxide into the test tube.

A blue precipitate is observed:

                        

Results: A blue precipitate (Copper (II) hydroxide + sodium nitrate) is formed and remains after the reaction.

Copper (II) nitrate (l) + odium hydroxide (l) --> Copper (II) hydroxide + sodium nitrate

1.  Fill a boiling tube with potassium iodide solution to about 1cm in height.

2. Add 5 drops of lead (II) nitrate solution to the boiling tube. 

A yellow precipitate is formed:

(Potassium nitrate + lead (II) iodide)

3. Add water to the boiling tube until it is half full. 

4. Heat the resulting mixture to obtain a near colorless solution. 

5. Allow boiling tube to cool on a test tube rack for approximately 10 minutes.

Results: The yellow precipitate dissolved to form a colorless solution during heating and yellow crystals were formed upon cooling. 

Potassium iodide (l) + lead (II) nitrate (l) --> Potassium nitrate + lead (II) iodide

Combustion

1. In a beaker of soap water, bubble gas (propane gas) from the gas tap into the soap water. 

2. Light a lighter at the bubbles.

Results: Flames are observed. The water and colorless gas remains. 

Propane (g) --> oxygen (g) + water (l)

Lab session 5

In this lab session, we explored various changes, namely CHEMICAL and PHYSICAL changes in elements through heating.

What is the difference between Chemical Change and Physical Change?

Chemical Change:
-There is a change in energy (Energy is absorbed of given off)
-A new substance is formed (Chemical properties are changed) 
-The process is irreversible (The element(s) used cannot be separated)

E.g. forming of compounds

Physical Change
-There is no change in energy (No energy is absorbed or given off)
-No new substance is formed (Chemical properties stay the same)
-The process is reversible (The element (s) used can be separated by physical means)

E.g. Melting, boiling, sublimation, etc. 

Activity: Heating and Cooling Solids

Materials used
-Sodium Chloride (White solid; crystal form)
-Copper (II) Carbonate (Green solid; powder form)
-Magnesium (Silvery metallic strip, solid form)

Procedures

For Sodium Chloride and Copper (II) Carbonate:
-Gently heat a spatula of the solid in a dry test tube
-If there is no observable change, heat strongly by placing the bottom of the test tube at the hottest part of the flame

For Magnesium:
-Hold the strip of magnesium ribbon using a pair of metal tongs and heat it directly using a Bunsen flame
-DO NOT stare directly at the flame.

Copper (II) Carbonate:
Before heating: Green solid in powder form
During heating: White fumes coming out and black solid formed.
After cooling: No visible change.
Type of change: Chemical change.

Before:                                                                                                  After:

Word equation: Copper (II) Carbonate -------------------------------> Copper (II) oxide + Carbon dioxide
                                                             (Thermal decomposition)


Sodium Chloride:
(Didn't manage to get any pics. :/)
Before: white solid in crystal form.
During heating: Melted into a clear liquid (molten Sodium Chloride)
After cooling: Solidified to form back a white solid.
Type of Change: Physical Change.



Magnesium:
(Didn't manage to get the pics of the reaction cause we were too busy freaking out. :p But it was super cool. :))

Before heating: Silvery metallic strip

During heating: It burned with a bright light (REALLY bright)

After cooling: White powdery solid (Ash) 

Type of Change: Chemical change.

Before:          
                                                                                                               After:

Word equation: Magnesium + oxygen ------------------> Magnesium Oxide
                                                             (Combustion)

Lab session 4

Crystallization

As promised, today we did an experiment on crystallization. In this practical, we formed Copper (II) Sulfate crystals. 

 Materials needed:
- Copper (II) Sulphate (powder form)
-Distilled water
- Spatula
- Filter funnel
- Filter paper
- Boiling tube
- Evaporating dish
- Beaker
- Bunsen Burner
- Tripod stand + wire gauze
- Glass rod
- Peg / tongs

Step 1: Pour 20ml of distilled water into the beaker. Setting it on the wire gauze on the tripod stand, heat the water to a boil. Stop heating when the water starts to boil.

Step 2: Pour 1 spatula of Copper (II) Sulphate into the hot water. Stir with the glass rod until all of the powder has dissolved.

Repeat step 2 until the Copper (II) Sulfate cannot be dissolved.
Step 4: Filter the solution into the evaporating dish. Use the glass rod to help.

Step 5: Heat the solution in the evaporating dish over the bunsen burner. Stop heating when half of the solvent has evaporated from the solution. DO NOT HEAT TO DRYNESS. (If a crust forms on the surface, add distilled water to dissolve the crust. Stir with glass rod.)

Step 6: Using a pair of tongs, carefully grip the evaporating dish and pour its contents into the boiling tube. Since we're doing slow cooling, leave the boiling tube to cool.

(You can see the crystals starting to form already. :D)

(My friend accidentally spilt a bit on the table and it crystallized immediately. XD)

Now, we'll leave it for a week or so to wait for the crystals to develop. Stay tuned! :)

After a two week wait, here are the crystals formed:

Some Demos: 

IODINE SUBLIMATION: Separating iodine from sand

(Heating of mixture of solid iodine balls and sand)

(As can be seen, the dark purple gas is the iodine gas. Sublimation is the transformation from solid directly to gas.)

Separation funnel

Separating oil from colored water

The separation funnel is used to separate liquids of different densities. Since water is denser than oil, water is collected first, then oil. The separating funnel is controlled by a tap.

Lab session 3

Separation techniques

Today, we did chromatography! (as promised.)

EXPERIMENT TIME!!! XD

Purpose: To separate the dyes in green food colouring

Materials used:

-Capillary tube

-Green food colouring

-Chromatography paper

-Boiling tube

-Pencil

-Ruler

-Distilled water

-Clothes peg

Step 1: Draw a line across the chromatography paper 1.5cm from the edge with a pencil:

Step 2: Using the capillary tube, dot at most 3 drops of Green food coloring on the same spot in the middle of the line. 

Step 3: Fill the boiling tube with distilled water (Just 1.5cm^3 of water will do). 

Step 4: Making sure that there is no water on the sides of the boiling tube touching the chromatography paper, carefully place the chromatography paper into the water, with the water below the pencil line (Use the clothes peg to secure the chromatography paper): 

(Okay, I put more than 1.5cm^3 of water.)

Step 5: Watch the dyes move up! :D (It's really cool)

Step 6: After about 10-15 minutes or so, take out the chromatography paper. Let it dry. I got this:

But most, if not all of my classmates got this:

(I hope I didn't get it wrong. :p)

Mark the solvent front. Now, calculate the Rf values.

What are Rf Values?

Retention Factor (Rf) 

Unknown substances separated by chromatography can be identified by Rf values.

So basically, Rf value = Distance moved by substance / Distance moved by solvent. It should always be less than 1, or else something's wrong.

So... 

Here are my results:

So, yep.

TAKEAWAY FROM LESSON: Paper chromatography separates a mixture of solute with different solubility and degree of adsorption. 

e.g. The more adsorbent the solute, the further up the paper it travels, vice versa. 

!!!!NOTE!!!!

Adsorbent does NOT mean Absorbent. 

Adsorbent: (of a solid) hold (molecules of a gas or liquid or solute) as a thin film on the outside surface or on internal surfaces within the material:charcoal will not adsorb nitrates | the dye is adsorbed onto the fiber.

Absorbent: take in or soak up (energy, or a liquid or other substance) by chemical or physical action, typically gradually: buildings can be designed to absorb and retain heat | steroids are absorbed into the bloodstream. 

(Taken from dictionary)