Chem practical 1
When sand is heated over a flame in air, the spatula turns bright red, but the sand appears unchanged. A chemical change occurs.
disagree, nothing happened
Ice cube was:
endothermic
With violates you should always work under a:
hood
physical changes:
- Breaking a beaker - melting of an ice cube - adding water to 6 M HCl to dilute (make it thinner) it
What are the main goals for performing Physical and Chemical Changes?
- Construct definitions for chemical and physical change based on observations. - Perform and observe processes and characterize as chemical or physical change. - Construct criteria for chemical versus physical change. - Examine known chemical and physical changes using common chemicals.
Magnesium strip put under a flame:
bright light, Started out silver and then turned into a white powder - chemical change
When a magnesium strip is heated over a flame in air a bright light is observed and the product looks like grey ash. No chemical change occurs.
disagree, it changed composition
qbulk =
Mass of water * 4.18 * Final - Initial
q warmig =
Mass of water * mass of ice * final
A solid emits a gas:
Might be chemical or physical
Bubbles of gas appear in a liquid:
Might be chemical or physical
ammonium hydroxide chemical formula:
NH4OH
aqueous ammonia formula:
NH4OH
sodium hydroxide formula:
NaOH
Is one indicator enough to know what kind of change occurred?
No
Is heating sand a chemical change?
No, nothing happens to it
Hydrocloric acid with copper:
Nothing happened
Sand put over a flame:
Nothing happened
If a splint glows brightly than the gas is:
Oxygen and be flammable
Sugar dissolves into a liquid:
Physical
Add a scoop of Epsom (magnesium sulfate hydrate) salt to distilled water and 20 drops of drain cleaner
Th salt sunk to the bottom and became a clear homogenous mixture
Potassium Chlorate
The Chlorate started to melt a little but there was still some left that did not really change. The Splint did not seem to be flammable. The pH paper did not change in color. - physical
If it is non flammable:
The bright light will be extinguished
What is enthalpy?
The energy change due to chemical process under pressure. We put the ice in hot water so the melting process would speed up
Red pH paper indicates:
The gas as acidic
If the pH paper is blue:
The gas is basic
As density rises:
The more concentrative the solution is
Copper Sulfate Pentahydrate
The pH paper turned light green. Ph of about 6 or 7. representing a base, and the Copper sulfate in the tube turned from blue to white. Also on the side of the tube there was condensation.
Adding metal to strong acid safety concerns:
a toxic gas may be produced
When sulfur is heated over a flame in air a gas is produced and the sulfur turns into brown goop. A chemical change occurs.
agree
How to get density:
Take mass of sugar/ volume of water
These two should equal:
Zero
Which three things should you always be able to say about your lab notebook?
- When I had problems, I described what happened and how I dealt with it. - If I only had this notebook, I could repeat the work I did today. - If I need to look up a specific observation in 4 years, I will be able to find it.
to find q Melting=
-qbulk - qwarming - Answer should always turn out positive
chemical changes:
-rust forms on a steel bridge beam - baking soda bubbles when vinegar is mixed with it - heating sugar in a flame gives off an unpleasant odor and leaves a black lump where the sugar had been - a match lights and produces a flame when it is struck - a cut apple turns brown after standing in air - carbon dioxide gas bubbles form in cake batter due to heating baking powder
What was the most precise measurement:
10 mL graduated cylinder, would have been pipette but we don't have enough experience
Vaue for enthalpy:
6000 j/mol
heating potassium chlorate in a test tube safety concerns:
Avoid contact with the rubber stopper since since this could result in explosion
baking soda (sodium bicarbonate) added to 1 mL of vinegar (acidic Acid)
Baking soda bubbled up when put with vinegar, and then settled at the bottom, it never dissolved and continued to bubble, baking soda stayed white, vinegar stayed clear - chemical change
Sugar on on bunsen burner flame:
Boiled and turned a brown color, left residue on spatula - chemical change
Burning substances in a direct flame safety concerns:
Bright light could be produced which should not be looked at directly
Zinc + Hydrochloric acid:
Zinc did not change but water started to bubble, everything stayed the same color - physical
vinegar formula:
CH3COOH(aq)
What are some physical properties?
Color, odor, texture, state
You should always add acid to water...
Do not add water to acid, it could start boiling violently
Both of those mixed with ammonia:
Formed layer of blue with dark blue on the top, Pentahydrate was darker than the copper sulfate - chemical
Nitric acid with copper:
Gold , Copper started to bubble and water changed from white to blue, copper turned a lighter color - chemical
6 M Hydrochloric acid safety concern:
High concentration making it explosive
6 M aqueous ammonia (ammonium hydroxide) safety concerns:
High concentration making it explosive, could make you cry so used under a hood
Added ice to hot water:
Ice melted slowly and floated on top, when the ice melted the bubbling stopped - physical change
Sulfur safety concerns:
Produces a toxic gas when burned
Precision is determined by:
Standard deviation
Sulfur put over a flame:
Starts out yellow and powdery. Bubbled and changed from red to black in substance. Became a liquid and then cooled on spatula. end color was black -chemical change
potassium chlorate safety concern:
Strong oxidizer avoid contact with organic material like rubber
Dry ice on watch glass on top of beaker of boiling water:
Sublimation happened, it skipped liquid stage, Frost was on the watch glass - physical change
Sugar added to 1 mL of distilled water:
Sugar settles at the bottom, sugar dissolved slowly, this becomes a homogenous mixture, physical change
uSO4•5H2O (sulfate pentahydrate) with water added:
The water turned blue, while the the pentahydrate sunk to the bottom and turned white
Water + copper sulfate:
The water turned light blue, some of the copper sulfate dissolved - chemical
Potassium thiocyanate + iron chloride
They turned a dark red liquid - chemical
A drop of universal indicator added to vinegar
Turned purple
Universal indicator added to drain cleaner (M sodium hydroxide):
Turned red
2 drops of universal indicator added to 1 mL distilled water then diluted with 2 mL distilled water:
Universal indicator starts out brown, than when added with water turns yellow, no movement - chemical change
3. Consider dissolving sugar in water and magnesium sulfate in water. Is any new substance being produced? What happens after sodium hydroxide is added? Does a new substance appear? Evidence for this?
Water and sugar is just a physical change, when magnesium sulfate is added a new substance is produced
Water + copper sulfate pentahydrate:
Water turned blue, and sunk to the bottom - chemical
q warm should be:
negative energy
Is dissolving sugar in water a chemical change?
no
Basic:
pH greater than 7
Acidic:
pH less than 7
Ammonium Carbonate
pH turned blue. Ph of about 8. This represents that the gas was basic. The gas is flammable because the splint kept burning. The substance evaporated
To find q bulk =
q warming + q melting
q cold should be:
should be positive energy
Experiments must go in the correct:
waste container
Independant variable is on the:
x axis
Dependent is on the:
y axis
