Just a Reminder - Chemistry Practical

Practical Tips
• If you are asked to heat up a substance with sodium hydroxide
and aluminium, don’t assume that ammonia is the gas that is given
off. It could be hydrogen. Get your answer from your observations
not from theory.
• The observation of effervescence is often missed out from practical observations. Look for the bubbles!
• In carrying out titrations you must repeat them until you get at least two consistent results which you can tick. Examiners often find that only one result is ticked – make sure that two are ticked.
• In titrations you must only average the consistent results that you have ticked, not all the titration results.
• When describing solutions do not use the word ”clear” when
you mean colourless. In chemistry, clear just means you can see
through it – it is the opposite of cloudy.
• The word precipitate is often used incorrectly. You can only use it about a solid formed when two solutions are mixed.
• When making observations about a solution don’t forget that ”colourless solution” may also gain a mark. Lack of colour is just as important an observation as presence of colour.
• Take care when adding a solution of sodium hydroxide to test for ions. If you add a large volume of sodium hydroxide too quickly, you may get the precipitate re-dissolving without you ever noticing that one was formed, e.g. in the case of adding sodium hydroxide to aluminium chloride solution.
• When describing colours don’t use combinations e.g. blue-green or yellow-red, unless absolutely necessary for distinction and certainly don’t use contrasting colours, e.g. greenish brown.
• When observing colour changes, make sure that you observe all the colour changes, not just the first and last. For example, when adding silver nitrate to sodium thiosulphate, the colour changes are white → yellow → red → black.
• You must be able to distinguish between the different shades of yellow precipitates, e.g. silver bromide, silver iodide and lead iodide. You can do this by calling them creamy yellow, light yellow, deep yellow etc, but do not write green (a common mistake) when the colour is clearly yellow.

Just a Reminder - Physics Practical

(a) When drawing graphs, you should:
• remember to label the title of the graph
• remember to label the axes with both quantity (e.g. distance or d) and unit (e.g. metres or m). Then write it as distance / metres or even just d / m.
• make sure the axes are the correct way round. You are usually told, for example, to plot distance on the x-axis, so make sure you know that x is the horizontal axis!
• make the scales go up in sensible amounts, i.e. not 0, 3, 6… or 0, 7, 14 … but 0, 5, 10 … or 0, 2, 4 ….
• make sure that the plotted points fill at least half the graph paper. (This means you cannot double the scale and still plot all the points on the graph.)
• make sure you know how many sets of readings you are going to record eg distance d1, d2; corresponding time t1, t2; average time T per oscilation ie T/20 osc; square of T. Then show the tabulation clearly eg d1/m d2/m t1/s t2/s T/s T2/s. If you do not have time to take the 2 sets of readings, you must at least take 1 set of reading accurately first.
• check if you have been told to start the scales from the origin. If not, then think carefully about where to start the axes.
• use a sharp pencil to plot the points and draw the line.
• plot the points carefully. It is best to use small neat crosses. Every point will be checked by the marker, and you will lose the mark if any are wrongly plotted.
• draw either a straight line or a smooth curve. In physics we never join the dots!
• remember that a best fit line (curve or straight) should have some points both above and below the line.

(b) When taking readings from a graph, you should:
• draw a large triangle when measuring the gradient of a line.
It must be at least half the length of the line. Examiner’s
tip – draw a triangle the full size of the graph!
• always use points on the line, not your plotted points, when calculating the gradient.
• draw a tangent to find the gradient of a curve. Make sure it is at the right place on the curve. Again, use a large triangle.
• make sure you read the scales correctly when reading a value from a graph. It may be that they are in mA rather than A or km rather than m.

(c) When describing the shape of a graph, remember that:
• directly proportional means a straight line through the origin. In this case, doubling one quantity will cause the other to double.
• if the straight line does not go through the origin, then it is just called a linear graph.
• if doubling one quantity causes the other to halve, then they are inversely proportional.
• if increasing one quantity causes the other to decrease, it is called an inverse relationship.

(d) When drawing circuit, please remember to label the individual components.

(e) When a formula is given, please substitute and calculate the values correctly.

Drinking Tea

Something to share with everyone here.

Drink less coffee. Tea is better.

Are you drinking the right tea?

1. People who use their "brain" to work or students who study hard
day and night --- should drink more chrysanthemum Tea.

2. People who need a lot of body energy to work or those people that
do a lot of exercise everyday --- should drink Wu Loong Tea.

3. People who travel on a bike or work in dirty and polluted places
--- should drink Green Tea.

4. For people who likes to sit down all day long and not doing
anything even exercising--- must drink Green Tea and Flower Tea.

5. People who smoke and drink alot of alcoholic drinks
--- should drink more Green Tea.

6. Carnnivore ( those people who must eat meat at least once a day,
or feel sick or not feeling well--- try to drink some Wu Loong Tea.

7. People who go to the washroom too often or too less
--- should drink more Honey Tea

8. People with high cholesterol and high blood pressure
--- Wu Loong Tea,Green Tea.

9. Those who work with computers everyday
--- need to drink a Lot of Tea (any tea will do).

Whenever you are working with the computer, you should make some
tea, drink it when you are free.

Drinking Tea is healthy, it can protect and prevent the harmful
Ultraviolet light from harming us (when using computer).

Furthermore, it can also cure us when we are tired and help making
our body feel fresh again.

Diet Myths Exposed

Diet Myths Exposed: Part 1
Posted by Joy Bauer, M.S., R.D., C.D.N.
on Mon, Oct 02, 2006, 10:29 am PDT

The following diet myths come up over and over again at my nutrition center. My next two blog entries will help set the record straight. Hope you find this helpful!

• If you eat late at night, the food turns straight into fat.

Not true.If your overall calories are appropriate for weight loss, you certainly can eat something after dinner. Late night calories will ultimately get used the next day (and even while you sleep).
However, for the sake of energy, it is always better to eat your calories during the day when your body needs the fuel. Plus, eating consistently throughout the day will stabilize blood sugar levels -- so you’ll feel energized and experience fewer cravings. If you are going to snack after dinner, I suggest choosing something 250 calories or less.

• Fresh fruits and vegetables are more nutritious than frozen.

Not necessarily. Frozen can be a great produce option (just avoid varieties with added salt, sugar, and sauce). Frozen foods are picked in the peak of ripeness, then frozen. You can eat them as you need them -- and most of the nutrients are locked in. On the other hand, fresh fruit and vegetables are typically harvested before they ripen, and can have nutrient variability. Also, the longer fresh produce sits around in your fridge, the less nutrients it will contain.
Bottom line: Buy both fresh and frozen and eat as much as you can.

• Cravings are your body's way of telling you it needs something.

This has never been proven. You normally crave what you like to eat (or smell or see someone else eating). Also, hormonal changes are sometimes responsible for food cravings. Ice cream and pickles anyone?

• Any type of water is always better than soda.

No. There are a few caloric waters with sexy marketing ploys. In fact, some brands have quite a bit of sugar. Always check labels.

• Certain foods, like grapefruit, celery, or cabbage soup can burn fat and make you lose weight.

These are anecdotal stories that have no scientific back up. It’s true these foods are low in calories, but they do NOT actually burn fat.

Metabolism: How It Works

Metabolism: How It Works
Posted by Joy Bauer, M.S., R.D., C.D.N.
on Thu, Jul 27, 2006, 11:13 am PDT

A lot of my clients often complain that they can't lose weight because of a "slow metabolism." And, unfortunately, many companies capitalize on this belief by marketing products that promise a so called "metabolic advantage" to help melt away the pounds. My next blog entries will discuss everything you need to know about metabolism. Hope you enjoy!
So What Is Metabolism?
Metabolism is the process (or rate) by which your body converts calories from food into energy. People often believe that a slim person's metabolism is high and an overweight person's metabolism is low, but this isn't usually the case.
Metabolism alone does not determine your weight. Rather weight is dependant on the balance of calories consumed versus calories burned.
• Take in more calories than you need -- you gain weight.
• Take in less calories than you need -- you lose weight.
Metabolism is merely the engine that burns these calories and the scale that regulates your calorie needs.
Your metabolism (the amount of calories your body burns each day) involves three key things:
1. Basic Needs -- This is known as your basal metabolic rate and covers the calories needed to sustain vital body functions; fuel for organs, breathing, circulating blood, adjusting hormone levels, plus growing and repairing cells. Typically, a person's basal metabolic rate makes up 66 to 75% of the total calories the body requires for the day.
2. Digestion and Absorption of Food -- About 10% of your day's calories go towards the digestion and absorption of the food you eat. It's ironic that you actually need calories to burn calories.
3. Physical Activity -- Exercise, depending upon how active you are each day, accounts for the remainder of calories burned.