So what is a carat?
What do those numbers mean?
How can "gold" be different colours?
What do those numbers mean?
How can "gold" be different colours?
Read all about it in the June 2019 issue of AUS-e-NEWS
Showing posts with label percent by mass. Show all posts
Showing posts with label percent by mass. Show all posts
Friday, May 31, 2019
24 Carat Chemistry
I was trying to buy a present for my mum for Mothers' Day.
"A gold chain," I thought, "would be a nice present". But
when I got to the jewellery shop I found that there is a huge variety of
"gold chains", 24 carat gold, 18 carat gold, 9 carat gold, 995, 750,
375, white gold, rose gold...
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Thursday, November 2, 2017
Spud Lite?
"Spud Lite", the advertising poster said, "25% less carbs", followed in fine print by "than other potatoes".
"How strange", I thought, "I thought you ate potatoes for their carbohydrate (carbs) content so why would you want a potato with less carbohydrate?"
But then I started thinking about what this meant in terms of the chemical composition of the potato. If it contains 25% less carbohydrate, then surely that means something else must have been increased or added? Or are you just getting less potato for your money?
Typically, a traditional potato has the following approximate composition:
That is, 100 g of traditional potato contains about 79 g of water, 17.5 g of carbohydrate, 2 g of protein and 0.1 g of fat.
One way to reduce the percentage of carbohydrate in a potato would be to reduce the density of the potato.
If 100 g of a traditional potato had a volume of 92 mL, then the density of the potato would be 1.09 g/mL. 1 mL of traditional potato has a mass of 1.09 g and contains 17.5% by mass (0.19 g) of carbohydrate.
If "spud lite" has a lower density of potato "flesh", say 0.8 g/mL, then 1 mL of "spud lite" has a mass of 0.8 g and contains 17.5% by mass (0.14 g) of carbohydrate.
If we then compare equal volumes (sizes) of potatoes, say 1 mL of traditional potato and 1 mL of "spud lite" we find that "spud lite" contains 100 x (0.19 - 0.14)/0.19 = 26% less carbohydrate (by volume!).
But, if the density of "spud lite" is less, the % by mass composition remains the same, that is, for every 100 g of potato (traditional or "spud lite") there will be 17.5 g of carbohydrate (but the "spud lite" potato will be a bigger potato for your 100 g).
The nutrition label on a packet of "spud lite" potatoes gives the following masses per 100 g of potato:
(assuming the dietary fibre is cellulose which is also a carbohydrate).
This means that the actual mass of carbohydrate per 100 g of potato has been decreased. That is, "spud lites" are not just less dense than traditional potatoes.
Another way to decrease the proportion of carbohydrate in your potatoes would be to increase their water content.
Imagine you have 100 g of traditional potato. This potato is made up of 79 g of water and 17.5 g of carbohydrate.
"Spud lite" contains 11.4 g of carbohydrate.
Further Reading
Experimental Design
Carbohydrates
Proteins
Lipids (fats and oils)
Percentage Composition
Density
Suggested Study Questions:
"How strange", I thought, "I thought you ate potatoes for their carbohydrate (carbs) content so why would you want a potato with less carbohydrate?"
But then I started thinking about what this meant in terms of the chemical composition of the potato. If it contains 25% less carbohydrate, then surely that means something else must have been increased or added? Or are you just getting less potato for your money?
Typically, a traditional potato has the following approximate composition:
| nutrient | % by mass |
|---|---|
| water | 79 |
| carbohydrate | 17.5 |
| protein | 2 |
| fat | 0.1 |
That is, 100 g of traditional potato contains about 79 g of water, 17.5 g of carbohydrate, 2 g of protein and 0.1 g of fat.
One way to reduce the percentage of carbohydrate in a potato would be to reduce the density of the potato.
If 100 g of a traditional potato had a volume of 92 mL, then the density of the potato would be 1.09 g/mL. 1 mL of traditional potato has a mass of 1.09 g and contains 17.5% by mass (0.19 g) of carbohydrate.
If "spud lite" has a lower density of potato "flesh", say 0.8 g/mL, then 1 mL of "spud lite" has a mass of 0.8 g and contains 17.5% by mass (0.14 g) of carbohydrate.
If we then compare equal volumes (sizes) of potatoes, say 1 mL of traditional potato and 1 mL of "spud lite" we find that "spud lite" contains 100 x (0.19 - 0.14)/0.19 = 26% less carbohydrate (by volume!).
But, if the density of "spud lite" is less, the % by mass composition remains the same, that is, for every 100 g of potato (traditional or "spud lite") there will be 17.5 g of carbohydrate (but the "spud lite" potato will be a bigger potato for your 100 g).
The nutrition label on a packet of "spud lite" potatoes gives the following masses per 100 g of potato:
- fat < 0.1 g
- protein 1.4 g
- carbohydrate: 8.9 g
- sugars: 1.1 g
- dietary fibre: 1.4 g
(assuming the dietary fibre is cellulose which is also a carbohydrate).
This means that the actual mass of carbohydrate per 100 g of potato has been decreased. That is, "spud lites" are not just less dense than traditional potatoes.
Another way to decrease the proportion of carbohydrate in your potatoes would be to increase their water content.
Imagine you have 100 g of traditional potato. This potato is made up of 79 g of water and 17.5 g of carbohydrate.
"Spud lite" contains 11.4 g of carbohydrate.
If all the lost mass of carbohydrate in the "spud lite" (17.5 - 11.4 = 6.1 g) was present as water, then the mass of water in "spud lite" = 6.1 + 79 = 85.1 g
And you, the consumer, is just paying for additional water in your potato!Further Reading
Experimental Design
Carbohydrates
Proteins
Lipids (fats and oils)
Percentage Composition
Density
Suggested Study Questions:
- Design an experiment to test the hypothesis that "spud lite" potatoes have a lower density than traditional potatoes.
- Design an experiment to test the hypothesis that "spud lite" potatoes have a greater percentage by mass of water than traditional potatoes.
- For each serving of traditional potato given below, calculate the mass of carbohydrate consumed:
- 25 g of potato
- 75 g of potato
- 135 g of potato
- Calculate the mass of "spud lite" you would have to consume in order to obtain
- 1 g of carbohydrate
- 7 g of carbohydrate
- 21 g of carbohydrate
- The density of potato changes as the potato ages on the shelf. The table below shows the results of an experiment in which the mass and volume of the same potato is measured and recorded every 3 days. Calculate the density of the potato on each day.
Day Mass (g) volume (mL) 1 142 130 4 140 129 7 138 128 - Consider the results of the experiment above. Describe any trends that you see in the data and suggest reasons for these trends.
- Explain what chemists mean when they refer to "carbohydrates".
- The nutrition label on "spud lites" lists the mass of carbohydrate, sugars and dietary fibre separately. What do you think the "carbohydrate" is on this label?
- Add together the percent by mass of all the components listed for a traditional potato.Suggest reasons for why the total percentage is less than 100%.
- Potatoes are usually classified as high on the glycemic index (GI). What does this mean?
Thursday, March 24, 2016
Hidden Salt in Food
Researchers at VicHealth and Deakin University compared how much salt people thought they consumed with how much salt they really had consumed and found that Australians were not only eating too much salt, but were also eating more salt than they thought they were!
Australians were found to be consuming between 8 and 10 grams of salt per day, about twice the amount recommended by the World Health Organisation (WHO) that recommends adults should eat less than 5 g of salt (a bit less than a teaspoon) per day. The "salt" they are referring to is "table salt" which has the chemical name "sodium chloride" and the chemical formula NaCl. Sodium chloride is actually an ionic substance made up of sodium ions (Na+) and chloride ions (Cl-) in a ratio of 1:1 and it is the sodium ions (Na+) that are the cause for concern because elevated levels of sodium ions increase a person's risk of high blood pressure, heart disease and stroke. Unfortunately, non-Chemists often refer to this as elevated "sodium" levels rather than as elevated "sodium ion" levels.
If you want to reduce your sodium chloride intake, the first thing you can do is NOT add "table salt" to your food when you eat it. However, only about 20% w/w of our daily intake of sodium ions comes from adding sodium chloride to our food at the table before we eat it. The other 80% w/w of the sodium ions we consume is already present in our food, either naturally or because it has been added during processing.
Natural sources of sodium ions in our food include:
Many people forget that sodium ions are also present in many medicines. Effervescent medicines contain sodium hydrogen carbonate (or sodium bicarbonate) which helps them dissolve in water.
For example,:
Reference:
http://www.abc.net.au/news/2016-03-24/reducing-salt-intake-could-save-thousands-of-lives-each-year/7274140
Australians were found to be consuming between 8 and 10 grams of salt per day, about twice the amount recommended by the World Health Organisation (WHO) that recommends adults should eat less than 5 g of salt (a bit less than a teaspoon) per day. The "salt" they are referring to is "table salt" which has the chemical name "sodium chloride" and the chemical formula NaCl. Sodium chloride is actually an ionic substance made up of sodium ions (Na+) and chloride ions (Cl-) in a ratio of 1:1 and it is the sodium ions (Na+) that are the cause for concern because elevated levels of sodium ions increase a person's risk of high blood pressure, heart disease and stroke. Unfortunately, non-Chemists often refer to this as elevated "sodium" levels rather than as elevated "sodium ion" levels.
If you want to reduce your sodium chloride intake, the first thing you can do is NOT add "table salt" to your food when you eat it. However, only about 20% w/w of our daily intake of sodium ions comes from adding sodium chloride to our food at the table before we eat it. The other 80% w/w of the sodium ions we consume is already present in our food, either naturally or because it has been added during processing.
Natural sources of sodium ions in our food include:
- milk and cream: 50 mg of sodium ions per 100 g
- eggs: 80 mg of sodium ions per 100 g
- carrot: 69 mg of sodium ions per 100 g
- spinach: 79 mg of sodium ions per 100 g
- green beans, potatoes: 6 mg of sodium ions per 100 g
- pumpkin: 1 mg sodium ions per 100 g
- apple, banana, pear: 1 mg sodium ions per 100 g
By far the greatest source of sodium ions in our diet comes from eating processed foods:
- 1 slice of white bread (30 g) can contain 140 mg Na+
- 1 slice of cheddar cheese (20 g) can contain 140 mg Na+
- 1 foil pack of butter (7 g) can have 55 mg of Na+
- 1 small bowl of breakfast cereal (30 g) can have 140 mg of Na+
- 1 small packet of potato chips (45 g) can have about 300 mg of Na+
- 1 can (12 fl oz, about 350 mL) diet coke has 40 mg of Na+
- tap water contains about 20 mg Na+ per 1 L
Food you buy in packets from a supermarket will have a list of ingredients and you can read this to find the amount of sodium ions (Na+) present in the food.
However, there are many foods we buy that do not come in a packet which tells us how much sodium ion is present. These foods make up our "hidden salt intake". You may find this information on company websites, such as
However, there are many foods we buy that do not come in a packet which tells us how much sodium ion is present. These foods make up our "hidden salt intake". You may find this information on company websites, such as
- 1 McDonalds Big Mac contains 859 mg of Na+
- 6 KFC chicken nuggets with sauce has 1040 mg of Na+
- 1 slice (1/8 th) of medium pan Pizza Hut Meat Lover's pizza has 740 mg of Na+
- 1 Taco Bell black bean burrito contains 1030 mg of Na+
For example,:
- 1 effervescent Berocca tablet contains about 280 mg of Na+ while the film-coated Berocca tablet contains only 1.85 mg of Na+
- 1 Gaviscon Advance tablet contains 55 mg Na+ but 10 mL of liquid Gaviscon contains 141 mg of Na+
- 1 Panadol Actifast caplet contains 173 mg Na+ but 1 Panadol soluble tablet contains 428 mg of Na+
Reference:
http://www.abc.net.au/news/2016-03-24/reducing-salt-intake-could-save-thousands-of-lives-each-year/7274140
Further Reading:
Mass Conversions
Percent by Mass
Suggested Study Questions:
Mass Conversions
Percent by Mass
Suggested Study Questions:
- Convert the following masses in grams to masses in milligrams:
- 5 g
- 8 g
- 10 g
- 30 g
- 100 g
- Convert the following masses in milligrams to masses in grams:
- 1.85 mg
- 55 mg
- 69 mg
- 173 mg
- 859 mg
- 1040 mg
- Calculate the percentage of sodium ions and the percentage of chloride ions in sodium chloride.
- Use the information in the article to calculate the mass of sodium ions each adult Australian currently consumes as a result of :
- adding table salt to food before eating it
- table salt that is naturally present or is added to food during preparation
- 100 g of milk contains 50 mg of Na+ . What is the percentage by mass of sodium in the milk?
- One 30 g slice of white bread contains 140 mg Na+. What is the percentage by mass of sodium in white bread?
- For lunch, a student ate a sandwich made up of 2 slices of white bread, 2 foil packs of butter and a slice of cheddar cheese. She also ate a 200 g banana, and washed it all down with 250 mL of plain, unflavoured milk.
- Calculate the mass of sodium ions the student consumed for lunch.
- Calculate her consumption of sodium ions as a percentage of the WHO recommended daily intake of sodium ions.
- A different student consumed a Big Mac, 1 can of diet coke, and a 200 g packet of potato chips.
- Calculate the mass of sodium ions the student consumed for lunch.
- Calculate her consumption of sodium ions as a percentage of the WHO recommended daily intake of sodium ions.
- For her birthday, a Chemistry Teacher's class gave her a 500 g block of dairy milk chocolate. The label included the information that the block of chocolate contained 82 mg of sodium per 100 g.
- What is the mass of sodium ions in the block of chocolate?
- If each person in the class of 22 received an equal share of the block chocolate, what mass of sodium ions would each person consume?
- In Australia, the maximum recommended dose of paracetamol (the active ingredient in panadol tablets) is 4000 mg per day. 1 soluble Panadol tablet contains 500 mg of paracetamol.
- What is the maximum number of soluble Panadol tablets per day that an adult Australian should consume?
- If an adult Australian consumed the maximum recommended dose of soluble panadol tablets in 1 day, what mass of sodium ions would they have consumed?
- What percentage of the WHO recommended maximum intake of sodium would this amount of panadol be?
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