Homework Ph Chemistry Worksheet (Page 3 of 6) in pdf

Homework Ph Chemistry Worksheet Page 3

Homework 3

Q1. The table below shows the pH of some foodstuffs.

Food

Approximate pH number

Jelly

3.1

Ketchup

3.6

Mayonnaise

3.7

Canned tomatoes

4.0

Meats

5.2-6.9

Soya bean milk

7.0

Crackers

8.2

Milk of magnesia

10.5

a) Which food has a neutral pH value?

b) Name a food to avoid if you already have too much acid in your stomach.

c) Which food is the least alkaline?

d) Which food is the most acidic?

Q2. Read the passage below and answer the questions which follow.

All additives used in foodstuffs must be safe. Many foods go off quickly without

the use of preservatives. It is now known that preservatives prevent the growth of

micro-organisms, some of which are extremely dangerous.

Most preservatives are simple chemicals and are closely related to natural

substances. For example, benzoic acid occurs in several fruits and is widely used in

fruit preservation. Sorbic acid, another preservative, is an unsaturated acid found

in some plants.

Some preservatives have been used for hundreds of years. For example wood

smoke contains a large number of hydrocarbons, some of which can cause cancer.

Dangerous or threatening additives may include the colourings, preservatives,

flavours, flavour enhancers, sweeteners, texture agents and processing agents. As

you can see the list is endless. Details of these must be included on the labelling

(shown as E numbers). Ideally, food that has no additives at all is to be preferred

and especially if it is to be used to feed children. Additives can lead to certain

health complications.

Homework Ph Chemistry Worksheet Page 3