Week 2 Chemistry

Water molecule

A molecule composed of two hydrogen atoms and one oxygen atom, exhibiting di-polar properties.

Di-polar molecule

A molecule with regions of partial positive and negative charges.

Solvent properties

Unique characteristics of a substance that enable it to dissolve other substances.

Hydrogen bonding

The attractive force between a hydrogen atom in one molecule and an electronegative atom in another molecule.

Hydrogen bonds

Weak bonds formed between hydrogen atoms and other electronegative atoms, such as oxygen or nitrogen.

Polarity

The property of a molecule having a positive and negative end, caused by an uneven distribution of electrons.

Boiling point

The temperature at which a substance changes from a liquid to a gas, in the case of water, it is 100 degrees Celsius at sea level.

Molecular bonds

The attractive forces between atoms or molecules that hold them together.

Steam

The gaseous form of water that is produced when water reaches its boiling point and undergoes a phase change.

What type of bonding holds water molecules together within a single molecule?

Covalent Bonding

How do water molecules interact with each other?

Via intermolecular hydrogen bonding

Is hydrogen bonding a strong or weak bond?

Weak bond

What is happening in hydrolysis and condensation reactions?

Chemical reactions are occurring in which molecules are broken down (hydrolysis) or combined (condensation).

How does enzymatic hydrolysis contribute to digestion?

Enzymatic hydrolysis breaks down proteins into peptides and amino acids during digestion.

What is the Maillard reaction?

The Maillard reaction is a cooking process where a reducing sugar or polysaccharide reacts with a protein or peptide, forming a complex mixture of compounds that contribute to the flavor and color of cooked food.

What is a hydrolysis reaction?

a chemical reaction that uses a water molecule to break a chemical bond.

What does the term 'hydrolysis' mean?

the addition of a water molecule in a chemical reaction.

Give an example of a hydrolysis reaction

production of lactose-free milk,

What happens when salt comes into contact with water?

It dissociates into sodium and chloride ions.

What type of bonds hold sodium chloride (NaCl) together?

Ionic bonds.

What is the common occurrence when ionic compounds interact with water?

Dissociation.

What are some examples of cellular processes in the body that involve salts?

Blood and fluid balance.

What happens to the hydrogen bonds in water when salt is added?

They rearrange.

What are the two ions that sodium chloride dissociates into?

Sodium and chloride ions.

What is the charge of a sodium atom?

Positively charged.

Which side of the water molecules move to surround the sodium atom?

The negative (oxygen, red) side.

Why do the water molecules surround the sodium atom?

To neutralize the positive charge of the sodium atom.

What is chloride?

A negatively charged atom.

How do water molecules react to chloride?

The positive regions of water molecules move to surround and neutralize the negative charge of chloride.

What is the water content range in foods?

The water content in foods can range from 0-95%.

Which foods have a high water content?

Fruits and meat

What is the water content range in foods with a high proportion of lipids (fats)?

10-20%.

What is the water content in dry foods like dehydrated grains?

Dry foods like dehydrated grains may have a water content of 0%.

What is bound water?

Water molecules are very tightly bound within the chemical structure of another molecule and cannot freely move.

What is required to remove bound water from its bound state?

energy

Which types of foods have a high proportion of bound water?

carbohydrates, lipids (fats), and proteins.

What are the properties of bound water that make it useful in food preservation and cooking?

Bound water can be very helpful in food preservation and cooking, as bound water is resistant to freezing and drying. 

What is free water?

Water that is easily removed and can act as a solvent for salts, acids, or sugars.

Where is free water stored in animal and plant tissues?

Within the cells.

How can free water be observed in a piece of fruit?

When the cells of the fruit are cut open, water stored within the cells' vacuoles freely moves out of the cell walls.

What is the shape of a water molecule?

Tetrahedral

What is the range of water activity (aw) measurement?

0.00 (lowest) to 1.00 (highest)

At what water activity level is food spoilage inhibited?

Below aw 0.85

How can microbial growth be lowered in preserved foods?

By lowering water activity through the addition of sugar and salt

What is the purpose of adding sugar and salt to preserved foods?

To bind free water and reduce available water, inhibiting microbial growth and preserving the food.

What is osmosis?

Osmosis is the net movement of water to a solute through a semipermeable membrane.

What is a semipermeable membrane?

A semipermeable membrane is a membrane that allows certain substances to pass through while blocking others.

What creates osmotic pressure?

An uneven gradient of solute creates osmotic pressure.

What happens during osmosis?

Water diffuses out through the cell wall membrane to achieve equilibrium of solute concentration on both sides of the membrane.

What are colligative properties of water?

describes the way water behaves in a solution, depending on the number of molecules present in a defined volume of water, rather than the chemical structure of the molecule and its own properties. 

What is a solvent?

A substance, usually a liquid, in which another substance is dissolved.

Give an example of a solvent

Water is the solvent in a saline solution.

What is a solute?

A solid, liquid, or gas dissolved in another substance.

Provide an example of a solute

Salt is the solute in a saline solution.

Define solubility

Solubility refers to the degree or ability of a substance to blend uniformly with another.

Give an example of a substance with high solubility

Salt has a high solubility in water.

What is saturation?

when a liquid can no longer dissolve a solute, resulting in the formation of a precipitate (solid).

What is a true solution?

A true solution is a mixture in which all particles are completely dissolved, and no precipitate (solid) forms. It has no gravitational pull.

Define dispersion

Dispersion refers to mixtures that contain particles that are dispersed within another substance.

What is a solution?

Particles that come from a uniform (homogenous) mixture of two or more substances that are evenly distributed.

Give examples of solutions.

Saline (salt in water), Alcohol (alcohol in water), Sugar (solid in water), Carbonated water (gas in water)

What are the properties of a solution?

Particles are small once dissolved and cannot be seen with the naked eye. They can't be separated by filtering and won't precipitate out.

What is a suspension?

A heterogenous mixture of undissolved particles in a medium (water).

Give an example of a suspension

Oil in water.

What are the properties of a suspension?

Non-uniform composition, particles can be seen with the naked eye, and over time, gravity causes visible layers to appear.

What happens to a suspension when it is shaken?

It becomes suspended.

What happens to a suspension when it is left undisturbed?

It separates into layers.

What is a colloid?

An intermediate state between a suspension and solution.

Give an example of a colloid.

Milk (water and fat).

What is an example of a foam colloid?

Whipped cream or whipped egg white.

What is an example of an emulsion colloid?

Mayonnaise, milk, and butter.

What are some properties of colloids?

The particles are small and suspended over time into layers and will not separate.