UNIT 4

MATTER

UNIT 4 – MATTER

1. MATTER AND MATERIALS

2. CONDUCTORS AND INSULATORS

3. MIXTURES AND SOLUTIONS

4. PHYSICAL AND CHEMICAL CHANGES

1. MATTER AND MATERIALSThe atom is the smallest particle of matter. It is extremely small and special

microscopes are needed to see one.

A molecule is made when two or more atoms join together. Water H2O is formed by molecules that consist of two atoms of hydrogen (H) and one of oxygen (O)

Pure substances are made of one type of atom or one type of molecule. There are two types ofpure substances:

Elements are made of atoms. For example Gold (Au) calcium (Ca) carbon (C ) Compounds are made of molecules. For example: water (H2O) carbon dioxide (CO2)

All the elements are represented by one or two letters in the periodic table of elements.

Here are some that are familiar to us.

Some examples of compounds that we use in our daily life are (do not learn the formulas, only the names)

H2O2 Oxygenated water NaCl Salt NaClO Bleach

CH3CH2CH2CH3 Butane NH3 ammonia CH3CH2OH Alcohol

CH3COOH Vinager NaHCO3 bicarbonate C6H807 citric acid (used when somebody has stomach ache) (we can find it in lemons)

C3H6O3 lactic acid

(we can find it in dairy products)

CH4 Methane (gas used in heatings)

EXERCISES1. Complete the chart with the name of the atom or its symbol using the periodic table ofelements.

ATOM Hydrogen

Oxygen

Gold Nitrogen

Fluorine

SYMBOL

C Fe Ag Al K

ATOM Calcium

Helium Iron

SYMBOL

Cl Hg

2. Which materials would you use to make the following objets/items and why (say theproperties of materials those objects need).

T – shirt, bridge, cupboard and a pair of glasses.

EXERCISES’ ANSWERS1. Complete the chart with the name of the atom or its symbol using the periodic table ofelements.

ATOM Hydrogen

Carbon Oxygen

Iron Gold Silver Nitrogen

Aluminium

Fluorine

Potasium

SYMBOL

H C O Fe Au Ag N Al F K

ATOM Calcium

Clorine Helium Mercury

Iron

SYMBOL

Ca Cl He Hg Fe

2. Which materials would you use to make the following objets/items and why (say theproperties of materials those objects need).

T – shirt: cotton because is soft and flexibleBridge: steel, wood or concrete because they are toughCupboard: ceramic because is hardPair of glasses: glass because is transparent, metal because is tough

2. CONDUCTORS AND INSULATORSMolecules in matter are never still. Sometimes they move slowly and sometimes they movequickly. We can’t see this movement but we can feel it as heat.

Let’s see as an example the water.

At low temperatures, molecules move very At high temperatures, the molecules in slowly in an ice cube. boiled water for a cup of tea move quickly.

Water is a thermal conductor. Its molecules are free to move about. This means itcan get very hot. Other examples of thermal conductors would be glass or metal.

Plastic and wood are thermal insulators since their molecules are close togetherand can’t move that easy so that they can’t get hot.

In an iron, the plastic stops the heat from the metal reaching your hand.

In a frying pan when we are frying eggs, themetal gets hot, but we do not burn becausewe use a wooden kitchen utensil and thefrying pan handle is made of plastic.

If we let sunlight rays go through the glass of a magnifying glass we couldburn easily a paper.

EXERCISES1. Review what you’ve learnt and check some ideas about thermal conductors andinsulators watching the following videos.

https://www.youtube.com/watch?v=Ry8yXhCxclA

https://www.youtube.com/watch?v=7VUBSDHFvy0

https://www.youtube.com/watch?v=DmnQD3eEkNk

https://www.youtube.com/watch?v=NuBv5H1cYyE

2. Decide whether the following sentences are true or false. Correct the false ones.

a. Molecules in matter are always stillb. At low temperatures molecules move quickly.c. A thermal conductor never gets hot.d. Plastic and wood are thermal insulators.e. Water molecules can’t move a lot.

3. Draw the molecules in…

Glass Plastic

Complete the following sentences with one of the words: In _______________________ are free to move about In _______________________ the molecules are close together

EXERCISES’ ANSWERS2. Decide whether the following sentences are true or false. Correct the false ones.

a. Molecules in matter are always still FALSE Molecules in matter are always moving

b. At low temperatures molecules move quickly. FALSE At low temperatures molecules move slowly

c. A thermal conductor never gets hot. FALSE A thermal conductor gets hot easily

d. Plastic and wood are thermal insulators. TRUEe. Water molecules can’t move a lot. FALSE

Water molecules can move a lot

3. Draw the molecules in…

Glass Plastic

Complete the following sentences with one of the words: In GLASS are free to move about In PLASTIC the molecules are close together

3. MIXTURES AND SOLUTIONS

When two substances are mixed together they form a mixture. A mixture is not a pure substance.There are two basic types of mixture: heterogeneous mixture and homogeneous mixture.

In a heterogeneous mixture we can see the separate substances. This is because their molecules do not mix.

Some examples would be:

cereals and milk soup ice and refreshment soil

salad oil and water pizza chocolate chip cookies

In a homogeneous mixture we can not see the separate substances. This is because one substance dissolves into the other and their molecules mix.

A homogeneous mixture is also called a solution. The substance that dissolves is called the solute and the substance that dissolves is called the solvent.

Hot chocolate is an example of a solution.Chocolate powder is the solute and milk is thesolvent.

Each chocolate molecule still exists but it is now surrounded by milkmolecules.

When you dissolve a solid in a liquid it looks like itdisappears. Check the mass to know it is still there.

There are examples of solutes and solvents in everyday life.

Blood. Nutrients, oxygen, waste products, carbon dioxyde are solutes.

Shampoo. Water is the solvent, shampoo the solute.

Salt and water. Water is the solvent, salt the solute.

The air is formed by nitrogen, oxygen, carbon dioxide and other gases.

White coffee contains milk and coffee.

EXERCISES1. Decide whether the following situations happen when there is a homogeneous mixture,heterogeneous mixture or both.

You can see separate substances.You can’t see separate substances.The molecules mix.The molecules don’t mix.It’s not a pure substance.It’s a mixture.It’s a solution.

2. Identify the solute and the solvent in the following homogeneous mixtures (solutions)

1 Hot chocolate2 Tomato soup3 Water and shampoo4 Mint tea5 Blood and nutrients6 Lemon flavoured yoghurt

EXERCISES’ ANSWERS1. Decide whether the following situations happen when there is a homogeneous mixture,heterogeneous mixture or both.

You can see separate substances.You can’t see separate substances.The molecules mix.

The molecules don’t mix.It’s not a pure substance.It’s a mixture.It’s a solution.

2. Identify the solute and the solvent in the following homogeneous mixtures (solutions)

1 Hot chocolateSolute: chocolate powder. Solvent: milk

2 Tomato soupSolute: tomatoes. Solvent: water

3 Water and shampooSolute: shampoo. Solvent: water

4 TeaSolute: tea. Solvent: water

5 Blood and nutrientsBlood that circulates in arteries. Solute: nutrients and oxygen. Solvent: bloodBlood that circulates in veins. Solute: waste products and carbon dyoxide. Solvent: blood

6 Lemon flavoured yoghurtSolute: lemon flavour. Solvent: yoghurt

4. PHYSICAL CHANGES AND CHEMICAL CHANGES

Matter can change. There are two types of changes.

In a physical change the molecules move about but their structure doesn’t change. The objectremains but may be in a different state (melted, broken...)

Some examples would be:

Melting an ice cube. Water in solid state turns into liquid state, but it is still water.

Boiling water. We heat the water and turns into gas, but it is still water.

Breaking a bottle. We have a bottle made of glass, if webrake it into pieces, these are still made of glass.

Folding paper, shredding paper. Whenyou fold a sheet of paper to make aplane, the plane is still made of paper.If you shred a written sheet of paper,the tiny pieces are still made of paper.

Flying a kite or a parachute. Both are made ofnylon, which is a type of fabric that adopts adifferent shape since it’s elastic when we fly the

kite or use the parachute, but it is still the same type of matter;nylon.

Freezing yoghurt. It changes its state (from liquid to solid) but it’s still yoghurt.

In a chemical change new molecules are made and the matter is changed forever. The objecthas new properties.

Burning wood. From wood we get different types of matter: smoke and ashes, that are formed by new different molecules.

When food rots mold is formed, which is a different matter.

Rusting of iron. Iron exposed to weather conditions creates rust, which is a different matter.

When milk ferments to make cheese, butter, yoghurt...

EXERCISES1. Decide whether in the following situations a physical or a chemical change happens.

a. melt butterb. freeze waterc. roll plasticined. leave an iron nail in watere. burn paperf. make yoghurt

EXERCISES’ ANSWERS

1. Decide whether in the following situations a physical or a chemical change happens.

a. melt butter physical changeb. freeze water physical changec. roll plasticine physical changed. leave an iron nail in water chemical changee. burn paper physical changef. make yoghurt chemical change

REVIEW EXERCISES

1. Choose the correct answer

a) Which are pure substances?1. Elements and compounds2. Atoms and molecules3. Elements and mixtures

b) Which are thermal insulators?1. Wood and metal2. Glass and plastic3. Wood and plastic

c) Which is the solute in hot chocolate?1. Milk2. Chocolate3. Water

d) Which are physical changes? 1. Changing place and state 2. Burning and rusting 3. Changing temperature and burning

2. Form meaningful sentences

a) Two or more different atoms… 1. the molecules can move aboutb) A pure substance has… 2. join together to make a moleculec) In a thermal conductor… 3. new molecules are formedd) In a solution different molecules form… 4. only one type of atom or moleculee) In a chemical change… 5. the solvent and the solute mix together

REVIEW EXERCISES’ ANSQWERS1. Choose the correct answer

a) Which are pure substances?1. Elements and compounds2. Atoms and molecules3. Elements and mixtures

b) Which are thermal insulators?1. Wood and metal2. Glass and plastic3. Wood and plastic

c) Which is the solute in hot chocolate?1. Milk

2. Chocolate3. Water

d) Which are physical changes? 1. Changing place and state 2. Burning and rusting 3. Changing temperature and burning

2. Form meaningful sentences

a) Two or more different atoms… 1. the molecules can move aboutb) A pure substance has… 2. join together to make a moleculec) In a thermal conductor… 3. new molecules are formedd) In a solution different molecules from… 4. only one type of atom or moleculee) In a chemical change… 5. the solvent and the solute mix together