SCIENCE REVIEW

TEST READINESS

Properties of Matter Brittleness - the property of matter that is how

easily the substance breaks or shatters when force is applied to it.

Ductility - property of a metal in which it can be stretched without breaking.

Elasticity - the ability of a substance to be stretched and then to return to its original shape.

Hardness - property of matter that determines how easily the substance can be scratched.

Malleability - the property of a metal that allows it to be hammered, rolled, pressed or forged.

HOW DOES ONE STUDY FOR A LAB?

HOW DOES ONE STUDY FOR A LAB?

Practice with the tools, e.g. thermometer, scales, weighing tray, stopwatch, calculators

Practice making graphs, especially line graphs (x: time, y: temperature), using data tables

Memorize the definitions of key science words Use other sources for quizzing, e.g. BrainPop,

aboutChemistry.com Make own quiz/test Have a peer/parent quiz you on

definitions/method

KEY WORDS: CHEMICAL CHANGE

Chemical change Endothermic reaction Exothermic reaction

CHALLENGE

Is cooking an example of chemical or physical

change?

Cooking

When most of the food is cooked, it can not be reversed to the original substance it was in before cooking it, for example, when meat is cooked it changes the color.

chemical change A chemical reaction is a chemical change which forms new

substances; the starting materials (reactants) are different from the product

When a chemical change takes place there is the change of temperatures where there might be loss of heat but in most chemical change reactions heat or energy is produced.

Another characteristic of a chemical change is the change in color. For example when an iron nail comes into contact with water, the nail begins to rust and its color change from silver to reddish brown meaning that chemical change has taken place.

The production of gases and solids is also another characteristic of a chemical change. The gases produced appear in the form of bubbles as a result of the reaction. A solid maybe formed and it separates itself from the solution after the reaction.

BrainPop Movie

http://www.brainpop.com/science/matterandchemistry/propertychanges/preview.weml

Endothermic reaction An endothermic reaction is any chemical reaction that

absorbs heat from its environment. It is a reaction that requires energy to proceed. The intake of energy may be observed as a decrease in temperature as the reaction proceeds. Once the reaction is complete, the temperature of the mixture will return to room temperature.

Examples

1.

2. reacting ethanoic acid with sodium carbonate

3. photosynthesis (chlorophyll is used to react carbon dioxide plus water plus energy to make glucose and oxygen)

Exothermic reaction Many chemical reactions release energy in the

form of heat, light, or sound. These are exothermic reactions.

Exothermic chemical reactions produce heat. Examples

1. In this reaction vinegar is used to remove the protective coating from steel wool, allowing it to rust. When the iron combines with oxygen, heat is released.

Collecting Data

Endothermic Exothermic

Initial Temperature °C °C

Final Temperature °C °C

Temperature change rate

Graphing rate of reaction

Law of Conservation of Mass

CHALLENGE: EXPLAIN WITH EXAMPLE

Law of Conservation of Mass

the mass of substances produced (products) by a chemical reaction is always equal to the mass of the reacting substances (reactants).

in a chemical reaction, the mass of the products equals the mass of the reactants.

Example

1.00g carbon + 5.34g sulphur 6.34g carbon disulphide

Key words: Physical Change

Boiling point Melting point Sublimation Deposition Freezing Evaporation Filtration

Changes in States of Matter

DepositionEvaporationFreezingMeltingSublimation

The Water Profile

Boiling point

temperature at which a liquid changes to a gas

Melting point

the temperature at which a substance changes from a solid to a liquid.

sublimation

the changing of a gas directly to a solid

evaporation

changing of a liquid to a vapor at any temperature below its boiling point.

Salt on snow-covered roads?

If you live in an area with a cold and icy winter, you have probably experienced salt on sidewalks and roads, used to melt the ice and snow and keep it from refreezing.

Salt is also used to make homemade ice cream. In both cases, the salt works by lowering the

melting or freezing point of water. The effect is termed 'freezing point depression'. ”

So, when you add a salt to ice with a little bit of water, the salt lowers the freezing point of the water, keeping it from re-freezing as easily and helping to melt the rest of the ice.

Pressure Cooker Visualizer

Ms Peters cooks rice in a pressure cooker. Why?

A pressure cooker is a sealed pot. Steam trapped inside the pot under pressure

allows the temperature to rise beyond what it could reach normally in a traditional uncovered pot.

As the pressure inside the cooker increases, the boiling point of the water inside increases as well. This causes the food to cook at a higher temperature, which cooks it faster.

CHEMICAL CHANGE PHYSICAL CHANGE

In a chemical change where there is a chemical reaction, a new substance is formed and energy is either given off or absorbed.

A physical change in a substance doesn't change what the substance is.

If a piece of paper is burned, it is broken up into different substances that are not paper.

For example, if a piece of paper is cut up into small pieces it still is paper. This would be a physical change in the shape and size of the paper.

Chemical changes cannot be reversed with the substance changed back without extraordinary means, if at all.

Physical changes can be reversed.

If one made a recipe for a cake with flour, water, sugar and other ingredients and baked them together, it would take extraordinary means to separate the various ingredients out to their original form.

If one decided to mix sugar into water to make sugar water, this would be a physical change as the water could be left out to evaporate and the sugar crystals would remain.

GOOD LUCK!