States of Matter and Acids/Alkalis PDF

# States of Matter - Solids - Usually, solids do not flow or change their shape. - It cannot be compressed. - The volume stays the same. - **Genius:** Can you think of any exceptions to these rules? - Liquids - Liquids can change their shape and flow. - They take the shape of...

# States of Matter - Solids - Usually, solids do not flow or change their shape. - It cannot be compressed. - The volume stays the same. - **Genius:** Can you think of any exceptions to these rules? - Liquids - Liquids can change their shape and flow. - They take the shape of their container, but they don't change their volume. - They cannot easily be compressed. - **Genius:** Can you think of any exceptions to these rules? - Gases - Gases can change their shape and their volume. - They can spread out in all directions. - They can be compressed. - **Genius:** Can you think of any exceptions to these rules? # Properties of Matter - **Physical Property:** A physical property is one that describes how a substance looks and feels. - **Examples:** - **Melting Point:** The temperature at which a solid changes to a liquid. - **Boiling Point:** The temperature at which a liquid changes to a gas. - **Density:** Mass per unit volume - **Strength:** Resistance to breaking or bending. - **Conductivity:** The ability to conduct electricity or heat. - **Chemical Property:** A chemical property is one which describes how a substance reacts with other substances. - **Examples:** - **Reaction with acid:** How a substance reacts when mixed with an acid. - **Flammability:** How easily a substance catches fire. - **Solubility:** The ability of a substance to dissolve in a liquid. - **Physical Change:** A physical change is one where no new substances are formed. - **Examples:** - **State Changes:** Solid to liquid, Liquid to gas, etc. - **Dissolving:** A substance dissolving in a liquid. # Acids and Alkalis - **Do Now:** Name the hazard from the symbol shown. (Symbol is pictured, looks like a skull and crossbones) - **Prior Knowledge:**   - Some chemicals are acids, and others are alkali. - **At KS3**, by definition: - An acid is a substance that reacts with an alkali in a neutralization reaction. - An alkali is a substance that reacts with an acid in a neutralization reaction. - **Acids:** - Acids usually taste sour. - The stronger, or the more concentrated the acid, the greater the hazard. - **Weak Acids:** Irritants - **Strong Acids:** Corrosive, may be very concentrated acids - **Alkalis:** - Alkalis are usually soapy. - **The pH Scale:** - The pH scale gives numbers to acids or alkalis based on their strength. - Often these are matched up to colours, determined by something called Universal Indicator. - **A Neutral Substance:** Is neither acidic nor alkaline. - **Litmus Paper:** - Litmus paper turns red in acids and blue in alkalis. - **Genius:** What is a limitation of Litmus Paper? - It allows you to identify if a substance is an acid or an alkali but does not tell you the strength of the acid or alkali. - **Red Cabbage Indicator:** - Red cabbage juice is another type of indicator. It is very simple and we can make it ourselves. - Red cabbage indicator turns pink in acids, and green in alkalis. # Neutralisation - **Do Now:** Complete the paragraph. - An indicator is a substance which changes color depending on whether something is acid or an alkali. If a substance which is an acid is added to a substance which is an alkali, a *neutralisation reaction* occurs. The indicator will change color to a neutral color. - For example, red cabbage indicator which is in acid, is *pink*. If alkali is added, it turns to a *green* color. Universal indicator which is in acid, is *red*. If alkali is added, it turns to a *purple* color. - **Prior Knowledge:** - Universal indicator gives a range of colors for strong acidic (red) to strong alkaline (purple). - Strong acid = pH 1, weak acid = pH 3, neutral = pH 7, weak alkali = pH 11, strong alkali = pH 14. # Task: Comment on the acidity/alkalinity of the following pHs: - **pH 1:** Strong Acid - **pH 7:** Neutral - **pH 14:** Strong Alkali - **pH 5:** Weak Acid - **Neutralization:** Is a reaction which occurs when an acid and an alkali react together. - **You can also use a pH meter to test the pH of substances to determine if it's an acid or alkali.** - **Genius:** Why is the pH meter a better way to determine the pH of a substance? - Accuracy - User friendly - Safety ==End of Document==